Image data processing method for selective partial image display

A retrieved image display method in an image file system in which image data records undergone a data compression and index records including positional information of the image data records are stored in a file medium. The method includes a first step to specify a partial region of a retrieved image to be displayed on a display screen, a second step to attain, based on positional information above included in an index record corresponding to the retrieved image, a recording position of an image date portion on the file medium corresponding to the partial region to be displayed and to partially read out image data from the image data record, and a third step to restore the compressed image data thus read out into the original image data and to display the restored image data on the display screen. In accordance with to the partial region specified in the first step, the operations of the second step and the third step are successively and repetitiously achieved for a plurality of retrieved images to thereby flip pages of the retrieved images on the display screen.

CROSS-REFERENCES TO THE RELATED APPLICATIONS 
This application relates to a U.S. application Ser. No. 067,014, filed June 
29, 1987 now abandoned by Haruo TAKEDA and Kuniaki TABATA, entitled "IMAGE 
DATA DISPLAY SYSTEM" and assigned to the present assignee, based on 
Japanese Patent Application No. 61-149510 filed June 27, 1986. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image file system, and in particular, 
to a method for storing and displaying image data suitable for displaying 
at a high speed a retrieved image in an image file system. 
2. Description of the Related Art 
Recently, a document image file system (electronic file) using a 
large-capacity optical disk has become noticeable as a new means for 
document management. An optical disk has a large data storage capacity to 
record a great amount of data including the image data and therefore can 
be used as a store means storing document image information such as an 
account sheet, a design drawing, a contract, and the like. When retrieving 
these document images, it is desirable in ordinary cases to use an index 
such as a predetermined document name, classification name, keyword, or 
the like. When the index becomes to be complicated, however, it takes time 
to effect a job storing the document images together with the complex 
indices; furthermore, such a complicated index often becomes difficult to 
remember when a document is to be retrieved. To overcome this difficulty, 
only a simple index such as a classification name is often added to the 
document image for the storage in practice. Moreover, a stored image 
having a complex index added thereto is commonly retrieved by specifying 
only a simple index. In this case, to retrieve an objective document 
image, the operator must sequentially display on a display screen a 
plurality of candidate data retrieved by specifying an index such as a 
classification name so as to visually confirm the display contents, 
thereby extracting the objective document. 
As a method for selecting the document image above, there has been a 
method, for example, described in pages 6-7 of the "Operation manual for 
Hitachi Optical Disk File System" (manual number 60-10-001-20) in which a 
previous page key or a next page key is used. According to this method, a 
sheet of image data is displayed on the screen each time the key is 
pressed. This method may be improved, for example, such that when a page 
change key is pressed, an automatic page change is effected for the 
retrieval data so as to sequentially display the data on the display 
screen until the next key depression is recognized as a termination 
command. 
As described above, in the case where the document images obtained by the 
index retrieval (primary retrieval) are sequentially displayed so as to 
visually extract an object document therefrom (secondary retrieval), it is 
desired to increase the speed of the page change in a range in which the 
operator can judge whether the display document is an objective document 
or not, thereby minimizing a period of time required for the secondary 
retrieval. In the conventional retrieval system, however, the processing 
is achieved in a form that the document data attained by the primary 
retrieval is read from the document image file in a page-by-page (i.e. 
record-by-record) fashion so as to sequentially display the record data 
and the read speed of each image data is restricted by the performance of 
the file device; consequently, the cycle of the update of display content 
cannot be less than the time required to read data for a document, which 
leads to a problem that a wait time takes place to obtain the next screen. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a method and 
system for displaying a retrieved image which can sequentially display a 
plurality of retrieved images at a high speed. 
Another object of the present invention is to provide a method for storing 
or registering compressed image data suitable for a high-speed display of 
a retrieved image. 
In a document retrieval in which document images attained by the index 
retrieval are sequentially displayed to enable the operator to visually 
retrieve an objective document, the entire image of each document need not 
be necessarily displayed, for example, only a portion of the document such 
as a title, a name of an author, or a synopsis may suffice the retrieval 
object in many cases. For example, in the case where the operator bears in 
mind a location of description identifying an objective document, the 
necessity/ unnecessity of the displayed document is judged by the operator 
depending on the location; consequently, the function to display the 
primary retrieval data need only display a particular partial region 
specified by the operator. 
To achieve these objects, according to the method for displaying the 
retrieved image according to the present invention, there are included in 
an image file system storing on a file medium a plurality of image data 
records each including compressed data and at least one index record 
including positional information of the image data record, a first step of 
specifying by the operator a partial region of a retrieved image to be 
displayed on a display screen, a second step of selectively reading, based 
on the positional information contained in the index record corresponding 
to the retrieved image, a particular image data region corresponding to 
the partial region to be described from each retrieval image data record 
on the file medium, and a third step of restoring the compressed image 
data thus read to display the restored image data on the display screen. 
When there exist a plurality of retrieved images to be displayed, the 
operations of the second step and the third step are repeatedly 
accomplished depending on a result of the designation of the partial 
region in the first step. 
In a file system of image data, since a plurality of images are stored on a 
file medium for an effective use of a memory area, original images are 
encoded to obtain compressed data for storage in a common practice. In 
this case, a density of information in a record on the file medium 
undergone the data compression is different from a density of information 
in the original image. As a consequence, for example, even if information 
equivalent to half a record is read from the record, the obtained 
information data does not necessarily restore the complete portion 
equivalent to half the page of the original image. According to the 
present invention, based on positional information contained in an index 
record, a recording position of an image data on the file medium 
corresponding to a position in an original image specified by the user for 
a display or to a partial area of a reproduced image is obtained so as to 
selectively read out only a data portion at a position corresponding to 
the partial region from each image record on the file medium, which 
minimizes the quantity of image data to be read and hence reduces the 
image display cycle. In the first embodiment according to the present 
invention, for example, to correspond the partial region in the original 
image specified by the user to a position of the particular region of the 
compressed image data to be read from the file medium, the original image 
is subdivided into a plurality of subregions in advance and the recording 
position of the compressed data associated with each subregion is stored 
in an index record when the image data is registered to a file. For a 
display position, the user specifies at least one subregion of the 
subdivided original image. Furthermore, in the case where the original 
image is directly registered, namely, without subdividing the original 
image, when a display subregion is specified by the user, based on the 
positional information contained in the index record, each compressed 
image record is subdivided into a plurality of partial data areas or the 
like; moreover, assuming that there exists a proportional relationship 
between the data distribution in the compressed image record and that in 
the reproduced image, a partial data region corresponding to the display 
subregion specified by the user is extracted. Since the reproduced 
(restored) image of the partial data area thus attained may possibly be 
shifted from the subregion requested by the user, in the embodiment of the 
present invention, a read region for the image data read operation is set 
to be greater than the partial data region obtained by the subdivision of 
the image. 
According to another embodiment of the present invention, a subregion to be 
displayed is identified by a specification of a time interval desired by 
the operator to change over between the respective images on the display 
screen. That is, when the operator specifies a time interval, a volume of 
compressed image data which can be displayed in the interval of time is 
read from each retrieved image data. In this case, if a data is to be read 
beginning from each image record, the quantity of the read data increases 
as the specified time interval becomes longer, namely, the document image 
display is effected with an increasing number of character lines 
displayed. 
The foregoing and other objects, advantages, manner of operation and novel 
features of the present invention will be understood from the following 
detailed description when read in connection with the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is an overall configuration diagram of an image file system 
according to the present invention including a scanner 1 for inputting 
image data, a controller 2 of the scanner 1, an image file 3A for storing 
the registered data in the form of compressed, encoded data, an index file 
3B for storing index data prepared to retrieve the corresponding image 
data, a controller 4 for effecting a data read operation and a data write 
operation on the image file 3A and the index file 3B, a display 5 for 
displaying image data and character data such as a command, a controller 6 
for controlling the display 5, a keyboard 7 for inputting character data 
such as a command and index data, a processor (CPU) 8 for controlling the 
entire system, a memory 9 for storing programs to be executed by the CPU 
8, a work memory 10 for storing various variables or tables to be used by 
the CPU 8, buffer memories 11A-11B for temporarily storing an encoded 
image read from the image file 3A, an image memory 13 for storing original 
image data inputted from the scanner 1, a processor 14 dedicated to encode 
or compress original image data, a processor 15 dedicated to decode or 
expand the encoded image data, a bit map memory 16 corresponding to the 
display contents of a displayed image, and a bus 17. 
In this configuration, the memories 9-13 and 16 need not be physically 
separated devices and may be allocated as the different store area in the 
same memory device. Furthermore, as will be described later, some of these 
memory areas may be commonly used for the purposes to reduce the total 
memory. Although the image file 3A and the index file 3B may be cofigured 
by means of separate file media, since the image file 3A and the index 
file 3B are to be constructed in pair in this configuration, different 
regions of the optical disk 3 are allocated as the image file 3A and the 
index file 3B, respectively. Consequently, the file controller 4 is shared 
among the image file 3A and the index file 3B. Incidentally, the file 
controller 4 is assumed to include a driving device of the optical disk 3. 
Furthermore, although the encode processor 14 and the decode processor 15 
are different from each other in a sense of the circuit, the encode 
processor 14 and the decode processor 15 are often integrated in the same 
LSI chip and hence are located to be adjacent to each other in this 
schematic diagram. Various encoding algorithms have been known for the 
image data to be encoded by the encode processor 14, for example, a 
run-length encode method described in a literature entitled "Image Signal 
Processing for FAX and OA" by Takehiko FUKINUKE published by Nikkan Kogyo 
Newspaper (1982), pp. 61-75. However, the gist of the present invention is 
not changed by the encode algorithm, namely, any other algorithm may be 
used. 
FIG. 2 is a schematic diagram showing the image file region 3A and the 
index file region 3B on the optical disk 3. There is formed on the optical 
disk 3 a spiral track TR continuing from a center side to an outer side of 
the disk 3. The track TR is subdivided into a plurality of tracks TR-0 to 
TR-m+n with reference to the reference line L in which the track numbers 
are assigned as 0 to m+n beginning from the pertinent inner track. 
Furthermore, each track is subdivided into a plurality of sectors SE-0 to 
SE-p each being the minimum unit of the data block for the read and write 
operations. The respective sectors are designated with sector numbers 0-p 
in the passing order of a read/write head thereover when the optical disk 
3 rotates in a direction R. According to the present embodiment, a region 
from sector 0 of track 0 (TR-0) to the last sector of track m (TR-m) is 
allocated as the index file region 3B for storing indices including code 
data, whereas a region from sector 0 of track m+1 (TR-m+1) to the last 
sector of track M=N (TR-m+n) is used as the image file region B to store 
document image data. Although the address of each sector can be uniquely 
determined by use of a track number and a sector number, in this 
embodiment, the sector numbers are sequentially assigned beginning from 
sector 0 of the track 0, for example, sector j of track i is defined as 
[i.(p+1)+j]-th sector. 
FIG. 3 shows corresponding relationships between original image data 20 
stored in the image memory 13 and image data (records) 30 which are 
compressed through the encoding operation so as to be stored in the buffer 
memory 11A. In this example, since P=4, the original image data 20 is 
subdivided into four square classification areas 21-24 of the same size. 
Since the respective subregions 21-24 in the original image include 
different amounts of information, respectively, if the image data is 
encoded for each subregion, the subregions 31-34 in the encoded image data 
30 become to be of different sizes, respectively according to the data 
amounts thereof. In FIG. 3, B(i) indicates the data size of an i-th 
partial region of the encoded image. Although the data size can be 
conveniently represented by use of the number of bytes and the number of 
bits of a terminal byte, the total bit count is used in this embodiment 
for convenience of explanation. In addition, A(i) over the encoded image 
30 indicates the head address of the i-th subregion. Although, in 
practice, this address can be conveniently expressed by use of a sector 
number in the image file region 3A above, a byte position, and a terminal 
bit position in the sector; a sector number A'(i) and a bit position a(i) 
in the sector are employed for convenience of the subsequent description 
of this embodiment. 
In this embodiment, as described above, the original image data 20 is 
subdivided into a plurality of partial regions and each partial region is 
encoded so as to specify a partial region 2i in the original image. In 
this situation, in order to identify the partial region 3i of the encoded 
image corresponding to the partial region 2i, a boundary position of each 
encoded partial region 3i comprising the head address A(i) and the data 
size B(i) in this example is before-hand stored in the index file 3B. An 
index record 40 to be recorded in the index file 3B is here configured, 
for example, as shown in FIG. 4, which comprises an index field 41, fields 
42-i and 43-i for storing the sector number A'(i) and the bit position 
a(i) in the sector indicating a location where the i-th partial region is 
stored in the image file 3B, and a field 44i for recording the length B(i) 
of the encoded data of the i-th region. The head address of the i-th 
partial region in the image file 3B is identified by use of A'(i) and 
a(i). 
With the index file constituted in this form, in the case where image data 
attained by the index retrieval are sequentially outputted to the display 
5, when the operator effects, for example, a display specification for 
only the upper-half of each image data, only the encoded image regions 
31-32 respectively associated with the partial regions 21-22 corresponding 
to the upper-half of the original image can be selectively read out from 
the image file 3A. Since the selective data read operation enables to 
minimize the period of time required to achieve a read operation of each 
image data from the image file 3A, the update cycle of the display 
contents on the display 5 can be considerably reduced. 
Referring next to the flowcharts of FIGS. 5A-5D, description will be given 
of the generation of the image file 3A and the index file 3B and the 
control operation of the image filing system to display the retrieved 
image data at a high speed by use of the image file 3A and the index file 
3B. A program associated with the flowcharts is stored in the memory 9 so 
as to be executed by the CPU 8. In step 102, the optical disk 3 is first 
installed in the file controller 4. In step 104, the optical disk 3 is 
then searched to attain an address (an index file pointer P.sub.b) on the 
optical disk at which the next index record is stored and an address (an 
image file pointer P.sub.a) on the optical disk at which the next image 
data is stored. The obtained index file pointer P.sub.b and image file 
pointer P.sub.a are stored in the work memory 10. 
In step 106, an input command entered by the operator is judged. If the 
input command is a register command, step 108 is executed to write the 
input image data from the scanner 1 in the image memory. In the next step 
110, the image data is transferred to the bit map memory 16 so as to be 
displayed on the display screen. Judging the quality of the image 
displayed on the display 5 such as an inclination, a position, and a 
gradation thereof, the operator inputs the result of the judgment (step 
112). If the input image is not attended by any problem, step 114 is 
effected to input from the keyboard 7 such index data as a document name 
and a classification name to be used as a retrieval key of the image data 
above. The index data items are stored in the work memory 10. In this 
embodiment, it is assumed to input only character strings indicating 
classification names of the document such as "TOKKYO (patent)", "RONBUN 
(thesis)", and "HOKOKUSYO (report)". Subsequently, in step 116, the 
divisor P used to subdivide the original image as described above is 
indicated through a command input from the keyboard 7. The divisor P may 
also be prescribed to be treated as a value beforehand fixed on the system 
side. In such a case, the input operation in the step 116 can be dispensed 
with. 
In steps 118-126, the original image data 20 stored in the image memory 13 
is divided by the divisor P to attain a plurality of partial regions, 
encoded image data is stored in the buffer memory 11A, and an index record 
described in conjunction with FIG. 4 is generated in the work memory 10. 
In this sequence, first of all, the value of a division area indication 
parameter i is initialized to one (i=1) in the step 118 and then the value 
of the image file pointer P.sub.a attained in the step 104 is set to A(i). 
At this point, the pointer P.sub.a indicates the first bit position of the 
identified sector and a(1)=1. In step 120, the i-th partial region 2i of 
the original image is subjected to the encode processing, which is 
executed by the encode processor 14 and then the encoded image data region 
3i is written in the buffer memory 11A beginning from a position 
immediately following the (i-1)-th partial region (the first partial 
region 31 is written in the buffer memory 11A beginning from the top 
thereof). In step 122, the size B(i) and the address A(i) of the partial 
region 3i of the encoded image are added to an index record in the work 
memory 10. In step 124, the store address A(i+1) of the next (i+1)-th 
partial region 3i+1 is calculated from 
EQU A(i+1)=A(i)+B(i). 
When A(i+1) is represented by a sector address A'(i+1) and a bit position a 
(i+1), the address can be obtained from 
##EQU1## 
EQU a(i+1)=(A(i)+B(i))mod K 
where, the symbol [] indicates a Gaussian symbol meaning that an integer is 
obtained by truncating the content thereof, K is the number of bits per 
sector, and "mod" denotes a remainder of the division. 
In step 126, the value of the parameter i is incremented by one and then 
the steps 120-126 are repeatedly achieved until the value of i exceeds the 
divisor P, thereby obtaining the encoded image 30 of FIG. 3 and the index 
record of FIG. 4 in the buffer memory 11A and the work memory 10, 
respectively. 
In the case where the data code capacity per sector of the optical disk 3 
is 100 bytes, namely, K=800 (bits) and the sector address indicated by the 
file pointer P.sub.a is "50", if the sizes of the respective encoded 
partial regions B(1)-B(4) are "1200", "4800", "2400", and "2400", the 
index record is provided with the partial region addresses A(1)-A(4) as 
shown in FIG. 4. 
The encoded image data 30 stored in the buffer memory 11A is stored, in 
step 128, in a region including a plurality of sectors of the disk 
beginning from the address A(1) of the image file region 3A, whereas the 
index record 40 generated in the work memory 10 is recorded, in step 130, 
in a sector at an address position indicated by the index file pointer 
P.sub.a of the index file region 3B on the optical disk. In step 132, for 
a preparation of the registration processing of the next image data, the 
values of the image file pointer P.sub.a and the index file pointer 
P.sub.b are respectively updated to the values indicating the next 
recording start sector. In step 134, the program judges whether or not an 
end command has been received. If an end command has been inputted, 
control is returned to the step 106; otherwise, the step 108 is achieved 
to effect the input processing of the next image. 
Next, a description will be given of a control operation applied to the 
case where the operator inputs a command specifying an image retrieval. 
FIG. 6 is a schematic diagram illustrating a retrieval function in the file 
system according to the present invention in which reference numerals 20, 
20', and 20" represent image data respectively retrieved. The shaded 
portions in FIG. 6 indicate the portions to be displayed on the screen. In 
FIG. 6, (A) stands for a state in which the entire screen is displayed, 
(B) represents a state in which the upper-half portion (the first and 
second partial regions) of the image is displayed, (C) is a state in which 
upper quarter portion (the first partial region) of the image is 
displayed, (D) expresses a state in which the second and third portions 
located in the central part of the image are displayed, (E) stands for a 
state in which the second partial region beginning from a position apart 
from the upper end of the image by 1/4 of the vertical length thereof is 
displayed. Selection of any display state above can be arbitrarily 
specified from the keyboard 7 of FIG. 7; furthermore, a sequential display 
of images can also be arbitrarily specified in the forward or reverse 
direction. 
In FIG. 7, reference numeral 71 is a command input key for flipping the 
page of the image in the forward direction to display the next page, 
reference numeral 72 indicates a command input key for flipping the page 
of the image in the reverse direction to display the next page, reference 
numeral 73 denotes a command input key for successively flipping pages in 
the forward direction to sequentially display the image pages until a stop 
key 70 is pressed, and reference numeral 74 stands for a command input key 
for successively flipping pages in the reverse direction to sequentially 
display the pages. A change of the display size is accomplished by use of 
ten-key keys 75-78 corresponding to the digits indicated between (A) and 
(B) and between (B) and (C) of FIG. 6, whereas a change of the display 
position is achieved by use of cursor keys 79-80 associated with arrow 
marks shown between (B) and (C) and between (C) and (E) of FIG. 6. The 
size of an image to be displayed by means of a ten-key key with a number j 
is here assumed to be 
##EQU2## 
and the value of P is set to "4". Furthermore, the amount of a change of 
the display position to be changed by means of cursor keys 79-80 is to be 
equivalent to 
##EQU3## 
for each operation. Incidentally, a set of keys 82 of the keyboard 7 of 
FIG. 7 are disposed to input character strings such as an index. 
The retrieval function above is realized through control sequences of FIG. 
5B-FIG. 5D to be executed when a retrieve command is inputted. First, in 
step 134, an index of objective image data, for example, "TOKKYO (patent)" 
is inputted from the keyboard 7. The supplied index is stored in a 
predetermined area of the work memory 10, and then in step 136, the index 
file 3D is searched to retrieve a record associated with the index. This 
retrieval of the record is performed in a procedure such that the data is 
sequentially read from the index file 3B so as to be loaded in the work 
memory 10 where the character string of the index undergoes a matching 
operation. A set of retrieved index records are stored as a record table 
80 of FIG. 8 in the work memory 10. Each record includes, like the 
constitution of FIG. 4, an index field 81 and address fields 82-i and 83-i 
and a size field 84-i for each partial region. In this diagram, l 
indicates the data count of data searched by the index retrieval. 
In the subsequent step 138, a variable "SIZE" indicating the size of the 
display image and a variable "POS" denoting the start position of the 
display partial region are initialized. Here, the variables "SIZE" and 
"POS" are to be specified by using 1/P of the overall image as the unit 
and the initial values of "SIZE" and "POS" are assumed to be "P" and "O", 
respectively, which namely corresponds to the state (A) of FIG. 6 
displaying the entire image. In step 140, the image display specification 
parameter j for the next image to be displayed is initialized to "O" and 
11A is specified for the buffer memory to store the next image read from 
the image file 3A. In step 142 waiting for a command input from the 
operator, when the command input is received, step 144 is effected to 
check for the validity of the inputted command. The program here 
recognizes the validity only for the forward-directional successive 
display command C1 associated with the key 73, the forward-directional 
one-page display command C2 corresponding to the key 71, the 
reverse-directional successive display command C3 for the key 74, the 
reverse-directional one-page display command C4 associated with the key 
72, and an end command for the keys 75-78 changing the display size and 
the keys 79-81 changing the display position. Furthermore, the program 
regards as invalid, like an input of an undefined command, an input of a 
forward-directional display command in a state where the last image having 
the image number l is being displayed and an input of a 
reverse-directional display command in a state where the first image 
having the image number 1 is being displayed. In step 148, the display 
direction of the command is judged to be the forward direction (C1 or C2) 
or the reverse direction (C3 or C4) so as to proceed to step 150 or 152, 
and then the parameter number j specifying the next image to be read is 
determined. 
In step 154, it is checked to determine whether or not a command to change 
the display size or position has already been inputted. If such a command 
has already been received, the variables SIZE and POS are changed. 
FIG. 9 is a detailed flowchart of a subroutine associated with the step 
154. In step 802, the program judges whether or not keys 75-78 of the 
ten-key pad have been inputted, namely, whether or not a command changing 
the display size has been received. If the command has been inputted, a 
sequence of steps 804-814 is executed. In step 804, when it is confirmed 
that the specified new size is not equal to the current size, step 806 is 
accomplished to judge whether or not the new size is less than the present 
size. If this is the case, step 808 is achieved to clear on the bit map 
memory 13 a portion which is being displayed and which becomes not to be 
displayed thereafter. In step 810, it is judged whether or not the image 
exceeds the lower limit when the image is changed to the specified size at 
the current display position. If the lower limit is exceeded, the position 
POS is moved upward until the bottom end of the display 5 matches with the 
bottom end of the image. Finally, in step 814, the size variable SIZE is 
changed. 
In the step 802, if the size change command has not been inputted yet, step 
816 is executed to judge whether or not a command to move the display 
position downward has already been inputted. If the command has already 
been received, step 818 is achieved and when it is confirmed here that the 
current position is other than the bottom end, control is passed to step 
820 to clear on the bit map memory 13 a portion which is being displayed 
and which becomes not to displayed after the display position is moved. 
Finally, in step 822, the value of the variable POS is incremented to move 
the display partial region downward. 
If a downward move command has not been inputted yet, control proceeds to 
step 824 to judge whether or not an upward move command has already been 
received. If such a command has already been inputted, steps 826-830 are 
executed. In a sequence of the steps 826-830, the display position is 
moved upward according to the same idea applied to the sequence of the 
steps 816-822 above. Incidentally, in this subroutine, in order to receive 
in an arbitrary sequence a command to change the size of the display 
region and a command to change the position thereof, control returns to 
the first step 802 after the processing of a command is completed and then 
it is again judged whether or not the next command has already been 
received. 
Returning now to FIG. 5B, in the next step 156, referring to a record 
having an image number j in the table of FIG. 8, subdivided image data is 
read from a region of the optical disk 3 ranging from the Aj' (POS)-th 
sector to the Aj' (POS+SIZE -1)-th sector, the number of sectors thus read 
corresponding to the value of "SIZE", and then the subdivided image data 
is stored in a predetermined buffer memory. Although whether or not the 
buffer memory 11A or 11B is assigned for the read operation is determined 
depending on the pertinent state as will be described later, in the 
initial state, the subdivided image data is stored in the buffer memory 
11A established in step 140. In step 158, when it is confirmed that the 
read operation of the image data is completed, step 160 is accomplished to 
change over the buffer memory for the next image data from the buffer 
memory 11A to the buffer memory 11B (from 11B to 11A in the next 
change-over operation). Thereafter, if a command inputted in the step 142 
is a forward-directional display command, the steps 164-186 of FIG. 5C are 
effected. If the command is a reverse-directional display command, the 
steps 188-210 of FIG. 5D are executed. 
In a case of a forward-directional display command, the step 164 is 
achieved to compare j with l. If the latest image read out is not the 
final retrieval data having the image number l, steps 166-182 are 
executed. In the step 166, the decode processor 15 restores the compressed 
image data having the image number l stored in the buffer memory 11A or 
11B and the restored data is stored in the bit map memory 13. The image 
data to be restored is assumed to range from the a.sub.j (POS)-th bit to 
the bit of B.sub.j (POS)+B.sub.j (POS)+. . . B.sub.j (POS+SIZE-1). In step 
168, the subroutine of FIG. 9 is executed again and then step 170 is 
achieved to read the (j+1)-th image into a buffer memory which is 
different from the buffer memory storing the j-th image. The restore 
processing of the step 166 and the read processing of the step 170 are 
concurrently accomplished by using the bus 17 in a time sharing fashion. 
In steps 172 and 174, it is confirmed that the restore processing and the 
read processing are completed; thereafter, step 176 is executed to confirm 
whether or not a stop command has been inputted by the operator. If this 
is the case, control returns to the command input wait state in the step 
142; otherwise, step 178 is effected to achieve the change-over operation 
between the buffer memories 11A and 11B for the next image data to be 
read. In the next step 180, it is judged whether the received command is 
the forward-directional successive display command or the 
forward-directional one-page display command. For the former, step 182 is 
executed and then the sequence beginning from the step 164 is repeated. 
For the latter, control returns to the command input wait state in the 
step 142. In the case where the image read in the step 164 is judged to be 
the last data, since the next image data need not be read out, only the 
steps 184 and 186 corresponding to the steps 168 and 172 are executed and 
then control enters the command input wait state in the step 142. 
The sequence of steps 188-210 to be achieved when a reverse-directional 
display command is inputted is the same as the sequence of steps 164-186 
described above except that the image read sequence is reversed; 
consequently, details thereabout will not be described. 
Incidentally, as can be seen from the description of operations above, 
since the registration and the retrieval are effected in the different 
modes, the memory 13 necessary only for the registration can be physically 
used for the memory 11A or 11B. Furthermore, in the embodiment above, 
although the registration and the retrieval are possible in the image file 
system, the image file medium can be removed from the system so as to be 
installed in another system. Consequently, a system only for the register 
processing and a system only with the retrieval function may be separately 
installed. Moreover, in the embodiment above, although the original image 
is subdivided by the divisor P into partial regions of the same size, the 
partial regions may be of the predetermined different sizes or the 
subdividing positions may be varied depending on the size of the original 
image. In addition, as information indicating the state of subdivision, 
information of the size and position of each partial region is stored in 
the index file in the embodiment; however, it may also be possible to 
store either size information or position information and to calculate 
information not stored when an image is retrieved. Furthermore, in the 
embodiment above, although an index record is generated for each image, 
the index record may be prepared for each partial region. 
Next, a description will be given of a second embodiment according to the 
present invention. In the second embodiment, the image data record is not 
beforehand subdivided and is directly recorded in the image file 3A and 
when a retrieval image is read from the image file, an image data store 
location (region) substantially associated with a partial region specified 
by the operator is calculated so as to selectively read out a portion of 
the image data, thereby displaying the image data portion on the display 
5. 
That is, in the case where image data is registered to the image file 3A, 
as shown in FIG. 10, when an index is inputted in step 114, the entire 
input image is encoded (compressed) and then the resultant image is 
written in the image file region 3A of the optical disk 3 in step 128. 
Furthermore, in step 130, an index record is written in the index file 
region 3B. The index record in this case includes, as shown in FIG. 11, an 
index field 41, a field 42 for storing a sector number in the image file 
3A indicating a store address of a compressed image data record associated 
with the index, and a field 44 for storing a byte count indicating the 
length of the compressed image data. In this diagram, image data D(m), 
D(m+1), and D(m+2) corresponding to index records m, m+1, and m+2 are 
stored in recording areas beginning from sector address A(m), A(m+1), and 
A(m+2), respectively of the image file region 3A and are of lengths S(m), 
S(m+1), and S(m+2), respectively. 
The file search operation on a file storing indices and image data in the 
format above is also effected according to the control procedure shown in 
FIGS. 5B-5D. That is, a set of index records retrieved by the index search 
(step 136) of FIG. 5B are recorded on the work memory 10 as a record table 
80' of FIG. 12. Each record includes an index field 81, an address field 
82 of the image data, and a field 83 indicating the length of the image 
data. 
The size variable SIZE of a partial image to be displayed and the variable 
POS of an extract position of the partial image are specified in the 
similar fashion to that applied to the first embodiment. In step 156, the 
identification of the image data read region is achieved as follows, for 
example. Namely, in the case where an image D(mj) corresponding to the 
j-th record is read from the record table 80', the first sector of the 
image data read region and the last sector thereof are attained from 
expressions (1) - (2), respectively as follows. 
EQU A(mj)+[S(mj).multidot.(POS/P)/K]-.alpha. (1) 
EQU A(mj)+[S(mj).multidot.{(POS+SIZE)/P}/K]+.beta. (2) 
where, K is the number of data bytes per sector, .alpha. and .beta. 
indicate a predetermined positive constant or zero, and the symbol [x] is 
the Gaussian symbol meaning that an integer is attained by truncating the 
value of x. Determination of the image data read region through the 
calculations above is based on an idea that the content of each partial 
region attained by subdividing the original image by the divisor P, the 
partial region being of the same size, can be substantially read out by 
providing margins .alpha. and .beta. for the partial regions thus 
obtained. 
FIG. 13 is a schematic diagram illustrating corresponding relationships 
between the partial regions of the compressed image data 30 recorded in 
the image file region 3A and the partial regions of the image 20 attained 
by restoring the partial regions of the compressed image data 30. In this 
example, the compressed image 30 is equally subdivided into P (=4) partial 
regions 31-34. In this case, marginal sectors .alpha. and .beta. are 
additionally assigned for the third partial region 33 to establish a read 
region 36. In the case where the compressed image 30 is compressed through 
such an encoding operation as that of the Modified Huffman encode method 
described in the paper above in which the separation between lines of the 
original image is retained, the last position of each line is located in 
the compressed image as indicated by a code "EOL". The EOL code comprises 
a particular bit pattern, for example, including at least a predetermined 
number of "O's" followed by a "1" bit and can be extracted through a 
string matching operation from an arbitrary code string read from the 
file. When the compressed image includes an EOL code, data (shaded 
portion) preceding the first EOL in the marginal region .alpha. and data 
succeeding the last EOL in the marginal region .beta. each may possibly be 
separated at an intermediate point of a line or a code in the restored 
image. Consequently, these data are to be removed before the image is 
restored by the decode processor 15 in the step 166 of FIG. 5C, in other 
words, the data portion ranging from the first EOL code to the last EOL 
code in the read region 36 is subjected to the restore processing so as to 
be displayed on the display 5. 
In the embodiment above, when a plurality of images are displayed by 
flipping image pages, the time interval to change the page is determined 
according to the size of the partial region of the image to be displayed. 
However, the time interval may also be set to be adjustable through a key 
operation, for example, like the case of the operations of acceleration 
and braking of a car. 
FIG. 14 is an example of a flowchart to control a routine implementing the 
adjustment of the time interval. The first step 302 judges whether or not 
a time adjust command has been inputted from the keyboard 7 to indicate 
the operation of the acceleration or braking. 
If the time adjust command has already been received, the program (step 
304) judges whether the type of the input command is "accelerate" or 
"brake". For an "accelerate" indication of the input command, step 306 is 
executed to reduce the value of the wait time parameter t (to be described 
later) by a preset time value .DELTA.t. In the case where the value of t 
becomes to be negative as a result of the subtraction, a correction is 
effected to obtain t=0 (steps 308-310). If the type of the input command 
is "brake", the value of t is increased by a predetermined value .DELTA.t 
in step 312. In this case, the value of t is limited to the maximum value 
t.sub.max (step 314-315). Step 320 is a time adjust processing step to 
achieve the loop processing a number of times corresponding to the wait 
time parameter t. 
The time adjusting routine is inserted, for example, immediately before the 
buffer memory changeover steps 160, 178, and 202 in the flowcharts of 
FIGS. 5B, 5C, and 5D, respectively. The initial value of the parameter t 
here need only be set as t=0 in the step 138. In the flowchart of FIG. 14, 
although the time interval in changed by the time of .+-..DELTA.t each 
time the image is changed on the display 5, in order to increase the 
magnitude of the change, the value of .DELTA.t need only be set in 
proportion to the depression time of the accelerating or braking pedal. 
In the first and second embodiments above, a position of a partial region 
of the image to be displayed on the display 5 is specified to identify the 
compressed image data portion to be read from the image file. As an 
alternative method (a third embodiment), for example, in response to a 
specification inputted by the operator to indicate a time interval or a 
display cycle for the image change through the successive page flipping 
operation, the compressed data may be read from the image file 3 beginning 
from a reference point, for example, the first data of each image record, 
the amount of the data to be read being associated with the specified time 
interval or the display cycle. The time interval may be specified, for 
example, with reference to an interval of time required to display the 
entire screen image through the ten-key pad, namely, "9" (=90%), 
"8"=(80%), etc. 
Furthermore, in the cases of the first and second embodiments, since the 
amount of information included in a partial region to be displayed in the 
screen varies among the image pages, if compressed image data constituting 
a partial region of a specified size of a page is read out and the 
operation to read the compressed image data of the next page is initiated 
immediately thereafter, the display time in the display screen varies 
between the image pages. To minimize the variation in the display time of 
the pages, a standard value of the display time interval need only be 
established such that for a display cycle associated with a data amount 
less than that of the standard display time interval, the time interval 
adjusting routine is executed to delay the operation to read the next 
retrieval image. Although the standard display time interval may be 
specified by the operator, it may also be possible that in the step 136 
and/or the steps 154, 168, and 192 of the flowcharts of FIGS. 5B-5D, the 
contents of the table 80 are searched to find an image having the maximum 
amount of data with respect to the size of the partial region to be 
displayed, thereby setting the standard display time interval to be equal 
to the interval of time necessary for displaying the image. In this case, 
it is only necessary to effect a time adjustment corresponding to the 
difference between the maximum amount and the amount of data of the 
partial region to be subsequently display immediately before the steps 
160, 178, and 202 in the similar fashion to that applied to the routine of 
FIG. 14. If an effect due to a size change of a partial region during a 
retrieval processing need not be considered, the image having the maximum 
data amount may be detected only through the step 136. 
In the embodiments above, since an image is displayed for an image, the 
display position on the display 5 is basically invariant even when the 
position and size of the partial image specified to be displayed are 
changed. However, the display positions of the respective images may be 
changed so as to display a plurality of images for an image. FIG. 15 is a 
schematic diagram of display contents on the display 5 in the case where 
two partial image data obtained in the state (A) or (B) of FIG. 6 are 
displayed for each image. The digit enclosed by a circle indicates an 
image number. In this example, the digits alternately indicate the 
pertinent partial region of the next image in the upper and lower half of 
the image. FIG. 16 shows display contents on the display 5 in the case 
where four partial image data obtained in the state (C) or (E) of FIG. 6 
are displayed for each image. In this case, the pertinent partial image of 
the next image is cyclically displayed in a display region obtained by 
equally subdividing the image by four. The display format can be easily 
implemented by sequentially changing the address of the bit memory map 16 
storing the restored image in the steps 166, 184, 190, and 208 of the 
flowcharts of FIGS. 5B-5D. 
As can be seen from the description above, according to the present 
invention, since a part of image data encoded and then stored in a file is 
selectively read therefrom so as to be decoded to obtain a display image, 
when a plurality of retrieved images are sequentially displayed, the 
period of time required to display all images can be minimized. As a 
result, when the operator knows the substantial position of a 
characteristic part of an objective image to be displayed, the objective 
image can be selected at a high speed from a plurality of images. 
While the invention has been described with reference to the particular 
illustrative embodiments, it is not restricted by those embodiments but 
only by the appended claims. It is to be appreciated that those skilled in 
the art can change and modify the embodiments without departing from the 
scope and spirit of the invention.