JPH05210382A - Image display device - Google Patents

Abstract

PURPOSE:To designate the position of an image, which is expressed by image data, at high speed while reducing the number of operations with high accuracy. CONSTITUTION:A thinning ratio for displaying all the areas of the image expressed by origin image data stored in an image memory 12 on the display screen of a color display 18 with no zoom is calculated, the origin image data are thinned at the thinning ratio by an image processing processor 16, and an image represented by the thinned origin image data is displayed by a display controller 20. The image to be displayed is displayed by a display address controller 20d while being zoomed at a prescribed magnification. Further, when the redisplay key of a tablet 14 is operated, a thinning ratio for displaying the range of the image to be displayed on the display screen without zooming display is calculated, the image data are thinned based on the thinning ratio by the processor 16, and the image represented by the thinned image data is displayed by the display controller 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention displays an image represented by image data stored in an image memory or the like on a display means such as a display and utilizes a cursor provided on the display screen of the display means. The present invention relates to an image display device that specifies a position on image data.

[0002]

2. Description of the Related Art Generally, such an image display device has an image memory for storing image data to be displayed, a display device for displaying an image, and a control for performing drawing on the display device based on the image data stored in the image memory. In addition to the processing device, it also includes a position designating unit such as a mouse or tablet for designating a position on the displayed image. By making full use of the position designating means, the cursor displayed on the display screen of the display device can freely move on the display screen, so that the position on the image is designated by the position of the cursor.

By the way, since the image data stored in the image memory usually comprises a number of pixels much larger than the number of images that can be displayed on the display screen of the display device, the image display device is The data is once thinned at a predetermined thinning rate and then transferred to the display device. Although the position of the image represented by the thinned-out image data is designated by the cursor as described above, the position designation may be difficult because the image on the display screen is too small. Therefore, the image display device is usually provided with a zoom function.

The zoom function enlarges an image based on the thinned-out image data. For example, when the zoom ratio is 2 times, the image data for one line is divided into two.
Enlargement is performed by repeatedly outputting lines, and the position is specified on the enlarged image based on the cursor.

[0005]

However, since the conventional image display device enlarges an image based on the thinned-out image data, the enlarged image is represented by original image data. The image is not faithfully reproduced, and for this reason, the desired position cannot be indicated with high accuracy from the enlarged image.

Therefore, the operator judges whether or not the desired position can be designated from the enlarged image, and when it is judged that the designation is difficult, the operator carries out the following work. This work temporarily returns the image on the display screen to the image before enlargement, specifies an area on the image, and gives an instruction to redisplay the area, and the image display device that received the instruction , A thinning rate is calculated from the ratio of the number of pixels of the image data included in the area and the number of pixels of the display screen, the thinning rate is applied to the original image data, and the thinned image data is obtained. The image is displayed based on.

The image thus redisplayed on the display screen is
Since it reproduces the original image data with high accuracy,
Although it is possible to specify the desired position of the image with high accuracy from the display screen, as described above, many operations are required for the operator to specify the position,
Also, the processing in the image display device becomes complicated.
Therefore, the position designation of the image represented by the image data is
There was a problem that it could not be performed at high speed with a few operations.

The image display apparatus of the present invention has been made in view of these problems, and an object thereof is to specify the position of an image represented by image data at high speed with a high number of operations even though it is highly accurate. ..

[0009]

In order to achieve such an object, the following constitution was adopted as a means for solving the above problems.

That is, the image display device of the present invention is an image display device for displaying an image represented by the image data stored in the image data storage means on the display means, and the image stored in the image data storage means. Thinning processing means for generating thinned display data by subjecting the data to a predetermined thinning rate, and outputting a control signal based on the display data to the display means, thereby displaying the display data. A display control means for displaying an image to be displayed on the display means, and a means included in the display control means for giving a control signal to the display means for zoom-displaying the image displayed on the display means at a specified magnification. The processing means and the position of the cursor are given to the display control means to display the cursor on the display screen of the display means, and the display screen Position designation means for designating an arbitrary position on the image represented by the image data based on the position of the cursor, and an image displayed on the display means is displayed on an image generated by a new thinning rate thinning process. A redisplay command output unit that outputs a redisplay command to the effect of receiving a command from the outside, and a range of an image displayed on the display screen of the display unit when the redisplay command is received. And a thinning rate changing means for calculating a thinning rate to be displayed without zoom display by the zoom processing means and changing the thinning rate for the thinning processing executed by the thinning processing means to the calculated thinning rate. I am trying.

In the image display device, the thinning-out processing means is configured to perform the thinning-out processing according to the thinning-out rate for displaying the entire area of the image represented by the image data stored in the image data storage means on the display screen of the display means. In addition, the basic display data storage unit that continues to store the display data thinned by the thinning processing unit as basic display data even after a new thinning process by the thinning processing unit according to the thinning rate changing unit is executed. May be provided.

[0012]

In the image display device of the present invention having the above-described structure, the image data stored in the image data storage means is thinned by the thinning processing means, and the image represented by the thinned display data is displayed and controlled. The image is displayed on the display means by the means, and the displayed image is zoom-displayed at the designated magnification by the zoom processing means. When the redisplay command is output from the redisplay command output means by receiving an instruction from the outside, the thinning rate changing means does not display the range of the image displayed on the display screen of the display means by the zoom processing means. The thinning rate displayed by is calculated, and the thinning rate executed by the thinning processing unit is changed to the calculated thinning rate.

With such an operation, the image represented by the image data decimated at the decimating rate for displaying the range of the image to be displayed without zoom display can be obtained only by giving an instruction from the outside to operate the redisplay command output means. The image is immediately displayed on the display screen, and the arbitrary position on the image is specified by the position specifying means on the displayed image.

[0014]

Preferred embodiments of the present invention will be described below in order to further clarify the constitution and operation of the present invention described above.

FIG. 1 is a block diagram showing an image display device as an embodiment of the present invention. This image display device
A well-known CPU 1, ROM 3, and RAM 5, an input scanner 10 that reads an original image as raster data, and an image memory that stores the read raster data (original image data) (a huge data capacity that can sufficiently capture an image on a document). Based on the memory) 12, the tablet 14 for performing various instructions and position input on the image, the image processing processor 16 for performing various processes including the thinning process on the original image data, and the image data after the thinning process. Display controller 20 for drawing on the color display 18
And an output scanner 22 that draws on a document based on the original image data.

The tablet 14 is a color display 1
8 is a device for inputting an arbitrary position on the image displayed on the display 8, and is also a device for inputting various instructions and various data. Although the input panel of the tablet 14 is shown in FIG. 2, as shown in FIG. 2, the input panel of the tablet 14 has a position input area k1, an alphabet key group k2, an overview key k3, a fine view key k4, and a zoom key k5. , A scroll key k6, a redisplay key k7, an image input key k8, and the like.

The display controller 20 has two display memories for temporarily storing the image data (display data) decimated by the image processor 16, that is, an overview display memory 20a and a fine view display memory 20b.
And a cross-cursor generation circuit 20c for displaying a cross-shaped cursor on the display screen of the color display 18, and a display capable of zooming the image displayed on the color display 18 by controlling the transfer addresses of the display memories 20a and 20b. An address controller 20d and a D / A converter 20e that converts the image data signals read from the display memories 20a and 20b into analog signals and outputs the analog signals to the color display 18 are provided. The cross-cursor generation circuit 20c displays a cross-shaped cursor on the display screen of the color display 18 as described above. The cross-cursor generation circuit 20c receives position information from the tablet 14 according to the operation of the position input area k1 of the tablet 14, and Move the cursor freely according to the position information.

The CPU 1 has an image input processing section 1a, a zoom / scroll processing section 1b, and a redisplay processing section 1c. It should be noted that these processing units represent the contents of the processing executed by the CPU 1 according to a predetermined program stored in advance in the ROM 3, and these processing will be described in detail below.

FIG. 3 is a flow chart showing an image input processing routine corresponding to the image input processing section 1a. In this image input processing routine, the operator inputs the image input key k8 of the tablet 14 to perform "image input".
When the CPU 1 determines that the instruction of
It is executed by U1.

When the processing is started, the CPU 1 firstly
An instruction to start reading the original image is sent to the input scanner 10 (step 110). The input scanner 10 that has received the reading start instruction executes an image reading process of scanning the original image and reading the original image data (step 120).

Thereafter, the CPU 1 inputs the original image data read by the input scanner 10, transfers it to the image memory 12 and stores it (step 130). Then, based on the number of images of the original image data stored in the image memory 12 and the number of pixels of the display screen of the color display 18 stored in advance, the entire area of the image represented by the original image data is displayed by the color display 18 The thinning rate A to be displayed on the display screen is calculated (step 140).

Subsequently, the CPU 1 controls the display controller 2
A process for setting the environment for display to 0 is performed (step 150). Specifically, the display controller 20
To the display address controller 20d, and the display address controller 20d is instructed to set the display magnification to 1.

The display controller 20 which has received such an instruction sets the environment according to the instruction (step 160). That is, the display controller 20 uses the overview display memory 20 as a memory for extracting image data.
Settings such as selecting a and increasing the magnification of the display address controller 20d to 1 are made.

After executing the processing of step 150, the CPU 1 continuously stores the original image data from the image memory 12 in the RAM.
5, and sends to the image processor 16 an instruction to start executing the thinning-out process of the thinning-out rate A calculated in step 140 (step 170). The image processor 16 that has received this instruction performs the thinning process of the thinning rate A that has received the instruction from step 170 on the original image data stored in the RAM 5 (step 180).

On the other hand, the display controller 20, which has completed the environment setting in step 160, receives the image data subjected to the thinning process in step 180 (step 19).
0). The thinned image data thus received is stored in the overview display memory 20a. Then, the display controller 20 displays an image on the color display 18 according to the environment set in step 160 (step 195). That is, the display controller 2
0 indicates that the image data is taken out from the overview display memory 20a according to the setting environment and the display magnification is 1 ×,
The image represented by the image data is displayed on the color display 18.

FIG. 4 is a flowchart showing a zoom processing routine corresponding to the zoom-related portion of the zoom / scroll processing unit 1b. This image input processing routine is performed by the operator using the zoom key k5 of the tablet 14.
CP is input, and "Zoom" is instructed.
When U1 determines, it is executed by CPU1. When the processing is started, the CPU 1 first sends an instruction to start the zoom-up processing to the display controller 20 (step 210).

The display controller 20, which has received this start instruction, executes a zoom-up process for enlarging the image displayed on the color display 18 to a predetermined magnification (two in this embodiment) (step 220). ).
Specifically, the display address controller 20d is operated to double the number of 1 pixel data stored at each address from the overview display memory 20a or the fine view display memory 20b on the side currently being displayed. The pixel data of is output. Specifically, the image data for one line stored in the display memories 20a and 20b is repeatedly output for two lines. In this way, the image displayed on the color display 18 is doubled. When the zoom key k5 is operated again, the zoom key k5 is further doubled, and as a result, the image displayed by the image input processing routine is magnified four times.

On the other hand, the CPU 1 thereafter carries out an operation of multiplying the counter Z representing the display magnification by 2 which is the value of the predetermined magnification (step 230). Step 23
After executing 0, the processing of this routine is ended.

FIG. 5 is a flowchart showing a scroll processing routine corresponding to the scroll-related portion of the zoom / scroll processing unit 1b. This scroll processing routine is executed by the CPU 1 when the CPU 1 determines that the operator has input the scroll key k6 of the tablet 14 to instruct “scroll”. When the process is started, the CPU 1 first sends an instruction to start the scroll process to the display controller 20 (step 310).

The display controller 20, which has received the start instruction, executes a scroll process of scrolling the image displayed on the display screen of the color display 18 by a predetermined amount (step 320). The scroll processing is for scrolling the image enlarged and displayed by the zoom-up processing, and displays the offset position of the display address in the overview display memory 20a or the fine view display memory 20b on the side currently being displayed. Made by changing. It should be noted that the scroll process is described only when the image on the display screen is moved in one direction, but the tablet 14
When the scroll direction is input from, the scroll can be performed in that direction.

After that, the CPU 1 executes the process of calculating and storing the offset position by the scrolling process (step 330). After the execution of step 330, the processing of this routine ends.

FIG. 6 is a flowchart showing a redisplay processing routine corresponding to the redisplay processing section 1c. This redisplay processing routine is performed by the operator using the tablet 14
When the CPU 1 determines that the "redisplay" instruction has been made by pressing the redisplay key k7, the CPU 1 executes the process. When the processing is started, the CPU 1 first
A process of calculating the image range displayed on the display screen of the color display 18 is executed (step 410). The image range is obtained by the upper left coordinate value and the lower right coordinate value indicating a rectangular area on the image data stored in the overview display memory 20a (or the fine view display memory 20b).

Subsequently, the color display 18 is performed without zoom-up display of the image range by zoom-up processing.
The thinning rate B to be displayed on the display screen is calculated (step 420). Specifically, the thinning rate of the image data representing the image currently displayed on the display screen, the zoom display magnification Z
The thinning rate B is calculated by multiplying by. The image currently displayed on the display screen is the overview display memory 2
0a, the thinning rate A calculated in step 140 of the image input processing routine.
The thinning rate B is calculated by multiplying by the display magnification Z calculated in step 230 of the zoom processing routine. The thinning rate B may be obtained from the ratio of the number of pixels of the image data in the image range calculated in step 410 to the number of pixels of the display screen of the color display 18.

Subsequently, the CPU 1 controls the display controller 2
A process for setting the display environment for 0 is performed (step 430). Specifically, the display controller 20
To the display address controller 20d, and the display address controller 20d is instructed to set the display magnification to 1.

The display controller 20, which has received such an instruction, sets the environment in accordance with the instruction (step 440). That is, the display controller 20 uses the fine view display memory 2 as a memory for extracting image data.
Select 0b, display address controller 20d
Settings such as setting the enlargement ratio of 1 to 1 are made. CP
After executing the process of step 430, the U1 subsequently inputs the original image data from the image memory 12 to the RAM 5, and starts executing the thinning process of the thinning rate B calculated in step 420 to the image processor 16. An instruction to that effect is sent (step 440).

The image processor 16 which has received this instruction
Performs the thinning process of the thinning rate B instructed from step 450 (step 460). On the other hand, step 4
The display controller 20, which has completed the environment setting in 40, receives the image data thinned by the image processor 16 (step 470). The thinned image data thus received is stored in the fine view display memory 20b. Then, the display controller 20
Displays an image on the color display 18 according to the environment set in step 440 (step 48).
0). That is, the display controller 20 fetches the image data from the fine view display memory 20b according to the setting environment and displays the image represented by the image data on the color display 18 at a display magnification of 1.

The configuration of another part of the image display device of this embodiment will be described. As described above, the display controller 20 has an overview display memory 20a in which image data indicating the entire area of the original image data is stored and a fine view in which image data indicating a partial area of the original image data is stored. In this embodiment, the overview key k3 of the tablet 14 is included because the display memory 20b for display is provided.
By operating the and fine view key k4, either of the display memories 20a and 20b is manually selected. That is, when the overview key k3 is operated, the image data is retrieved from the overview display memory 20a and the image showing the entire area of the original image data is displayed on the color display 18, and the fine view display memory 20b is displayed. When operated, an image is taken out from the fine view display memory 20b and image data showing a partial area of the original image data is displayed.

Regarding the operation of the image display device of this embodiment,
It will be described next. When drawing a straight line on the display screen of the color display 18, the operator operates the tablet 14 to specify a predetermined point with the cross cursor on the display screen. First, how the operator performs this position designation work will be described. FIG. 7 shows the work procedure performed by this operator.

As shown in FIG. 7, the operator first
Color display 18 according to the image input processing routine
It is determined whether or not the predetermined point can be designated on the image (current image) displayed on the screen (step 510). If it is determined that the tablet 14 can be designated, no special processing is required, so this routine is terminated and the position designation using the tablet 14 is performed.

On the other hand, if it is determined in step 510 that the specified point cannot be specified, then it is determined based on past experience whether or not the specified point can be specified when the display image is zoomed up. Judge (step 52)
0). Here, if it is determined that the zoom-up processing can be designated, then the zoom key k5 of the tablet 14 is operated to instruct execution of the zoom-up processing (step 530). At this time, execution of scroll processing is also instructed if necessary.

Subsequently, it is determined whether or not the predetermined point can be designated on the display screen (step 540). When it is determined that the designated point can be designated, this routine is ended and the position designation using the tablet 14 is performed. Do the work. On the other hand, step 5
If it is determined at 40 that the designation is not possible, the redisplay key k7 of the tablet 14 is operated to instruct execution of the redisplay processing (step 550). When the redisplay processing is executed, the image displayed on the display screen becomes an image represented by the image data subjected to the thinning processing of the thinning rate displayed without zoom display. Therefore, the displayed image has high accuracy, and it becomes easy to specify the predetermined point. After performing step 550, the process proceeds to step 510.
Then, it is judged whether or not the predetermined point can be designated on the current image, and the steps after step 510 are repeatedly executed.

If it is determined in step 520 that points cannot be specified even if zoom-up processing is performed,
Using the tablet 14 on the display image, two points at both ends of the rectangular diagonal line are designated (step 560), and an instruction to redisplay the image of the designated area on the color display 18 is input. Although this re-display work has not been described so far, it is a well-known work for extracting the data of the area from the actual image data, thinning the extracted data at a predetermined thinning rate, and displaying the thinned data on the color display 18. Is. After that, the process returns to step 510, and the subsequent steps are repeatedly executed.

Next, how the displayed image changes according to the work procedure by the operator will be described below with a specific example. FIG. 8 is an explanatory diagram showing changes in the image displayed on the display screen of the color display 18. As shown in FIG. 8A, alphabets "B" to "P" are displayed on the display screen. This image corresponds to the entire area of the image represented by the original image data, and is a non-zoom image according to the image data stored in the overview display memory 20a by the image input processing routine. If the operator determines that a predetermined point cannot be designated on this image (step 510) and determines that the position can be designated after performing the zoom-up processing (step 520), the operator instructs execution of the zoom-up processing. (Step 530). As a result, as shown in FIG. 8B, an image that has been zoomed in twice based on the image data stored in the overview display memory 20a is displayed on the display screen.

When it is determined that the predetermined point cannot be designated even after the zoom-up processing is performed, the execution of the zoom-up processing is further instructed. As a result, as shown in FIG. 8C, an image that has been zoomed in 4 times based on the image data stored in the overview display memory 20a is displayed on the display screen. After that, as a result of scrolling the image as necessary, the image is displayed as shown in FIG.

Since the image shown in FIG. 8D is an image which has been zoomed up based on the image data stored in the overview display memory 20a, the image represented by the original image data. Is not faithfully reproduced, and the image becomes a rattling image (a rattling image in units of 4 pixels) as indicated by a broken circle in (d) of FIG. Therefore, the operator determines that the predetermined point cannot be designated on the image (step 540), and instructs the execution of the redisplay processing (step 550).

As a result, the image displayed on the display screen is
Image data subjected to a thinning process of a thinning rate for displaying the image range shown in FIG. 8D without zoom display,
That is, a non-zoom image is obtained according to the image data stored in the fine-view display memory 20b by the redisplay processing routine ((e) in FIG. 8). Therefore, the displayed image is drawn by a smooth curve as shown in the broken circle in (e) of FIG. 8, which facilitates the position designation on the display screen.

Even in the case of the image shown in FIG. 8E, if the displayed image is so fine that it is difficult to specify the position, further execution of zoom-up processing is instructed. As a result, as shown in FIG. 8 (f), an image that has been zoomed in twice based on the image data stored in the fine view display memory 20b is displayed on the display screen. After that, as a result of scrolling the image as needed, the image is displayed as shown in FIG.

Since the image shown in (g) of FIG. 8 is an image which has been zoomed up based on the image data stored in the fine view display memory 20b, the image shown in (g) of FIG. As shown in the circle of the broken line, the image becomes a rattling image (a rattling image in units of 2 pixels). Therefore, the operator determines that the predetermined point cannot be designated on the image, and again instructs execution of the redisplay processing.
As a result, the image displayed on the display screen is (h) in FIG.
As indicated by the dashed circle in the drawing, it is drawn with a smooth curve, which makes it easy to specify the position on the display screen.

As described above, in the image display apparatus of this embodiment, the thinning rate for displaying the entire area of the image represented by the original image data stored in the image memory 12 on the display screen of the color display 18 without zooming. Is calculated, the image processing processor 16 performs thinning processing on the original image data, and the image represented by the thinned image data is displayed on the color display 18 by the display controller 20. Further, the displayed image is zoom-displayed at a predetermined magnification by the display address controller 20d. Further, when the redisplay key k7 of the tablet 14 is operated, the thinning rate for displaying the range of the image displayed on the display screen of the color display 18 without zoom display is calculated, and the image processing processor 16 calculates the original image data. Then, the thinning-out processing is performed on the thinning rate, and the image represented by the thinned image data is displayed on the color display 18 by the display controller 20.

Therefore, only by operating the redisplay key k7 of the tablet 14, the zoomed image on the display screen of the color display 18 is displayed by the thinned image data at the thinning rate displayed without zooming. The image will be changed. Therefore, if it is difficult to specify a desired position from the zoomed image, the tablet 14
Only by operating the redisplay key k7, a highly accurate image can be immediately obtained and its position can be easily designated.

In the image display device of this embodiment, by operating the overview key k3 and the fine view key k4 of the tablet 14, the image displayed on the color display 18 is displayed in the overview display memory 2
The image showing the entire region of the original image data based on the image data from 0a and the image showing the partial region of the original image data based on the image data from the fine view display memory 20b can be immediately switched, and used. It is selfish.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to such an embodiment. For example, original image data read by the input scanner 10 is stored in the image memory 12. Instead of directly importing,
The original image data read by the input scanner 10 may be stored in an auxiliary storage device such as a magnetic disk device and then loaded into the image memory 12 in various modes without departing from the scope of the present invention. Of course you can.

[0053]

As described above in detail, according to the image display device of the present invention, the image displayed on the display screen of the display means without zooming can be thinned out by simply giving an instruction from the outside. The image is changed to an image represented by image data thinned out at a rate. Therefore, when it is difficult to specify a desired position from the zoomed image, a highly accurate image can be immediately obtained only by giving an external instruction, and the position can be easily specified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an image display device as an embodiment of the present invention.

FIG. 2 is a tablet 14 used in the image display device.
It is an explanatory view showing an input panel of.

FIG. 3 is a flowchart showing an image input processing routine executed by CPU 1 together with processing executed by image processing processor 16 and display controller 20.

FIG. 4 is a flowchart showing a zoom processing routine executed by CPU 1 together with processing executed by display controller 20.

FIG. 5 is a flowchart showing a scroll processing routine executed by CPU 1 together with processing executed by display controller 20.

FIG. 6 is a flowchart showing a redisplay processing routine executed by CPU 1 together with processing executed by image processing processor 16 and display controller 20.

FIG. 7 is a flowchart showing work performed by an operator for specifying a position.

FIG. 8 is an explanatory diagram illustrating changes in an image displayed on the display screen of the color display 18.

[Explanation of symbols]

 1 CPU 1a Image input processing unit 1b Zoom / scroll processing unit 1c Redisplay processing unit 10 Input scanner 12 Image memory 14 Tablet 16 Image processor 18 Color display 20 Display controller 20a Overview display memory 20b Fine view display memory 20c Cross Cursor generation circuit 20d Display address controller k1 Position input area k5 Zoom key k6 Scroll key k7 Redisplay key k8 Image input key

Claims (2)

[Claims] 1. An image display device for displaying an image represented by the image data stored in the image data storage means on a display means, the image data stored in the image data storage means being thinned by a predetermined thinning rate. Displaying an image represented by the display data on the display means by outputting a control signal based on the display data to the display means, and a thinning processing means for generating thinned display data by performing processing. Display control means for causing the display control means to include a zoom processing means for giving to the display means a control signal for zoom-displaying an image displayed on the display means at a specified magnification; The cursor is displayed on the display screen of the display unit by giving it to the display control unit, and the position of the cursor on the display screen is displayed. Position designation means for designating an arbitrary position on the image represented by the image data based on the above, and re-displaying the image displayed on the display means on the image generated according to the new thinning rate thinning processing. Redisplay command output means for outputting a display command in response to an instruction from the outside, and, when receiving the redisplay command, the range of the image displayed on the display screen of the display means is zoomed by the zoom processing means. An image display device, comprising: a thinning-out rate to be displayed without displaying, and a thinning-out rate changing means for changing the thinning-out rate executed by the thinning-out processing means to the calculated thinning-out rate. 2. The image display device according to claim 1, wherein the thinning-out processing means displays the entire area of the image represented by the image data stored in the image data storage means on the display screen of the display means. The thinning processing is performed according to the rate, and further, after the new thinning processing by the thinning processing means according to the thinning rate changing means is executed, the display data thinned by the thinning processing means is used as basic display data. An image display device having a basic display data storage means for continuously storing.