Image decorative processing apparatus

In an image processing apparatus, a matrix for an arbitrary pixel (to be an observed pixel) on the original image is set up so that the density of the observed pixel and that of a target pixel which is located in the direction along which shadows are formed are compared to determine a maximum value of density of the two. If the density of the observed pixel is greater than that of the target pixel or pixels, the density of the target pixel is converted into a predetermined level of density, whereas if the density of the observed pixel is less than that of the target pixel, no conversion of density is made. This procedure is repeatedly performed for the entire image information to thereby create shadows having a designated length and complete a shadowing image. Then, the shadowing image is combined with the original image, whereby a shadowed image is complete.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to an image processing apparatus such as 
digital copiers, facsimiles, printers and the like, and more specifically 
relates to an image processing apparatus in which image information can be 
image-processed into desired features. 
(2) Description of the Prior Art 
In recent years, electrophotographic copiers have come into wide use and 
digital copiers have been put to practical use. With the spread of the 
digital copiers, various kinds of image processing techniques have been 
developed so that an original manuscript can be easily processed using 
such techniques and reproduced as an image-processed duplication. For 
example, Japanese Patent Application Laid-open Hei 4 No. 218,879 discloses 
a prior art image processing apparatus for effecting filling-in treatment, 
outlining treatment, shadowing treatment and the like. 
In the above apparatus, input image data is transformed into binary data by 
way of an image input means and the thus binarized data is stored into 
line memories. When the outlining conversion is to be done, the data in 
these line memories is subjected to an N.times.N matrix logical operation 
to generate binary data representing outlines. When the shadowing 
conversion is to be done, the binary data in the line memories are 
transferred toward 45.degree. direction, right upward to generate 
shadowing data. In these processing, the size of the memory region to be 
used are varied in accordance with the content of the image processing to 
be done. 
In this way, the multi-valued data inputted through the image input means 
in the above apparatus is converted into binary data, which in turn is 
image processed. Accordingly, it was impossible to represent more than two 
tones represented by `0` and `1`, only revealing inferior power of 
expression and poor image quality. That is, it was impossible for the 
above conventional configuration to meet demands of high-quality 
processing when high-quality image was desired to be reproduced at the 
time of image processing. As demand for high-quality images continues to 
expand, it becomes necessary to deal with multi-valued data. The 
multi-valued data, however, is some or several times more massive than the 
binary data, so that the processing time tends to become long. 
Accordingly, image processing having an improved processing efficiency has 
also been desired. The above-mentioned technique was to merely aim at 
improving the utility efficiency of the memories by minimizing the 
required number of dedicated memories when the image processing treatment 
was to be done. That is, no proposal was made in the disclosure to either 
simplify the image processing or improve the quality of images, so that 
the technique can not satisfy the above demands. 
Examples of image processing, not mentioned in the above art, includes a 
halftoning process which is effected in the following manner: That is, in 
order to halftone an image, input image data is analyzed by one pixel to 
another, as shown in FIG.1, in accordance with the following rules: 
(1) if all the pixels 1), 2) and 3) are white (the density is zero), no 
halftoning conversion is done; 
(2) if the pixel 4) or 5) is white (the density is zero), no halftoning 
conversion is done; 
(3) halftoning is effected when either of the above condition (1) or (2) is 
satisfied; and 
(4) the above procedure (1) to (3) is repeated to develop dot patterns 
throughout the whole input image to thereby effect halftoning. 
However, if the whole image is halftoned with dots, the original image 
could be degraded. In order to avoid this degradation, it is necessary to 
check the pixel data to search contour parts in the image so as not to 
halftone the edge parts and therearound. This process, however, takes a 
long time. In consequence, this method cannot meet the requirement in view 
of simplifying the image processing. 
SUMMARY OF THE INVENTION 
In view of what has been discussed above, it is therefore an object of the 
present invention to provide an image processing apparatus which is 
improved in image-processing speed and is able to provide a good image 
free from degradation in image quality. 
A means for solving the problems in accordance with present invention, 
includes: a mode-setup means for designating an image processing mode; a 
matrix-setup means for designating an arbitrary observed pixel and setting 
up a matrix of pixels containing the observed pixel at a center thereof 
and candidate pixels for target pixels around the observed pixel; a 
determining means for determining target pixel or pixels to be compared to 
an observed pixel, in accordance with an image processing mode designated; 
a comparing means for comparing the density between the observed pixel and 
the target pixel or pixels; a converting means for converting the density 
of the target pixel or pixels based on the result of the comparison; a 
means for repeatedly operating each means of image processing over the 
whole image information to generate image information; and a means for 
forming an image by making logical operations between the image 
information generated by the image processing and information on the 
original image, and is constructed such that the mode-setup means sets up 
any one of image processing modes including shadowing, hollowing and 
halftoning modes or a combined image processing mode of the three; and the 
converting means differentiating the density of an observed pixel from 
that of a target pixel or pixels. 
When the shadowing operations is to be made, a means for arbitrary 
selecting a direction of shadows is provided and selection of a target 
pixel is made in such a manner that the target pixel to be selected from 
the candidate pixels around the observed pixel is located in the shadowing 
direction relative to the observed pixel. 
When the shadowing and hollowing operation is to be made, the system 
includes: an expanding means for expanding peripheral pixels around an 
observed pixel on image information as to an original image, in a 
predetermined amount of pixels; a shadowing means for adding shadows 
extending toward a predetermined direction to the image information on the 
image expanded; and an image processing means for removing the image 
information on the original image from the image information on the 
shadowed image. 
When the halftoning operation is to be made, the system includes: an 
expanding means for expanding peripheral pixels around an observed pixel 
on image information as to an original image, in a predetermined amount of 
pixels to create an expanded image; a pattern generating means for 
generating specific image pattern information; a removing means for 
removing the expanded image information from the image pattern 
information; and an image processing means for fitting the original image 
information onto the image pattern information with a portion 
corresponding to the expanded image information removed. 
The means for solving the problems of the invention generally has a 
configuration described above, detailed feature of the present invention 
will be described as follows. 
In accordance with a first aspect of the present invention, an image 
processing apparatus comprises: a mode-setup means for designating an 
image processing mode; a determining means for determining target pixel or 
pixels to be compared to an observed pixel, in accordance with an image 
processing mode designated; a comparing means for comparing the density 
between the observed pixel and the target pixel or pixels; and a 
converting means for converting the density of the target pixel or pixels 
based on the result of the comparison. 
An image processing apparatus in accordance with a second aspect of the 
present invention has the above configuration and further comprises: a 
matrix-setup means for designating an arbitrary observed pixel and setting 
up a matrix of pixels containing the observed pixel at a center thereof 
and candidate pixels for target pixels around the observed pixel; a means 
for selecting a target pixel or pixels from the candidate pixels around 
the observed pixel, in accordance with a setup mode; a means for 
repeatedly operating each means of image processing over the whole image 
information to generate image information; and a means for forming an 
image by making logical operations between the image information generated 
by the image processing and information on the original image. 
In an image processing apparatus in accordance with a third aspect of the 
present invention, the mode-setup means of the first configuration sets up 
any one of image processing modes including shadowing, hollowing and 
halftoning modes or a combined image processing mode of the three. 
An image processing apparatus in accordance with a fourth feature of the 
present invention comprises: a mode-setup means for designating an image 
processing mode; a determining means for determining target pixel or 
pixels to be compared to an observed pixel, in accordance with an image 
processing mode designated; a comparing means for comparing the density 
between the observed pixel and the target pixel or pixels; and a 
converting means for converting the density of the target pixel or pixels 
based on the result of the comparison, and is constructed so that the 
converting means differentiates the density of an observed pixel from that 
of a target pixel or pixels. 
An image processing apparatus in accordance with a fifth aspect of the 
invention has the configuration described in the third configuration 
above, and further comprises a means for arbitrary selecting a direction 
of shadows, and is characterized in that selection of a target pixel is 
made in such a manner that the target pixel to be selected from the 
candidate pixels around the observed pixel is located in the shadowing 
direction relative to the observed pixel. 
In accordance with an image processing apparatus of a sixth aspect of the 
invention, the image processing apparatus has the configuration of the 
fifth aspect described above, and the shadowing operation includes the 
steps of: effecting a logical operation of comparing an observed pixel and 
a shadowing target pixel to take a maximum value of the density of the 
two, the logical operation being repeated for every observed pixel 
throughout the original image; converting the density of shadows to create 
a shadowing image data; and combining the original data with the shadowing 
image data to complete a shadowed image. 
In accordance with an image processing apparatus of a seventh aspect of the 
invention, the image processing apparatus has the configuration of the 
sixth aspect described above, and in effecting the shadowing operation, no 
conversion of density of shadows is effected. 
In accordance with an image processing apparatus of an eighth aspect of the 
invention, the image processing apparatus has the configuration of the 
sixth aspect described above, in effecting the shadowing operation, the 
density of a target pixel is set up at a lower density than that of a 
corresponding observed pixel when the density of shadows is converted. 
In accordance with a ninth aspect of the present invention, an image 
processing apparatus as described in the third aspect, further has a 
system for the shadowing and hollowing mode which includes: an expanding 
means for expanding peripheral pixels around an observed pixel on image 
information as to an original image, in a predetermined amount of pixels; 
a shadowing means for adding shadows extending toward a predetermined 
direction to the image information on the image expanded; and an image 
processing means for removing the image information on the original image 
from the image information on the shadowed image. 
In accordance with an image processing apparatus of a tenth aspect of the 
invention, in the image processing apparatus having the configuration of 
the ninth aspect described above, the shadowing and hollowing operation 
includes the steps of: effecting a logical operation of comparing the 
density of an observed pixel and all expanding target pixels around the 
observed pixel to take a maximum value of those pixels so as to create 
one-dot expanded image, the logical operation being repeated for every 
observed pixel along contour lines throughout the original image to form a 
completely expanded image; shadowing the expanded image; taking a maximum 
value of density of an observed pixel and a shadowing target pixel; 
repeatedly converting the density of shadows based on the result of the 
maximum taking operation between the observed pixel and the shadowing 
target pixel, in accordance with a designated length of shadow, until a 
desired, shadowed and expanded image is formed; and removing the original 
image from the shadowed and expanded image, to complete a shadowed and 
hollowed image. 
In accordance with an image processing apparatus of an eleventh aspect of 
the invention, the image processing apparatus has the configuration of the 
ninth aspect described above, and in effecting the shadowing and hollowing 
operation, no conversion of density of shadows is effected. 
In accordance with a twelfth aspect of the present invention, an image 
processing apparatus as described in the third aspect, further comprises a 
system for the halftoning mode which includes: an expanding means for 
expanding peripheral pixels around an observed pixel on image information 
as to an original image, in a predetermined amount of pixels to create an 
expanded image; a pattern generating means for generating specific image 
pattern information; a removing means for removing the expanded image 
information from the image pattern information; and an image processing 
means for fitting the original image information onto the image pattern 
information with a portion corresponding to the expanded image information 
removed. 
In accordance with an image processing apparatus of a thirteenth aspect of 
the invention, the image processing apparatus has the configuration of the 
twelfth aspect described above, and the halftoning operation includes the 
steps of: effecting a logical operation of comparing an observed pixel and 
all expanding target pixels around the observed pixel to take a maximum 
value of density of those pixels so as to create one-dot expanded image, 
the logical operation being repeated for every observed pixel along 
clearance pixels throughout the original image to form a completely 
expanded image; overlapping a screen pattern on white-data areas of the 
expanded image to form a screen image; and removing the expanded image 
from the screen image and combining the original image onto the screen 
image to complete a halftone image. 
Finally, a fourteenth aspect of the invention resides in an image 
processing apparatus having the configuration of the twelfth aspect 
described above, wherein neither determining operation of taking a maximum 
of density of an observed pixel and expanding target pixels nor expanding 
operation is effected in effecting the halftoning operation. 
As described above, the image processing apparatus of the present 
invention, sets up a matrix for an arbitrary pixel (to be an observed 
pixel) on the original image so that the density of the observed pixel and 
that of a target pixel or pixels which are selected in association with 
the operating mode of image processing are compared to determine a maximum 
value of density of those pixels. If the density of the observed pixel is 
greater than that of the target pixel or pixels, the density of the target 
pixel or pixels is converted into a predetermined level of density, 
whereas if the density of the observed pixel is less than that of the 
target pixel or pixels, no conversion of density is made. This procedure 
is repeatedly performed for the entire image information to thereby create 
a processed image. Then the processed image is combined with the original 
image, whereby a desired image to be aimed in the designated mode is 
complete. 
If an original document has noises such as smudges, dust etc., the 
duplication of the original is degraded in image quality since these 
noises are also image processed. To avoid this, the apparatus compares the 
density of an observed pixel with a predetermined value to thereby 
determine whether the pixel on question is noise or not. If the observed 
pixel is determined as a noise, the image processing for the pixel is 
prohibited to avoid unnecessary image processing, thus making it possible 
to improve the quality of image in the image processing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The instant invention is most clearly understood with reference to the 
following definition(s): 
"Image decorative processing mode" shall be understood to include and mean 
any one of the following image processing modes shadowing mode, hollowing 
mode, halftoning mode, white-shadowing mode, hollow and white-shadowing 
mode, changing line thickness mode as well as other image processing modes 
known in the art such as the character-slanting mode. 
FIG. 2 shows a facsimile built-in digital copier A having an image 
processing apparatus of the present invention. As shown in the figure, the 
digital copier A includes a scanner system 1, a laser printer system 2, a 
multi-sheet tray unit 3 and an automatic sorter 4. 
The scanner system 1 is composed of an original table 5 made of a 
transparent glass, an automatic reversing document feeder (RDF) 6 and a 
scanner unit 7. In the RDF 6, a multiple number of original documents 
placed beforehand, are delivered out one by one to the scanner unit 7 in 
order to allow the scanner unit 7 to pick up the content of document on 
one side or both sides in accordance with the selection by the operator. 
The scanner unit 7 includes a lamp reflector assembly 8 for illuminating 
the document, a plurality of reflection mirrors 10 for introducing the 
reflected light from the document to a photoelectric transfer device (CCD) 
9 and a lens 11 for focusing the reflected light from the original 
document on the surface of the CCD 9, forming a reflected light image. 
The scanner system 1 is configurated so that when the original document 
placed on the original table 5 is to be scanned, the scanner unit 7 moves 
along the underside of the original table 5 in order to pick up the 
original image on the document; when the RDF 6 is used to pick up the 
original image on the document, the original document is moved while the 
scanner unit 7 is stationed at a predetermined position below the RDF 6. 
Image data thus picked up from the original image by means of the scanner 
unit 7 is sent to an image processing system where the image data 
undergoes various processes. The thus processed image data is temporarily 
stored in a memory. Then, the image data is imparted to the laser printer 
system 2 in response to an output instruction, whereby the image is formed 
on a sheet of paper. 
The laser printer system 2 includes a manually sheetfeeding tray 14, a 
laser-writing unit 15 and an electrophotographic processing unit 16 for 
creating images. The laser-writing unit 15 is composed of a semiconductor 
laser 17 emitting laser beams in association with the image data from the 
aforementioned memory, a polygonal mirror deflecting the laser beams at an 
equiangular rate, an f-.theta. lens for correcting the equiangularly 
deflected laser beams so that the laser spot may move linearly at a 
uniform speed on a photoreceptive drum 18 of the electrophotographic 
processing unit 16. 
Arranged around the photoreceptive drum 18 in the electrophotographic 
processing unit 16 are a charger 19, developing unit 20, a transfer unit 
21, a separator 22, a cleaning unit 23, a charge-erasing unit 24 and a 
fixing unit 25. A sheet conveying path 30 is disposed downstream of the 
fixing unit 25 or on the side to which the sheet with image formed thereon 
is discharged from the fixing unit 25. This sheet conveying path 30 is 
branched into two paths: a sheet conveying path 31 which is connected to 
the sorter 4 and another sheet conveying path 32 which is connected to 
multi-sheet tray unit 3. 
The sheet conveying path 32 is further branched in the multi-sheet tray 
unit 3, into two sheet conveying paths, namely a sheet reversing path 33 
and double-side/composition conveying path 34. The sheet reversing path 33 
serves as a sheet conveying path for reversing the sheet rear-side up in 
the double-side copying mode in which copying is effected on both sides of 
the sheet. The double-side/composition conveying path 34 is used to convey 
the sheet from the sheet reversing path 33 to the image forming station at 
the photoreceptive drum 18, in the double-side copying mode. This 
conveying path 34 also severs to convey the sheet without reversing to the 
image forming station at the photoreceptive drum 18, in the one-side 
composition copying mode in which different original images are to be 
composed on one side or different color toners are used to form an image 
on one side. 
The multi-sheet tray unit 3 has first, second and third cassettes 35, 36 
and 37 and further includes a fourth cassette 38 which can be optionally 
added. The multi-sheet tray unit 3 has a common sheet conveying path 39, 
which is arranged so that sheets held in each cassette may be delivered 
from the top, one by one, toward the electrophotographic processing unit 
16. This common sheet conveying path 39 and another sheet conveying path 
40 from the fourth cassette 38, merge in a sheet conveying path 41, on the 
way to the electrophotographic processing unit 16. This sheet conveying 
path 41 is arranged so as to merge with the double-side/composition 
conveying path 34 and the sheet conveying path 42 from the manually 
sheet-feeding tray 14 and to be connected to the image forming station 
between the photoreceptive drum 18 and transfer unit 21 in the 
electrophotographic processing unit 16. That is, the meeting point of 
these three conveying paths is positioned near the image forming station. 
In this arrangement, the laser beams in the laser writing unit 15, as 
modulated based on the image data loaded from the memory, are scanned onto 
the surface of the photoreceptive drum 18 in the electrophotographic 
processing unit 16 to form an electrostatic latent image on the surface. 
The latent image is developed with toner. The visualized toner image is 
electrostatically transferred onto the surface of the sheet delivered from 
the multi-sheet tray unit 3 and fixed thereon in the fixing unit. The 
sheet with the image thus formed is conveyed from the fixing unit 25 to 
the sorter 4 by way of the sheet conveying paths 30 and 31 or sent out to 
the sheet-reversing path 33 by way of the sheet conveying paths 30 and 32. 
Referring next to FIG. 3, configurations and functions of the image 
processing system and other controlling systems contained in the digital 
copier will be described. FIG. 3 is a block diagram showing an image 
processing system and other controlling systems contained in the facsimile 
built-in digital copier A. In the figure, a reference numeral 50 
designates an image data inputting unit which is composed of a CCD portion 
50a, a histogram processor 50b and an error-diffusing processor 50c. A 
reference numeral 51 designates an image processing unit which is composed 
of multi-valuing processors 51a and 51b, an image 
modification/edition/composition processor 51c, a density converting 
processor 51d, a magnification/reduction processor 51e, an image processor 
51f, an error-diffusing processor 51g and a compressing processor 51h. A 
reference numeral 52 designates an image data outputting unit which is 
composed of a restoring portion 52a, multi-valuing processor 52b, an 
error-diffusing processor 52c and a laser outputting portion 52d. 
Reference numerals 53, 54 and 55 designate a memory, a control panel and 
an image processing CPU (central processing unit), respectively. FIG. 4 is 
an enlarged view of the control panel 54 having a LC touch panel 
controlling screen, containing a sheet-tray selecting key 56, 
magnification setting keys 57, copy density setting keys 58, a function 
selecting key 59 and a display portion 60. When the function selecting key 
59 is pressed, the frame of the screen is switched over. 
The image processing system contained in the digital copier A includes the 
image data inputting unit 50, the image processing unit 51, image data 
outputting unit 52, the memory 53 of RAMs (random access memories) etc., 
and the image processing CPU 55. 
The image data inputting unit 50 includes the CCD portion 50a, the 
histogram processor 50b and the error-diffusing processor 50c. The image 
data inputting unit 50 is constructed so as to operate as follows. That 
is, image data, picked up from the original document by means of the CCD 
9, is binarized and processed by creating a histogram based on the binary 
digital quantities. Then, the thus processed image data is temporarily 
stored in the memory 53. That is, in the CCD portion 50a, analog electric 
signals representing image density of the image data are A/D transformed, 
thereafter, the digital signal is subjected to the MTF (modulation 
transfer function) correction, the black and white correction or the gamma 
correction, whereby the output for each pixel is supplied to the histogram 
processor 50b as a digital signal representing 256 tones (8 bits). 
In the histogram processor 50b, density information (represented by 
histogram data) is obtained by adding the number of pixels having the same 
density level by classification of 256 tones. The thus obtained histogram 
data is supplied, as required, to the image processing CPU 55 and sent to 
the error-diffusing processor 50c as pixel data. In the error-diffusing 
processor 50c, the digital signals each having 8 bits per pixel, outputted 
from the CCD portion 50a, are converted into 2 bit (quaternary) signals by 
the error-diffusing method as one kind of pseudo-intermediate processes or 
the method in which quaternarized errors are used to determine 
quaternarizing the neighboring pixels. Then redistributing operations are 
effected in order to faithfully reproduce local area densities in the 
original document. 
The image processing unit 51 includes the multi-valuing processors 51a and 
51b, the image modification/edition/composition processor 51c, the density 
converting processor 51d, the magnification/reduction processor 51e, the 
image processor 51f, the error-diffusing processor 51g and the compressing 
processor 51h. The image processing unit 51 outputs finalized image data 
which is desired by the operator, by converting the input image data in 
conformity with the image processing mode instructed through the control 
panel 54. That is, this processing unit is so constructed as to continue 
to process the input image data until the finally converted output image 
data is entirely stored in the memory 53. Here, each of the 
above-mentioned processors contained in the image processing unit 51 will 
operate as required and should not operate necessarily. 
Specifically, the multi-valuing processors 51a and 51b reconvert the data 
quaternarized in the error-diffusing processor 50c, into 256-valued data. 
The image modification/edition/composition processor 51c, selectively 
effects a logical operation, i.e., logical OR, logical product or 
exclusive OR, for each pixel. This logical operation is executed for the 
image data stored in the memory 53 and bit data from a pattern generator 
(PG). 
The density converting processor 51d sets up, based on a predetermined 
gradation converting table, an arbitrary relation of the output densities 
to the input densities as to the digital signals representing 256 tones of 
density, in accordance with an instruction through the copy density keys 
58 on the control panel 54. 
The magnification/reduction processor 51e effects interpolation based on 
the known data inputted, in conformity with a magnification designated by 
the magnification setting key 57 on the control panel 54, to thereby 
determine pixel data (density value) representing a size-varied pixel with 
respect to size-varied target pixels. Based on the newly determined pixel 
data, the image data is updated by sequentially converting the image data 
in the auxiliary scan direction and thereafter in the main scan direction. 
In the image processor 51f, the pixel data inputted is subjected to various 
kinds of image processing. In addition, the image processor 51f can make a 
collection of information on the data sequences such as feature extraction 
and the like. In the error-diffusing processor 51g effects a similar 
process effected in the error-diffusing processor 50c of the image data 
inputting unit 50. The compressing processor 51h compresses the binary 
data based on a coding scheme called Run Length Coding. On the other hand, 
compressing of the image data is effected in the last processing loop when 
finally outputting image data is completely formed. 
The image data outputting unit 52 includes the restoring portion 52a, the 
multi-valuing processor 52b, the error-diffusing processor 52c and the 
laser outputting portion 52d. The image data outputting unit 52 is 
configurated as follows. The unit 52 restores the compressed image data 
stored in the memory 53 to the original state and reconverts the restored 
data to the original image data having 256 tones of density. Then, the 
image data outputting unit 52 effects error-diffusing based on quaternary 
data with which it is possible to represent more gentle halftoned 
gradations than with binary data. The thus processed data is transferred 
to the laser outputting portion 52d. More specifically, in the restoring 
portion 52a, the image data compressed by the compressing processor 51b is 
restored to the original state. In the multi-valuing processor 52b, a 
similar process to that effected in the multi-valuing processors 51a and 
51b of the image processing unit 51 is performed. In the error-diffusing 
processor 52c, a similar process to that effected in the error-diffusing 
processor 50c in the image data inputting unit 50 is performed. In the 
laser outputting portion 52d, the digital pixel data is converted, based 
on control signals from an unillustrated sequence controller, into 
switching signals for the semiconductor laser 17, so that the 
semiconductor laser 17 is turned on and off. 
Accordingly, in the image processing unit 51, the pixel data which 
represents 256 tones for every pixel is quantized into compressed pixel 
data representing 4 tones for every pixel. The thus quantized image data 
is used to determine the output width (illuminating time) of the laser 
beams from the semiconductor laser 17 for each pixel (one dot). In other 
words, the pixel data having four tones for every pixel is brought into 
gradational representation by varying the output width of the laser beams 
from the semiconductor laser 17. 
The copier A of this embodiment has image processing functions for 
modification and edition of images such as shadowing, hollowing and 
halftoning. That is, as shown in FIG. 5, the copier A includes: a mode 
setup means 70 for selecting an image processing mode from shadowing, 
hollowing, halftoning and combinations of these; an image formation 
controlling means 71 for controlling image forming, based on the image 
information inputted; image processing means 72 for processing the image 
information based on an image processing mode selected; an image 
information inputting means 73 such as the CCD 9 for inputting image data 
to the image formation controlling means 71. Specifically, the mode setup 
means 70 includes function selecting keys and the like on the control 
panel 54. The image formation controlling means 71 embodied by the image 
processing CPU 55, the memory 53 and the like. The image processing means 
72 includes the image processing unit 51, the image data inputting unit 50 
and the image data outputting unit 52. 
The image processing means 72 effects the following basic functions for 
image processing. That is, the image processing means 72 effects: a 
determining function in which the image data picked up by the image 
information inputting means 73 is converted into binary or multi-valued 
data and one or some target pixels to be compared to an observed pixel is 
determined in accordance with an image processing mode selected; a 
comparing function of comparing the density of target pixel or pixels to 
that of the observed pixel; a converting function of converting the 
density of the target pixel or pixels based on the result of the 
comparison; and a function of distinguishing whether the image data on an 
observed pixel is noise, based on the density information of the observed 
pixel and prohibiting the image processing when the data is determined as 
a noise. Here, the observed pixel means a pixel being observed on an 
original and to be image processed while the peripheral pixels indicate 
those enclosing the observed pixel and further the target pixels indicate 
those to be subjected to an image processing such as shadowing and the 
like. 
The means 72 further has functions characteristic of each image processing 
mode. Specifically, the characteristic functions for the shadowing mode, 
includes: a function of stopping conversion of density of target pixels or 
prohibiting the image processing when the density of an observed pixel is 
equal to or less than the shadowing density or when an observed pixel has 
a predetermined quantized density value; a function of differentiating the 
density of a target pixel or pixels from that of an observed pixel when 
the density of the target pixel(s) is converted relative to the observed 
pixel, or particularly a function of reducing the density of the target 
pixel(s) when the shadowing image is to be discriminated from the original 
image; a function of varying the density of shadowing; and a function of 
setting up an arbitrary direction of shadowing in the image information on 
the target pixel(s). To deal with a case where shadowing is effected on an 
image rotated, the means 72 has a function of determining a shadowing 
direction for the image information on the rotated image. Further, in 
order to handle a case where the placing direction of an original document 
does not match that of the transfer paper, the image processing means 72 
has a function of detecting the direction of the original and the 
direction of the transfer paper to compare the directions each other and 
rotating the image information if the directions differ; a function of 
determining, based on the rotated direction of the image, a direction of a 
target pixel or pixels to be shadowed with respect to an observed pixel; 
and a function of comparing the density of the determined target pixel(s) 
relative with the observed pixel and converting the density of the target 
pixel(s). 
For the hollowing mode, the image processing means 72 effects: a function 
of expanding peripheral pixels of an observed pixel in a predetermined 
amount; and a function of removing the original image information from the 
expanded image information by effecting logical operations. For the 
shadowing and hollowing mode, the image processing means 72 effects: a 
function of expanding peripheral pixels around an observed pixel in a 
predetermined amount; a function of creating shadows in a predetermined 
direction on the image information after the expansion; and a function of 
removing the original image information from the expanded image 
information by effecting logical operations. If, in the shadowing and 
hollowing mode, the density of the target pixel(s) is to be converted 
relative to the observed pixel, the means 72 further has a function of 
differentiating the density of the target pixel(s), particularly 
increasing the density of the target pixels in order to enhance sharpness 
of the contour; and a function of stopping conversion of density of the 
target pixels or prohibiting the image processing when an observed pixel 
has a predetermined quantized density value. 
For the halftoning mode, the means 72 has a function of expanding 
peripheral pixels around an observed pixel in a predetermined amount; a 
function of preparing particular image pattern information; a function of 
removing the image information after the expansion from the prepared image 
pattern information; a function of fitting the original image information 
onto the image pattern information with the image information of the 
expanded image removed, by effecting logical operations; and a function of 
sequentially effecting expanding operations for every pixel without 
effecting expansion of the image information when the density of an 
observed pixel is lower than a predetermined quantized value. 
Now, practical procedures for effecting each of the image processing will 
be described. In the beginning, when the function selecting key on the 
control panel 54 is pressed in order to select one of the image processing 
modes, a setup frame for the halftoning mode is displayed as shown in FIG. 
6. Further pressing of the function selecting key causes the display to 
present another setup frame for the shadowing and hollowing mode, as shown 
in FIG. 7. This setup frame displays three modes, i.e., the shadowing 
mode, the shadowing and hollowing mode and the hollowing mode so as to 
allow an user to select one mode from these. 
When the user selects the shadowing mode, the user should place an original 
on the original table 5 or on the original feeder (RDF) 6 and press the 
copy start key. As the operation starts, the scanner unit 7 picks up the 
original image from the document placed. The image data thus picked up is 
stored into the memory 53 through the image data inputting unit 50, so 
that various processing may be made in the image processing unit 51. 
Initially, the image data is quantized into quaternary data in the 
error-diffusing processor 50c in the image data inputting unit 50. The 
thus quantized data is stored into the memory 53 and made to pass through 
the multi-valuing processor 51a without being converted into 256-valued 
data by the multi-valuing process. When the shadowing mode is selected, 
the image data is image-processed in the image 
modification/edition/composition processor 51c by a 3.times.3 matrix as 
shown in FIG. 8. This matrix is well-known and is the one normally used in 
the art. In this image processing, a code is set up to take a maximum 
value of density between an observed pixel E and a target pixel I. That 
is, the processor 51c is operated so as to compare the density between the 
pixels E and I. If the density of the pixel E (D.sub.E) is not less than 
that of the pixel I (D.sub.I) or D.sub.E .gtoreq.D.sub.I, D.sub.I will be 
replaced by D.sub.E ; and if the density of the pixel E (D.sub.E) is less 
than that of the pixel I (D.sub.I) or D.sub.E &lt;D.sub.I, D.sub.I will not 
be modified. 
The original-image data as shown in FIG. 9 is supplied to the 3.times.3 
matrix filter in the order of (0,0), (1,0) . . . (12,12), (13,12). A line 
buffer is placed before the filter. In this arrangement, the filter 
becomes able to start processing the data only when first three lines are 
inputted to the line buffer. The filter is preset so as to take a maximum 
value of D.sub.E and D.sub.I with the other pixels masked, as shown in 
FIG. 10A. The data is supplied from the top left to the bottom right. In a 
case shown in FIG. 10B, the observed pixel E has a density of level `3` 
and the shadowing target pixel I has a density of level `0` while the 
other pixels are being masked. Hence the maximum value thereof is 
determined to be `3` so that the shadowing target pixel I is outputted 
with a density of level `3`. As the shadowing target pixel I having a 
density of level `3` is outputted, the density converting processor 51d 
converts the density of the shadow, so that the shadowing density is 
converted as, to be, for example, `1`. This procedure is repeated to sweep 
the whole image frame, whereby a shadow image displaced by one dot toward 
45.degree. right below from the original image can be formed as shown in 
FIG. 11. In the final stage, the image modification/edition/composition 
processor 51c combines the thus formed shadow image data with the original 
image data stored in the memory 53, to thereby complete the shadowing 
process. The thus generated image data is supplied from the image data 
outputting unit 52 to the laser printer system 2, which in turn completes 
an output image having a one-dot shadow as shown in FIG. 12. 
In the above shadowing operation, the length of the shadow or how many dots 
of shadow is to be formed, is determined by the number of repeating the 
image loop. For example, if the printer has a resolution of 400 dpi and 
shadows of 0.5 mm in length are desired, the image loop should be repeated 
eight times to complete the image data with the desired shadow. When 
shadows of 1 mm are to be formed, the image loop should be repeated 
sixteen times although a longer processing time is required for the 
increase. Here, although the foregoing description of the embodiment has 
been made with reference to the quaternary data, the processing can be 
done for binary data or data representing 256 values. In this connection, 
if quaternary data is applied to 256-valued data, `0`,`1`,`2` and `3` are 
converted into `0`, `85`, `170` and `255,` respectively. 
The above shadowing process can be summarized by the following algorithm: 
(1) Create a shadowing image from an original image by deleting all 
observed pixels E having a density of level `1` in original image data 
(FIG. 13A). 
(2) Compare the density of each observed pixel E with that of a 
corresponding target pixel I to determine the maximum density of the 
pixels. 
(3) Convert the shadow density based on the maximum density. 
(4) Repeat the above procedures (1) and (2) certain times in accordance 
with a specified length of shadow to complete the creation of a shadowing 
image (FIG. 13B). 
(5) Synthesize the shadowing image with the original image to complete the 
shadowed image (FIG. 13C). 
As will be described later, in order not to emphasize noises and not to 
degrade image elements having relatively low-density medium gradations, 
any pixel having a density of not greater than level `1` (D.sub.E 
.ltoreq.1) is assumed to be a noise and any pixel having a density of 
level `2` or greater (D.sub.E .gtoreq.2) will be shadowed. Specifically, 
when the tone or density of an observed pixel is `3` or `2`, the shadowing 
pixel will be shaded in level `1`; when the tone of an observed pixel is 
`1` or `0`, the destiny of the shadowing pixel will be unshaded or shaded 
in level `0`. 
Nevertheless, when, in the above image processing, an original containing a 
halftone, i.e., medium gradations or colored characters other than those 
in black is tried to be copied while a shadowing process shown in FIG. 14 
being effected, the following problems occur. That is, since the shadowing 
process shown in FIG. 14 creates shadows having a shadowing density of 
level `2`; regardless of whether an observed pixel E has a density of 
level `1` or `2`, the density of the corresponding target pixel I will be 
converted into level `2`. Accordingly, the halftoned or medium-toned 
picture also is shadowed only to be spoiled, or the colored characters 
other than those in black also are shadowed so that the characters blur or 
become thick. To avoid this, the system is adapted to compare the density 
of every observed pixel E with that of a corresponding shadow-target pixel 
I when the shadowing pixel I would have been determined to have a density 
of level `2`. If the shadowing density is greater than the density of the 
observed pixel E, the system is adapted so as not to effect any shadowing 
density conversion. In this example, although the shadowing density is 
assumed to be level `2`, the shadowing density could be varied. In this 
way, since observed pixels having light tones are not shadowed, neither 
blur nor thickness does occur in the image, or any halftone image is not 
spoiled either. Accordingly, it is possible to make duplications free from 
degradation of images. 
Meanwhile, when copying is effected with an original document having 
smudges and/or using the original table 5 smeared, invisible small dust 
(or noises) could be picked up as image data, whereby even the noises are 
shadowed. Specifically, as shown in FIG. 16A, a smudge D is added with a 
one-pixel shadow. If shadows of 0.5 mm in length is created, the smudge D 
will be attached with a shadow of eight pixels. Thus, unessential noises 
tend to be emphasized. To avoid this tendency, the processing scheme will 
be set up as follows, by considering that noises made by small dirt and 
dust are low in density. That is, a threshold quantized density is set up 
for observed pixels E so that low-density pixels may be neglected to be 
shadowed. Here, the threshold density is set at level `1`. When an 
observed pixel E has a density of level `1`, the system stops the 
comparison between the observed pixel E and the target pixel I for 
determining the maximum of the two and the shadowing density conversion. 
When copying operation is effected based on the scheme, the smudge D is 
not shadowed as shown in FIG. 16B. Although the above threshold density is 
set at level `1`, this can be varied. FIG. 17A shows a copy sample created 
based on the above scheme. As is apparent from the sample, no noises made 
by dirt and smudges etc., are shadowed and emphasized, therefore it is 
possible to make a natural duplication free from degradation of images. 
This scheme is particularly effective in duplicating an original document 
containing high-density characters and relatively bigger characters. 
In place of the above embodiment in which it is possible to prohibit 
shadowing for noises by taking advantage of the fact that the density of 
dust and the like is low, shadowing for noises may be prohibited by taking 
advantage that dust and the like are isolated. That is, when an image 
shown in FIG. 18A is picked up, noises due to dust etc., are discriminated 
as follows. Initially, in order to avoid misjudgment between noises and 
characters, a 3.times.3 matrix filter is set up in such a manner as shown 
in FIG. 19 that the observed pixel E has a density of level `1` while the 
other enclosing pixels have a density of level `0`. When an observed pixel 
E has a density of level `1`, the system compares the density between the 
observed pixel E and the shadowing target pixel I to determine the 
maximum. In this case, if all the enclosing pixels have a density of the 
predetermined level (i.e., `0`) and the density of the observed pixel E is 
lower than the threshold density (i.e., `1` in this embodiment), the 
system determines that the observed pixel E in question is a noise and 
will not effect shadowing density conversion for the pixel. As a result, 
the shadowing operation is done expect isolated smudges of a single pixel, 
as shown in FIG. 18B. In this way, it is possible to discriminate noises 
due to dust etc., from valid image elements. As a result, it is possible 
to create a natural duplication free from degradation of images without 
noises emphasized. This method is particularly effective in duplicating an 
original document containing small characters. 
On the other hand, if the density of shadows is set close to that of the 
original image, it becomes difficult to discriminate the shadow from the 
original image. Alternatively, if the density of shadows are set darker 
than that of the original image, the character and shadow appear reversed 
to make characters look thicker and blurred, to thereby degrade the image 
quality of the shadowed image. Therefore, the density of the shadowing 
pixel I should be set to be lower than that of the observed pixel E in 
converting the density of target pixels. FIG. 20 shows examples of the 
relation between the density of the observed pixel E and the target pixel 
I, in which a density relation D.sub.E &gt;D.sub.I holds. This setup 
condition makes clear the distinction between the original image and the 
shadowing image to create a good copy output. 
In this copier, it is possible to create a shadow in other positions than 
the position described above or extending 45.degree. right below as well 
as to adjust the density of shadow. For example, it is possible to set up 
a condition of creating a shadow extending 45.degree. left below, through 
the setup frame for the shadowing and hollowing mode. In this condition, a 
pixel designated by G in FIG. 21A becomes a new target pixel relative to 
the observed pixel E. As in the manner described referring to FIG. 11, a 
maximum should be determined from these pixels in the filter. Since the 
observed pixel E has a density of level `3` and the shadowing target pixel 
G has a density of level `0` while the other pixels are being masked, the 
maximum value thereof is determined to be `3` so that the shadowing target 
pixel G is outputted with a density of level `3`. In consequence, an 
shadowing image is formed as shown by a hatched portion in FIG. 21B. As 
the shadowing target pixel G is outputted with the density of level `3`, 
the density converting processor 51d converts the density of shadow in 
accordance with a converting table (shown in FIG. 22) in which converted 
values are related with the density levels. FIG. 22 shows an example in 
which the density of shadow is fixed at level `2`. When a lighter shadow 
is to be added, the density of shadow is converted in accordance with a 
converting table shown in FIG. 23 in which the density of shadow is fixed 
at level `1`. The above process is repeated until the shadow becomes a 
designated length. The thus formed shadowing image is composed on the 
original image to thereby complete the shadowing process. When shadows 
extending 45.degree. left above is to be made, it is possible to create a 
shadow extending 45.degree. left above as shown in FIG. 24B by using a 
matrix filter shown in FIG. 24A. In this way, it is possible for the user 
to create various kinds of shadows extending in a desired direction, by 
selecting a different target pixel from the matrix filter and allowing the 
selected pixel to make logical operations with the observed pixel E. It is 
also possible for the user to select a desired density of shadows. The 
combination of these features enables the copier to create a great variety 
to the images. 
As another mode for image processing and edition, the copier has a 
repeat-copy function, as illustrated in FIG. 25. This mode can be set up 
through the function selecting key on the control panel 54 and allows, for 
example, an A4-sized original document to be repeatedly reproduced in 
(2.times.4) or eight sections on A4-sized paper. Now, let us consider a 
case where an original is reproduced in the repeat-copy mode while shadows 
extending 45.degree. right below relative to the original document are 
created. In this case, when the image processing CPU 55, which controls 
the whole copier, instructs the image to rotate, the operation is 
performed in the following manner. That is, as the operator places an 
A4-sized original document on the original table 5 or the original 
document feeder (RDF) 6, the original-size detector detects the size of 
the original document and recognizes it as A4. Since, in this mode, the 
A4-sized original is designated to be reproduced in 2.times.4 or eight 
sections on a sheet having the same size, i.e., A4 paper, it is naturally 
impossible to fit copy images into the sheet if no data processing is 
made. In order to fit the repeated copy images within the frame, the image 
processing CPU 55 instructs the image processing means 72 to change the 
size of the image and to make a rotation of the image. An image on the 
original placed is processed through the image data inputting unit 50 and 
is stored as image data into the memory 53 so that further various process 
may be done in the image processing unit 51. More specifically, initially, 
the image data is quantized into quaternary data through the 
error-diffusing processor 50c in the image data inputting unit 50 and the 
quantized data is stored temporarily in the memory 53. Then, the image 
processing CPU 55 rotates the image data clockwise 90.degree.. The thus 
rotated image data is again stored into the memory 53. The multi-valuing 
processor 51a converts the image data into 256-valued data. Then, the thus 
processed data is varied as to magnification in the 
magnification/reduction processor 51e so that all the repeated images may 
be fitted within the frame. Thereafter, the data is reconverted into 
quaternary data in the compressing processor 51h so as to temporarily be 
stored in the memory 53. Subsequently, the image processing CPU 55 loads 
the reduced data stored in the memory 53 and repeats it eight-fold to 
create developed image data representing 2.times.4 sections as designated. 
The thus developed data is stored into the memory 53. 
In this process, if the image data is added with shadows as it is, the 
image is reproduced with shadows extending 45.degree. right below as shown 
in FIG. 26. To obtain properly shadowed image, the shadowing target pixel 
I is replaced by the pixel G when the shadowing process in this mode is 
effected. Then, the thus processed data is subjected to the shadowing 
density conversion in the density converting processor 51d so that the 
density of shadows is converted at the fixed tone level `1`, for example. 
As this process is effected throughout the frame, the image is added with 
shadows of one-dot length left below as shown in FIG. 27. In this case, if 
the resolution is 400 dpi and shadows of 0.5 mm in length are desired, the 
above procedure should be repeated eight times to complete the image data 
with the desired shadow. In the final stage, the image 
modification/edition/composition processor 51c combines the thus formed 
shadow image data with the original image data stored in the memory 53, to 
thereby complete the shadowing process. The thus generated image data is 
supplied from the image data outputting unit 52 to the laser printer 
system 2 to complete the operation. In this way, even if the image is 
rotated, shadows in the same positions with those formed when the image is 
not turned, can be added by changing the selection of the shadowing target 
pixel, whereby it possible to obtain an image free from incongruity. 
As a function for image processing and edition, the copier has a mode in 
which an image can be rotated so as to be fitted within the frame of a 
sheet when the way an original document is laid differs from that of the 
paper. 
For example, when an original shown in FIG. 9 laid in a different direction 
relative to the normal position is added with shadows extending 45.degree. 
right below, the operation is effected without any particular 
modification, shadows extending 45.degree. right below will be formed on 
the output image as shown in FIG. 26. The output image, however, has 
shadows extending 45.degree. right above when it is viewed in the same 
position as the original document. 
To deal with the above situation, the following image processing is made. 
That is, when the user sets up the shadowing mode through the control 
panel 54 and places the A4-sized original in the reduction position (to be 
referred to as A4R original, hereinbelow), as shown in FIG. 9, on the 
original table 5 or the original document feeder (RDF) 6, the 
original-size detector detects the original size and position and 
determines it as A4R original. In this condition, when all the cassettes 
35, 36 and 37 hold A4-sized sheets in the normal position, the image 
outputted is naturally cut off unless any treatment is made. To avoid the 
situation, the image processing CPU 55 compares the sheet size and its 
placement with those of the original document, based on the detected 
result of the size of the original and information on sheet size 
automatically detected when the cassettes are attached. If the CPU 55 
determines that the placement of the original differs from that of the 
paper, the CPU 55 instructs the image processing means 72 to rotate the 
image. 
Specifically, an image on the original placed is processed through the 
image data inputting unit 50 and stored as image data into the memory 53 
so that further various process may be done in the image processing unit 
51. Initially, the image data is quantized into quaternary data through 
the error-diffusing processor 50c in the image data inputting unit 50 and 
the quantized data is stored temporarily in the memory 53. Then, the image 
processing CPU 55 rotates the image data clockwise 90.degree.. The thus 
rotated image data is again stored into the memory 53. Then, the data is 
made to pass through the multi-valuing processor 51a without being 
converted into 256-valued data by the multi-valuing process. Subsequently, 
this image data is subjected to the same shadowing process as effected in 
the above-described repeat-copy operation, to thereby complete an image 
with shadows as shown in FIG. 27. On the other hand, when the image is to 
be rotated counterclockwise 90.degree., the shadowing target pixel C may 
and should be selected. Thus, in this configuration, even if the placement 
of the original does not match the placement of the paper in the shadowing 
mode, not only the image data can be rotated but also it is possible to 
select a different shadowing target pixel in conformity with the rotation 
of the image data. Hence, it is possible to create shadows in the same 
position as in the image unrotated. In consequence, it is possible to 
create a duplication with shadows in a desired direction without 
considering the placing direction of the original, whereby it is possible 
to attain improved operating performances. 
Next, when the shadowing and hollowing mode is selected, an original image 
is picked up by the scanner unit 7 from a document placed on the original 
table 5 or the document feeder 6. The picked up image data is stored into 
the memory 53 through the image data inputting unit 50, so that further 
various process may be done in the image processing unit 51. Initially, 
the image data is quantized into quaternary data in the error-diffusing 
processor 50c in the image data inputting unit 50. The thus quantized data 
is stored into the memory 53 and made to pass through the multi-valuing 
processor 51a without being converted into 256-valued data by the 
multi-valuing process. The image data is then image-processed in the image 
modification/edition/composition processor 51c using the 3.times.3 matrix 
as shown in FIG. 8. The original-image data as shown in FIG. 9 is supplied 
to the 3.times.3 matrix filter in the order of (0,0), (1,0) . . . (12,12), 
(13,12). A line buffer is placed before the filter. In this arrangement, 
the filter becomes able to start processing the data only when first three 
lines are inputted to the line buffer. The filter is so set up as to have 
a code for taking a maximum value of density among an observed pixel E and 
peripheral pixels A, B, C, D, G, H and I. 
Referring now to FIG. 10B, in order to take a maximum value of density 
among an observed pixel E and peripheral pixels A, B, C, D, G, H and I as 
expanding target pixels, the system determines that the observed pixel A 
and expanding target pixels A, B and H have a density of level `3` while 
the other pixels have a density of level `0`. Accordingly, the maximum 
value is determined to be `3`, so that the density of all the expanding 
target pixels is set at level `3`. Repeated operations of the above 
process throughout the whole frame of the image, generate a one-pixel 
expanded image as shown in FIG. 28. Then, the thus generated image is 
subjected to the shadowing treatment. As a result, an expanded image with 
shadows having a converted density of level `2` is formed as shown in FIG. 
29. In the final stage, the image modification/edition/composition 
processor 51c removes the original image stored in the memory 53 from the 
expanded image with shadows so that an shadowed and hollowed image is 
formed as shown in FIG. 30. The thus generated image data is supplied from 
the image data outputting unit 52 to the laser printer system 2, which in 
turn outputs a hollowed image with one-dot shadow. 
The above shadowing and hollowing process can be summarized by the 
following algorithm: 
(1) Create a hollowed image from an original image by deleting any observed 
pixel E having a density of level `1` in original image data. 
(2) Compare the density of an observed pixel E with all the peripheral 
pixels A, B, C, D, G, H and I to determine the maximum and create a 
one-dot expanded image section from the observed pixel E. 
(3) Repeat the above step (2) along boundary pixels to complete an expanded 
image. 
(4) Create a shadow for the expanded image. 
(5) Compare the density of each observed pixel E with that of a 
corresponding target pixel I to determine the maximum density of the 
compared pixels. 
(6) Convert the shadow density based on the maximum density. 
(7) Repeat the above procedures (5) and (6) certain times in accordance 
with a specified length of shadow to complete the creation of a shadowing 
image. 
(8) Cut out the original image from the expanded image with shadows. 
Here, in order not to emphasize noises, any image data having a density of 
less than level `1` is assumed to be image noises and only the data having 
a density of level `2` or more is used to effect the hollowing operation. 
When only hollowing treatment is to be made, after the above steps (1), (2) 
and (3), the following step is done as step (4): 
(4) Cut out the original image from the expanded image to complete a 
hollowed image. 
Since an image loop for the expanding treatment creates onedot contour 
lines, the loop may and should be repeated twice to create two-dot contour 
lines. 
Meanwhile, when copying is effected with an original document having 
smudges and/or using the original table 5 smeared, invisible small dust 
(or noises) could be picked up as image data, whereby even the noises are 
expanded (and hollowed). Specifically, as shown in FIG. 31B, if an 
invisible smudge (noise) D is expanded (and hollowed) and added with 
one-pixel shadows, the resulting image becomes as shown in FIG. 31B. If 
the smudge is added with shadows having a length of 0.5 mm, the resulting 
image becomes as shown in FIG. 32B, or smudges (noises) are added with 
shadow having 8 pixels in length to thereby create noises emphasized. To 
avoid this situation, the processing scheme will be set up as follows, by 
considering that noises made by small dirt and dust are low in density. 
That is, a threshold quantized density is set up for observed pixels E so 
that low-density pixels may be neglected to be shadowed. Here, the 
threshold density is set at level `1`. When an observed pixel E has a 
density of level `1`, the system stops the comparison between the observed 
pixel E and the target pixel I for determining the maximum of the two and 
the shadowing density conversion. When copying operation is effected based 
on the scheme, the smudge D is not shadowed and hollowed as shown in FIGS. 
33A and 33B. Although the above threshold density is set at level `1`, 
this can be varied. In this way, no noises made by dirt and smudges etc., 
are shadowed and hollowed, or emphasized, therefore it is possible to make 
a natural duplication free from degradation of images. This scheme is 
particularly effective in duplicating an original document containing 
high-density characters and relatively bigger characters. 
Since it is hard to discriminate smudges from an original image when the 
original document contains small characters and colored characters other 
than those in black, the above measure does not work enough. In such a 
case, if a document has an image as shown in FIG. 34A, it is useful to 
discriminate smudges by taking advantage that dust and the like are 
isolated. That is, initially, in order to avoid misjudgment between noises 
and characters, a 3.times.3 matrix filter is set up in such a manner as 
shown in FIG. 19 that the observed pixel E has a density of level `1` 
while the other enclosing pixels have a density of level `0`. When an 
observed pixel E has a density of level `1`, the system compares the 
density between the observed pixel E and the peripheral pixels to 
determine the maximum of them. In this case, if all the enclosing pixels 
have a density of the predetermined level (i.e., `0`) and the density of 
the observed pixel E is lower than the threshold density (i.e., `1` in 
this embodiment), the system determines that the observed pixel E in 
question is a noise and will not effect shadowing density conversion for 
the pixel. As a result, the expanding and shadowing operation is done 
expect isolated smudges of a single pixel, as shown in FIG. 34B, to 
thereby output an image shadowed and hollowed as shown in FIG. 34C. In 
this way, it is possible to discriminate noises due to dust etc., from 
valid image elements. As a result, it is possible to create a natural 
duplication free from degradation of images without any noises emphasized. 
This method is particularly effective in duplicating an original document 
containing small characters or an original of light tones. 
The above two kinds of treatments can be applied to the hollowing mode. In 
the first treatment, an image shown in FIG. 35A is processed as shown in 
FIG. 35B and converted into a hollowed image as shown in FIG. 35C. In the 
second treatment, an image shown in FIG. 36A is processed as shown in FIG. 
36B and converted into a hollowed image as shown in FIG. 36C. Since any 
noises formed by dirt and smudges are not hollowed as apparent from the 
samples shown in FIGS. 37A, B, it is possible to create a natural 
duplication free from degradation of images without any noises emphasized. 
In this way, since a shadowed and hollowed image is formed by cutting out 
an original image from an image expanded and shadowed from the original 
image; if the density of the shadow after the density conversion is set at 
as low as that in the shadowing mode, for example, level `1`, the outline 
becomes unclear. To avoid this, the shadow after the density conversion 
should be set at a greater level, for example `2`. With this setup, the 
outline appears sharp, thus making it possible to create a good 
duplication result. 
Next, when the halftoning mode is selected, image data picked from an 
original is stored into the memory 53 through the image data inputting 
unit 50, so that further various process may be done in the image 
processing unit 51. Initially, the image data is quantized into quaternary 
data in the error-diffusing processor 50c in the image data inputting unit 
50. The thus quantized data is stored into the memory 53 and made to pass 
through the multi-valuing processor 51a without being converted into 
256-valued data by the multi-valuing process. The image data is then 
image-processed in the image modification/edition/composition processor 
51c using the 3.times.3 matrix as shown in FIG. 8. The original-image data 
as shown in FIG. 9 is supplied to the 3.times.3 matrix filter in the order 
of (0,0), (1,0) . . . (12,12), (13,12). A line buffer is placed before the 
filter. In this arrangement, the filter becomes able to start processing 
the data only when first three lines are inputted to the line buffer. The 
filter is so set up as to have a code for taking a maximum value of 
density among an observed pixel E and peripheral pixels A, B, C, D, G, H 
and I. 
Referring now to FIG. 10B, in order to take a maximum value of density 
among an observed pixel E and peripheral pixels A, B, C, D, G, H and I as 
expanding target pixels, the system determines that the observed pixel E 
and expanding target pixels A, B and H have a density of level `3` while 
the other pixels have a density of level `0`. Accordingly, the maximum 
value is determined to be `3`, so that the density of all the expanding 
target pixels is set at level `3`. Repeated operations of the above 
process throughout the whole frame of the image, generate a one-pixel 
expanded image as shown in FIG. 38. A screen pattern as shown in FIG. 39A 
is developed to form a screen image as shown in FIG. 39B. As the above 
expanded image is cut off from the screen image and then the resulting 
image is combined with the original image so as to provide a halftoned 
image as shown in FIG. 40. The thus generated image data is supplied from 
the image data outputting unit 52 to the laser printer system 2, which in 
turn outputs a one-dot halftoned image. 
The above halftoning process can be summarized by the following algorithm: 
(1) Compare the density of an observed pixel E with all the peripheral 
pixels A, B, C, D, G, H and I to determine the maximum and create a 
one-dot expanded image section from the observed pixel E. 
(2) Repeat the above step (1) along boundary or clearance pixels to 
complete an expanded image. 
(3) Overlap a screen pattern on the white-data areas of the expanded image 
to form a screen image. 
(4) Combine the original image onto the screen image to complete a halftone 
image. 
The above procedure halftones only the white data areas of the expanded 
image but will not dot the black data areas (halftone or edges). 
Accordingly, clearances appear around the black data areas. In the 
conventional halftoning process of this kind, since the whole image used 
to be dotted, the original image would be degraded. Alternatively, in 
order not to deteriorate the original image, edges should have been 
detected to avoid halftoning the areas which were determined as edges. 
Therefore, this process required much time. In contrast to this, since the 
process of the invention does not halftone the original image, it is 
possible to obtain good duplications. Since the process is so simple that 
it is possible to improve processing efficiency and therefore reduce the 
processing time. 
When copying is effected with an original document having smudges as shown 
in FIG. 41a and/or using the original table 5 smeared, small smudges D 
also undergo the expanding conversion as shown in FIG. 41B, and 
consequently, the smudges D also used to be halftoned as shown in FIG. 
41C, resulting in unnatural output. To avoid this situation, the 
processing scheme will be set up as follows, by considering that noises 
made by small dirt and dust are low in density. That is, a threshold 
quantized density is set up for observed pixels E so that low-density 
pixels may be neglected to be shadowed. Here, the threshold density is set 
at level `1`. When an observed pixel E has a density of level `1` or less, 
the system stops the comparison between the observed pixel E and the 
target pixel I for determining the maximum of the two and the expanding 
process. Accordingly, the expanded image created becomes as shown in FIG. 
42A. The thus expanded image is overlapped with a screen pattern to form a 
screen image, which in turn combined with the original image to complete a 
halftone image as shown in FIG. 42B. In this way, it is possible to 
halftone noises made by dirt and smudges etc., which would be not 
halftoned but emphasized by clearances if the above noise reduction scheme 
was not adopted. As a result, it possible to produce good duplications 
free from degradation of images. 
As has been described heretofore, in the conventional image processing, 
when shadowing and expanding processes are to be done, it was necessary 
that the CPU should search all the pixels having densities and extract 
widths of the picture elements in order to calculate the size of shadows 
and line widths for expansion. Accordingly, it would take a longer 
processing time as the image to be handled becomes complicated. In 
contrast, it is possible for the present invention to attain high-speed 
processing since the shadowing and expanding operation can be done by only 
the simple convolution operation for images, without regarding type of 
images. Therefore, the image processing of any images, even if 
complicated, can be done within a short period of time. Further, without 
needing any complicated processing, it is possible to eliminate noises 
which are generated by smudges on the original or dirt and dust of the 
original table or by any other factors and would be emphasized in the 
conventional processing. In consequence, it is possible to improve quality 
of images in the copying operation of this kind. 
It is noted that the present invention should not be limited to the above 
specific embodiments, but many changes and modifications may of course be 
added to the above embodiment within the spirit and scope of the 
invention. For example, in place of lowering the density of the target 
pixel, it is possible to set up the density of the target pixel at a 
greater level than that of the observed pixel, if the shadow is desired to 
be intensified. It is also possible to set up the density of the image 
created by the image processing at any dark or light level. Alternatively, 
it is possible to add tones even within a single frame of image. Moreover, 
any combination of image processing modes can be selected. Other examples 
of image processing modes include a mode for changing the thickness of 
lines, a mode for white-shadowing and a mode for hollowing and 
white-shadowing. 
As has been apparent from the above description, in accordance with the 
present invention, since the method of image processing can be simplified, 
it is possible to handle even a complicated image within a short period of 
time. Therefore, it is possible to realize high-speed processing, 
regardless of type of images. Further, since all the image processing 
modes can be effected in the similar manner, it is possible to improve 
efficiency of the image processing. 
In accordance with the present invention, since the density of the target 
pixel can be varied in accordance with the tone of an original image 
handled, a faithful reproduction of an original image can be created in 
the processed image, without being degraded in its quality of image. 
Further, it is possible to emphasize an original image and if the original 
contains halftoned portions, it is possible to create a great variety to 
the reproduced image, without degrading quality of the original image. 
In accordance with the present invention, desired shadows by the user can 
readily be formed, it is possible to create a great variety to the image. 
In the conventional processing, it was necessary to expand an image from an 
original, remove the original image from the expanded image and create 
contour lines before effecting a shadowing operation. In the present 
invention, however, shadows are formed by shadowing the expanded image and 
removing the original image from the expanded and shadowed image. As a 
result, the processing can be simplified, thus realizing improved 
processing efficiency and reduced processing time. 
Since, unlike the prior art, all the image of an original is not dotted 
when the original image is to be halftoned, it is possible to obtain a 
well-reproduced image without any features of the original image degraded. 
Besides, since the configuration of the present invention does not need to 
search edge portions, it is possible to realize improved processing 
efficiency and reduced processing time.