Abstract:
A color image processing apparatus for digitally reading a color document and effecting digital printing comprises a character region extracting device for extracting a character region of the color document; a black portion extracting device for extracting a black portion of the color document; and a single black color processing device for processing a single black color only with respect to a region which falls within the character region and the black portion in the color document, so as to allow character portions to be distinguished favorably.

Description:
This application is a continuation of application Ser. No. 08/155,531 filed Nov. 22, 1993, now abandoned, which is a continuation application of Ser. No. 07/911,367, filed Jul. 13, 1992, abandoned, and which is a continuation application of Ser. No. 07/173,654, filed Mar. 25, 1988, abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a color image processing apparatus. 
     2. Related Background Art 
     In the conventional color digital image processing that is undertaken in digital color copying machines, digital color facsimile equipment and the like, full color images are obtained by using four colored inks of yellow, magenta, cyan and black in accordance with a subtractive color mixing process. 
     With respect to the black-color portions of a document, it is necessary to selectively use the black that is formed by superposing the three colors of yellow, magenta and cyan and the black that is formed by using the black ink alone. 
     In the undercolor removal (UCR) process which is conventionally employed in printing and the like, the minimum values of yellow, magenta and cyan are calculated as the black color, and the amount of each colored ink is reduced in a specific ratio with that reduced portion being replaced by the black ink. 
     This process makes it possible to reproduce a black whose density is greater than the black formed by superposing yellow, magenta and cyan, and the amounts of yellow, magenta and cyan inks used can thus be reduced. 
     However, if all the black portions are replaced by the black ink (100% UCR) as in the case of the above-described conventional apparatus, the quality of the image becomes degraded, so that it is impossible to realize 100% UCR. 
     Accordingly, an arrangement is made in which a small amount of each of the yellow, magenta and cyan is left. However, there is still a problem in that the remaining inks are scattered in the black character portions, and this scattering of the colored inks is noticeable, deteriorating the quality of the black characters. 
     A method of overcoming such problems is disclosed in U.S. Pat. No. 4,700,399 assigned to the assignee of this application. This application discloses a structure in which the proportion of undercolor removal carried out at the edge of a color image is increased and the quantity of the black ink is increased here to emphasize the edge. 
     SUMMARY OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide an image processing apparatus which is capable of performing efficient discrimination of character portions, thereby overcoming the above-described drawbacks of the prior art. 
     Another object of the present invention is to provide an image processing apparatus which is capable of preventing any downgrading of the quality of characters in a color image. 
     Still another object of the present invention is to provide an image processing apparatus which is capable of preventing the bleeding of characters in a color image to the peripheral portions thereof. 
     To these ends, according to one aspect of the present invention, there is provided a color image processing apparatus for digitally reading a color document and effecting digital printing, the color image processing apparatus comprising: character region extracting means for extracting a character region of said color document; black portion extracting means for extracting a black portion of said color document; and single black color processing means for processing a single black color only with respect to a region which falls within the character region and the black portion in the color document. 
     A further object of the present invention is to provide an image processing apparatus which is capable of detecting the continuation of a line in a character portion to favorably distinguish the character portion. 
     To this end, according to another aspect of the invention, there is provided an image processing apparatus comprising: input means for inputting image data; means for detecting an amount of change in the density of a block of m×n picture elements; two-valuing means for two-valuing the picture elements within the picture element block; and succession detecting means for detecting the succession of the two-valued picture elements within the picture element block. 
    
    
     These and other objects, features and advantages of the present invention will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram illustrating a first embodiment of the present invention; 
     FIG. 2 is a block diagram illustrating one example of a black detection circuit in the first embodiment; 
     FIG. 3 is a block diagram illustrating a first example of a character detection circuit in the first embodiment; 
     FIG. 4 is a diagram illustrating an example of a succession detecting circuit in the first embodiment; 
     FIG. 5 is a block diagram illustrating a second example of the character detection circuit in the first embodiment; 
     FIG. 6 is a diagram illustrating how selection is carried out in a UCR circuit in the first embodiment; 
     FIG. 7 is a diagram illustrating UCR processing in a half-tone portion and a character portion in the first embodiment; 
     FIG. 8 is a block diagram illustrating a second embodiment; 
     FIG. 9 is a block diagram illustrating the configuration of a black detection circuit  117  shown in FIG. 8; 
     FIG. 10 is a block diagram illustrating the configuration of a UCR circuit  114  shown in FIG. 8; 
     FIG. 11 are graphs illustrating the characteristics of a ROM  61  shown in FIG. 10; 
     FIG. 12 is a block diagram of a third embodiment of the present invention; 
     FIGS. 13A and 13B are diagrams illustrating a difference between a diagram and a reticular image. 
     FIG. 14 is a flowchart on discrimination of an image; 
     FIG. 15 is a block diagram of an image discrimination circuit in the third embodiment; 
     FIG. 16 is a diagram illustrating a specific arrangement of a correcter shown in FIG. 15; 
     FIGS. 17A and 17B are diagrams illustrating the relationships between information stored in a buffer group and an input image in FIG. 15; and 
     FIG. 18A is a block diagram of a white/black picture element succession detecting circuit; and 
     FIG. 18B is a diagram illustrating a specific configuration of the white/black picture element succession detecting circuit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a block diagram illustrating a first embodiment of the present invention. 
     An input sensor  10  has a photoelectric conversion element, such as a CCD camera or the like, and is adapted to read a document and output three-color separation signals of red (R), green (G) and blue (B). An A/D converter  11  converts each of the aforementioned signals into 8-bit digital signals, thereby making it possible to express gradations in 256 stages for each color. A log converter  12  converts into density the digital signals of each color expressed in gradations of 256 stages and outputs signals C 1 , M 1  and Y 1  which express the amounts of the three colored inks of cyan, magenta and yellow. 
     A masking circuit  13  effects color correction processing of the signals C 1 , M 1 , and Y 1 , and this color correction is carried out to eliminate a turbid component of the color-separation filter and a turbid component of the inks. In addition, the aforementioned masking is effected in accordance with the following formulae: 
     
       
         
           Y 
           2 
           =k 
           11 
           Y 
           1 
           +k 
           12 
           M 
           1 
           +k 
           13 
           C 
           1 
         
       
     
     
       
         
           M 
           2 
           =k 
           21 
           Y 
           1 
           +k 
           22 
           M 
           1 
           +k 
           23 
           C 
           1 
         
       
     
       C   2   =k   31   Y   1   +k   32   M   1   +k   33   C   1   
     where k 11  to k 33  are parameters that are determined experimentally. 
     A UCR circuit  14  performs undercolor removal processing and calculation of the black ink with respect to the signals C 2 , M 2 , and Y 2  output from the masking circuit  13 . This processing is effected in accordance with the following formulae: 
     
       
           Y   3   =Y   2 −α( K   2 −β) 
       
     
     
       
           M   3   =M   2 −α( K   2 −β) 
       
     
     
       
           C   3   =C   2 −α( K   2 −β) 
       
     
     where K 2 =min ( 2 , M 2  and C 2 ); K 2  an output of a black detection circuit; and α and β are constants. When α=1, and β=0, the state is called 100% UCR, in which case all the black formed by the three colors of yellow, magenta and cyan is replaced by the black ink. 
     A dither circuit  15  effects two-valuing of the signals C 3 , M 3 , Y 3  and K 3  output from the UCR  14 , and signals C 4 , M 4 , Y 4  and K 4  are sent to a color printer  16  one bit at a time, respectively. In other words, a color image is formed by the on/off operation of the ink dots. 
     A black detection circuit  17  detects a minimum value among the signals C 2 , M 2  and Y 2  output from the masking circuit  13  and outputs the same as the black signal K 2 . In addition, the black detection circuit  17  is arranged such that the output K 1  thereof is set to “1” when the amount of the black color is above a specific threshold. 
     In addition, a character detection circuit  18  detects the continuation of an image on the basis of the output M 1  of the log conversion circuit  12 . In other words, when there is succession in M 1 , the output R 1  is set to “1”. An AND circuit  19  performs an AND operation of the outputs K 2  and R 1 . Accordingly, when the color is detected to be black and its succession is detected, the output U 1  is set to “1”, and the amount of UCR is changed over by inputting this signal to the UCR circuit  14 . 
     FIG. 2 is a block diagram illustrating an example of the black detection circuit  17 . 
     Comparators  21   a ,  21   b  and  21   c  compare two of the color signals C 2 , M 2  and Y 2 , respectively, and the results of comparison are sent to a decision circuit  22 . The decision circuit  22  selects the minimum value of the three signals, and sends the result to a selector  23 , which in turn outputs the minimum value of the signals C 2 , M 2  and Y 2 . The signal of this minimum value is set as K 2 . A comparator  24  compares the minimum value signal K 2  with the threshold of M 2 , and when the minimum value signal K 2  is above that threshold, the comparator  24  sets the output K 1  to “1”. 
     FIG. 3 is a block diagram illustrating an example of the character detection circuit  18 . 
     An averaging circuit  30  operates an average value within a particular region, while a comparator  31  compares this average value with the original input signal M 1  and performs a two-valuing operation in such a manner as to output “1” when M 1  is greater and “0” when it is smaller. 
     A density detection circuit  32  determines the magnitude of the absolute value of a difference between the output M 1  and the average value, and outputs “1” when the absolute value is greater than a specific threshold and “0” when it is smaller. A correction circuit  33  is a gate circuit which allows the output of the comparator  31  to be passed only when the output of the density detection circuit  32  is “1” and constantly holds said output at “0” when the output of the density detection circuit  32  is “0”. As a result, the two-valuing operation is effected selectively only when the difference in density is large. This data is stored in a line buffer  34 . 
     FIG. 5 is a block diagram illustrating a second example of the character detection circuit in the above-described embodiment. 
     In this example, a succession detecting circuit  35   a  detects succession of picture elements calculated greater than the specific threshold and therefore represented by “1” of the two values in the vertical, horizontal and diagonal directions, i.e., four directions. An example of this succession detecting circuit  35   a  is illustrated in FIG.  4 . 
     In FIG. 4, picture element arrays  40 ,  41 ,  42 , and  43  indicate the positions of the picture elements in the horizontal, vertical, and two diagonal directions, respectively. The binary data of each picture element undergo logical operations by AND circuits  44   a ,  44   b ,  44   c    44   d , and each AND circuit outputs “1” when all of the five picture elements input are “1”. These outputs are subjected to a logical operation by an OR circuit  45 . Accordingly, when picture elements of “1” continue in any one of the vertical, horizontal and diagonal directions, the OR circuit  45  outputs “1”. This output “1” is a signal which indicates succession, and this signal is sent to the UCR circuit  14  as the signal R 1 . 
     In FIG. 5, a maximum value detector  50  and a minimum value detector  51  detect a maximum value and a minimum value, respectively, within a specific region (e.g., 3×3 picture elements). An averaging circuit  52  averages the maximum and minimum values thus obtained, and the average value is obtained by dividing by two a value in which the maximum and minimum values are added. A comparator  54  compares the aforementioned average value and the signal M 1  to output a binary signal. The comparator  54  outputs “1” when the signal M 1  is greater and “0” when it is smaller. 
     A subtracter  53  performs the operation of subtracting the minimum value from the maximum value, and output thereof is compared with a specific threshold in a comparator  55 , which outputs “1” when the output of the subtracter  53  is greater and “0” when it is smaller. A correction circuit  33   a  receives the outputs of the comparators  54 ,  55  and is similar to the correction circuit  33  shown in FIG.  3 . In addition, a line buffer  34   a  is similar to the line buffer  34  shown in FIG.  3 . 
     FIG. 6 is a block diagram illustrating selection by the UCR circuit  14  in the above-described embodiment. 
     UCR circuits  60   a ,  60   b ,  60   c  effect UCR processing of a half-tone portion, while UCR circuits  61   a ,  61   b  and  61   c  perform UCR processing of the character portion. 
     FIG. 7 is diagram explaining the UCR processing of a half-tone portion and the UCR processing of a character portion. 
     FIG.  7 ( 1 ) illustrates a state in which the color signal data Y 2 , M 2 , C 2 , K 2  are input at the same level. FIG.  7 ( 2 ) is a diagram which shows the result of UCR processing of the half-tone portion, in which the amounts of the color signal data Y 2 , M 2 , C 2  are reduced to approximately half and are set as Y 3 , M 3 , C 3 , and, instead, the black data K 3  is produced in a black producing circuit  62 . This is referred to as 50% UCR. 
     Meanwhile, in a character portion, as shown in FIG.  7 ( 3 ), the amounts of the color signal data Y 3 , M 3 , C 3  are set to substantially zero, and, instead, the black data K 3  is produced in the black producing circuit  63  so as to replace the colored inks. This is referred to as 100% UCR. 
     By changing over select circuits  64   a ,  64   b ,  64   c ,  64   d  in accordance with the select signal U 1 , the afore-mentioned data are selected to output the amounts of ink C 3 , M 3 , Y 3 , K 3  that are suited to the half-tone portion and the character portion. 
     In the above-described embodiment, 100% UCR is performed with respect to portions that are detected to be character portions, but a description will now be given of a second embodiment which is capable of reproducing the character portion more satisfactorily by varying the percent of UCR in correspondence with the levels of the black signals in a region which is detected to be such a character portion. 
     FIG. 8 is a block diagram illustrating the configuration of such an embodiment, and those elements that have functions similar to those shown in FIG. 1 are denoted by the same reference numerals, and a description thereof will be omitted. 
     In FIG. 8, a black detection circuit  117  detects a minimum value of signals C1, M1, Y1 on the basis of the signals C1, M1, Y1, and the output of this black detection circuit is set as the black signal K2. A black level Bl is determined in correspondence with the value of this black signal K2. The black level Bl is set to, for instance, four stages, as shown in Table 1 below. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 K2 
                 Bl 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0 ≦ K2 &lt; KT1 
                 0 
               
               
                   
                 KT1 ≦ K2 &lt; KT2 
                 1 
               
               
                   
                 KT2 ≦ K2 &lt; KT3 
                 2 
               
               
                   
                 KT3 ≦ K2 &lt; 255 
                 3 
               
               
                   
                   
               
             
          
         
       
     
     Incidentally, KT1, KT2 and KT3 are constants that are respectively determined experimentally. 
     A UCR amount decision circuit  119  decides a UCR amount on the basis of the output R 1  and the black level Bl. The relationships among the output R 1  of the character detecting circuit  18 , the black level Bl, the output signal U 1  of the UCR amount decision circuit  119 , and the UCR amount are shown in Table 2 below. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 R1 
                 Bl 
                 U1 
                 UCR Amount 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 0 
                 0 
                 0% UCR 
               
               
                 1 
                 1 
                 1 
                 25% UCR 
               
               
                 1 
                 2 
                 2 
                 50% UCR 
               
               
                 1 
                 3 
                 3 
                 100% UCR 
               
               
                 0 
                 . . . 
                 0 
                 . . . 
               
               
                   
               
             
          
         
       
     
     A UCR circuit  114  changes over the UCR amount in correspondence with the output signal U 1  of the UCR amount decision circuit  119 . 
     FIG. 9 is a block diagram illustrating a specific example of a black detection circuit  117 . 
     In FIG. 9, those elements having functions that are similar to those shown in FIG. 2 are denoted by the same reference numerals, and a description thereof will be omitted. 
     In FIG. 9, the function of a comparator  124  differs. Namely, the comparator  124  compares the black signal K2 and a plurality of specific thresholds KT 1 , KT 2 , KT 3 , and outputs various black levels Bl, as shown in Table 1. 
     A description will now be given of the configuration of the UCR circuit  114  shown in FIG.  8 . 
     FIG. 10 is a block diagram illustrating a specific example of the UCR circuit  114  in accordance with the second embodiment. 
     A table ROM  61  determines output data with respect to input data in accordance with the value of U 1  output by the UCR amount decision circuit  119 , and when U 1  is 0, 1, 2, and 3, the gradients in FIG.  11 ( 1 ) are 0.1, ¼, ½, and 1. The signal K3 output by this table ROM  61  is the black data showing the amount of black, and the subtracters  60   a  to  60   c  subtract the black data K3 from C2, M2, Y2, respectively, to output the signals C3, M3, Y3. 
     In addition, the quality of the image can be improved further if the amount of black and the UCR amount are varied smoothly, as shown in FIG.  11 ( 2 ). 
     In accordance with this embodiment, by changing over the UCR amount in correspondence with the selected signal U 1 , it is possible to determine the optimum ink amounts C3, M3, Y3, K3 for the half-tone portion and the character portion. 
     In the above-described embodiment, although magenta signal (M1) is used in detecting the character, a green signal or a signal representing another level of brightness may be used instead. 
     In addition, in accordance with this embodiment, when a character region is to be extracted, since the character region is extracted by taking note of the continuity of the line forming the character, it is possible to accurately extract the character portion unlike in the case where the edge is merely discriminated to detect the character region. Accordingly, when processing a color image in which each of the Y, M, C colors is formed by half-tone dots, it is possible to overcome the drawback that if the half-tone dots are superposed, the superposed half-tone dots are erroneously judged to be a character region although they do not actually constitute a character region. 
     As has been described above, in the above-described embodiments, the character portion is extracted by the character detecting circuit  18  whose details are shown in FIG. 4. A description will now be given of a third embodiment which is capable of further improving the accuracy of this character detection circuit and of effecting processing in accordance with different types of input images. 
     FIG. 12 illustrates an outline of the structure of an image forming apparatus according to another embodiment of the present invention. 
     Referring to the figure, reference numeral  101  represents an input scanner for optically reading an original, the input scanner being constituted by, for example, CCDs. Reference numeral  102  represents an A/D converter for converting a voltage level signal  201  from the input sensor  101  to digital data  202  of, for example, 8 bits (256 gradients). Reference numeral  103  represents a tone correcting circuit for correcting the converted digital data  202  in accordance with the characteristics of the input sensor  201  or those of a printing mechanism, the tone correcting circuit  103  being constituted by, for example, a look-up table. The digital data  202  which has been corrected is output to a picture identification circuit  107 , and also to a simple two-valuing circuit  104 , a dither circuit  105 , and a moire suppressed two-valuing circuit  106 . 
     In the simple two-valuing circuit  104 , by comparing the input digital data  202  with a predetermined threshold (for example, “128”, which is half of the maximum gradient), data  204  for controlling on and off (“1” or “0”) of an output image is output. The dither circuit  105  outputs the results of comparing a predetermined dither matrix therein (each matrix element is provided with a threshold) with the input digital data  202 , the results being output as data  205 . The moire suppressed two-valuing circuit  106  is arranged, in this embodiment, to perform the two-valuing treatment by way of preparing a plurality of dither matrices which cannot easily generate beat with the number of line of half-tone dots and selecting the plurality of dither matrices through successive changes. However, a smoothing treatment in which the half-tone dot frequency is cut may be performed. Reference numeral  108  represents a switch for selecting from the circuits  104  to  106 , based on the control data from the picture identification circuit  107 , one of the outputs from among outputs  204  to  206 . The data selected is output to a printer  109 . 
     The picture identification circuit  107  outputs data to a control signal  207  when it is detected that the subject picture element is an edge of a character or a diagram, the data representing a command to select the output from the simple two-valuing circuit  104 . The picture identification circuit  107  outputs data representing a command to select the output from the dither circuit  105  to the control signal  207  when it is decided that the subject picture element is a part of a photographic picture. The picture identification circuit  107  outputs data representing a command to select the output from the moire suppressed two-valuing circuit  106  to the control signal  207  when it is decided that the subject picture element is a half-tone dot picture element. Each circuit  104  to  106  is provided with a buffer or the like for the purpose of synchronization with the output signal  207  from the picture identification circuit  107 . 
     &lt;Description of the Principle of Picture Identification (FIG.  13 )&gt; 
     In this embodiment, similar to the above-described embodiment, means for deciding the states of the subject picture element is employed in which the states of the subject picture element are identified from the relationship between the subject picture element and the picture elements surrounding it. Specifically, a central picture element consisting of a 3×3 picture element block is arranged to be the subject picture element, and the state of the subject picture element is decided in accordance with the difference in the averaged concentration between the subject picture element and the eight neighbouring picture elements. If it is decided that the difference in the averaged concentration between the subject picture element and the neighboring picture elements is not significant, it is decided that the subject picture element is a part of a photographic picture. 
     The problem is to decide whether the subject picture element is a part of a character or a diagram, or whether it is a half-tone dot. 
     FIGS. 13A and 13B respectively illustrate a part of character (diagram) and a part of a half-tone dot (the hatched area is in black). As shown in the figures, it is decided that the subject picture element is a character or a diagram when the black areas are continuous right through the white base, while it is decided that the subject picture element is a part of a reticulation in other cases. 
     The flow-chart shown in FIG. 14 illustrates the process of reaching this decision. First, in step S 30 , it is determined whether the subject picture element is an edge. If no edge is detected, the flow advances to step S 31  in which it is determined that the subject picture element is a part of a photographic picture, whereupon the output from the dither circuit  105  is selected. On the other hand, when an edge is detected, the subject picture element is two-valued in step S 32  If it is determined that the two-valued data has a succession (step S 23 ), it is decided, in step S 34 , that the subject picture element is a character or a diagram, whereupon the output from the simple two-valuing circuit  4  is selected. If no succession in detected, it is determined, in step S 35 , that the subject picture element is a half-tone dot picture, whereupon the output from the moire suppression two-valuing circuit  106  is selected. 
     &lt;Description of Picture Identification Circuit (FIGS. 15 to  18 )&gt; 
     The specific structure of the picture identification circuit  107  for performing the above-described treatment is shown in FIG. 15, and an outline of this treatment will now be described. 
     The circuit shown in FIG. 15 is a circuit resulting from modification of the circuit shown in FIG. 5, Data  203  output by a tone correction circuit  103  is first input to an averaged concentration calculator  170  (equipped with buffers of three lines) in which the averaged concentration D of the eight picture elements (a block of 3×3 picture elements) surrounding the subject picture element is calculated. This is the difference between this embodiment and the averaging process illustrated in FIG.  5 . The thus-calculated averaged concentration is output to each input terminal of a comparator  171  and a subtracter  172 . The comparator  171  compares the calculated averaged concentration D with the concentration Di of the subject picture element. When it is decided that Di&gt;D, the comparator  171  outputs, as the output B thereof, “1”, while when it is decided that this is not the case (Di≦D), it outputs “0”. 
     The subtracter  172  calculates the difference between the averaged concentration D and the concentration Di of the subject picture element. In this case, the degree ΔD of difference ΔD, that is, ΔD=|D−Di| is calculated (wherein | . . . | is an absolute value). The comparator  171  and the subtracter  172  are each provided with a latch for retaining the concentration of the subject picture element, whereby the averaged concentration D output by the averaged concentration calculator  170  can be used in the calculation in a synchronized manner. 
     The output ΔD from the subtracter  172  is output to a comparator  173  wherein the output ΔD is compared with a predetermined threshold T. The result (signal E) of this comparison is output to a decision circuit  179  through a correction circuit  174  and a delay circuit  180  which will be described later. When ΔD&gt;T, a signal of a level “1” is output as a signal E, while when ΔD≦T, a signal of a level “0” is output as the signal E. 
     The correction circuit  174  (see FIG. 5) receives a signal B and the signal E, and then it outputs signals B 1  and B 2  to line-buffer groups  175   a  and  175   b  (for example, FIFO) covering five lines whereby the signals B 1  and B 2  are temporarily stored. Both these signals B 1  and B 2  become “0” when the signal E is “0”. When the signal E is “1” and the signal B is “0”, the signal B 1  becomes “1” and the signal B 2  becomes “0”. Conversely, when the signal B is “1”, the signal B 1  becomes “0” and the signal B 2  becomes “1”. 
     The relationships of these signals is shown in Table 3. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 E 
                 B 
                 B 1   
                 B 2   
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                 1 
                 0 
                 0 
               
               
                   
                 1 
                 0 
                 1 
                 0 
               
               
                   
                   
                 1 
                 0 
                 1 
               
               
                   
                   
               
             
          
         
       
     
     As shown in this table, when it is determined that there is no significant difference between the concentration Di of the subject picture element and that of the neighbouring picture elements (that is, when E=0, it is determined that there is no significant difference in concentration), both outputs B 1  and B 2  from the correction circuit  174  become signals of a “0” level, and are stored in corresponding line-buffer groups  75   a  and  75   b.    
     When the concentration Di of the subject picture element is significantly lower than that of the neighboring picture elements, a 1-bit signal is stored in the corresponding line-buffer groups  175   a  and  175   b , the 1-bit signals being so constituted that the output B 1  is set to “1” and the output B 2  is set to “0”. On the other hand, when the concentration Di of the subject picture element is significantly higher than the neighboring picture elements, a 1-bit signal is stored in the corresponding line-buffer groups  175   a  and  175   b , the 1-bit signal being so constituted that the output B 1  is set to “0” and the output B 2  is set to “1”. 
     Next, a specific state of storing data in the line-buffer groups  175   a  and  175   b  with respect to the input image will be described with reference to FIGS. 17A and 17B. 
     In FIG. 17A, when, for example, an input picture  600  (which shows a part of a character or a diagram) is input by the procedure described above, the data illustrated in this figure is stored in the line-buffer groups  175   a  and  175   b . When an input picture  601  (which is equivalent to a half-tone dot picture) is input, the data shown in FIG. 17B is stored in the corresponding line-buffer groups  175   a  and  175   b . That is, in the line-buffer group  175   a , black edge portions are located in the white base, the black edge portions being located in the form of a “1”. In the line-buffer group  175   b , white edge portions are located in the black base, the white edge portions being located in the form of a “1”. In these figures, reference numerals  602  to  605  each represent a location of the subject picture element. 
     As described above, when the outputs B 1  and B 2  covering five lines are located in the corresponding line-buffer groups  175   a  and  175   b , a white succession detecting circuit  176  and a black succession detecting circuit  177  respectively determine whether the black or white edges of the subject picture element are successive. 
     Since the structure of the white succession detection circuit  176  is the same as that of the black succession detection circuit  177 , the black succession detection circuit  177  alone will now be described. 
     The black succession detection circuit  177  comprises, as shown in FIG. 18A, detectors  160  and  163  for detecting successions in each direction. When a detector detects a succession in the relevant direction, its output becomes “1”. The result of the detection is output to a logical add circuit  164  in which the result is output as an RB signal. 
     Specifically, the black succession detection circuit  177  comprises, as shown in FIG. 18B, a horizontal succession detector  160  which consists of a latch  160   a  and an AND gate  160   b.    
     Therefore, the RB signal becomes “1” only when “1” is successively retained in either one of the latched in the horizontal, vertical, left hand or right hand directions, including the result (signal B 2 ) of detecting the edges of subject picture elements. In the other words, if each latch  160   a  to  163   a  includes a “0”, the RB signal becomes “0”. 
     Referring back to FIG. 15, outputs RW and RB from the corresponding white succession detection circuit  176  and the black succession detection circuit  177  are logic-added by the logical add circuit  178  thereby to supply an output R to a decision circuit  179 . The output E from the comparator  173  is output to another input terminal of the decision circuit  179  through a delay circuit  180  in synchronization with the detection of the succession of subject picture elements. 
     The decision circuit  179  forms an output signal  207  shown in Table 4, the output signal  207  being formed from the signal R and the signal E. 
     As can be clearly seen from the above description, the case of E being 0 corresponds to a state in which contrast is relatively weak, the case of E being 1 corresponds to a state in which contrast is relatively strong, the case of R being 1 corresponds to a state in which there is a succession, and the case of R being 0 corresponds to a state in which there is no succession. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 E 
                 R 
                 Output H 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 0 
                 0 
               
               
                   
                 1 
                 0 
               
               
                 1 
                 0 
                 1 
               
               
                   
                 1 
                 2 
               
               
                   
               
             
          
         
       
     
     Therefore, the switch  108  shown in FIG. 12 selects the simple two-valuing circuit  104  when the output signal H from the decision circuit  179  is “1”, thereby deciding the character region. The switch  108  selects the dither circuit  105  when the output signal H is “0”, thereby it decides that it is a half-tone picture, and it selects a moire two-valuing circuit  106  when the output signal H is “2”, thereby deciding that it is a half-tone dot picture. Thus a suitable treatment system can be selected to accord with the types of input pictures. Consequently, a good picture can be formed. 
     As an alternative to the output from the character detection circuit  18  shown in FIG. 1 or the output from the character detection circuit  118  shown in FIG. 8, the output signal H obtained from the picture identification circuit  107  may be input to the AND circuit  19  or the UCR amount decision circuit  119 . In this way, the state of the character region can be detected even more precisely. 
     In the case where the output signal H is employed as an alternative to the output from the character detection circuit  18 , a circuit may be provided in such a manner that when H is “1”, 100%—UCR is conducted, while in the other cases, that is, where H is “0” or “2”, 100%—UCR is not conducted. 
     In the case where the output signal H is used as an alternative to the output from the character detection circuit  118 , 100%—UCR may be conducted when “H” is “1”, while, for example, no 100%—UCR is conducted when H is either “0” or “2”. 
     Although in the picture identification circuit  107  in the embodiments described above it is determined that there are edges when the difference in the density between the subject picture element and the neighboring picture elements exceeds a certain degree, this invention is not limited to this embodiment. Another type of circuit, for example, a circuit formed by the blocks  50  to  55  and the correction circuit  33   a  shown in FIG. 5 may, of course, be used too. 
     As described above, according to the decision system conducted in accordance with the embodiments, if a picture is input in which half-tone, characters, diagrams and half-tone dots are disposed in a mixed manner, each picture can be distinguished. 
     Furthermore, in the color image processing apparatus according to the embodiment, since high UCR % is applied to the black character region, black characters and other half-tone color pictures can be reproduced with high quality resolution. 
     As described above, when the undercolor treatment is applied to color pictures, in a method in which a stronger undercolor treatment is applied to the edge portions of a color picture, that is, when a high UCR % is employed, the picture becomes too hard because the half-tone color picture formed by half-tone dots is subjected to an excessive high UCR %. However, according to the system shown in the embodiment, since the half-tone dots and the characters are distinguished, the above phenomenon can be prevented, whereby a high-quality picture can be obtained. 
     Furthermore, although the quantity of ink is controlled and the UCR % is changed for the purpose of controlling the undercolor treatment in these embodiments, this invention is not limited to cases in which the above two processes are conducted. Either one may, of course, be conducted alone. 
     Furthermore, although in these embodiments the color dissolving treatment and the undercolor treatment are conducted in an electronic manner, these treatments are not limited to those conducted in an electronic manner, and they may of course conducted in an optical manner, similar to the case of a treatment conducted by a process machine.