JPH06324660A - Superimposing display device - Google Patents

Abstract

PURPOSE:To distinctively display images of similar colors or the same color even when they are displayed one over the other. CONSTITUTION:A display control circuit 7 reads respective pixel data DL and DU out of image memories 5L and 5U stored with color image data generated by composing one pixel multi-bit data of an R, a G, and a B signal and as for each pixel data, a look-up table 9 is used to decide whether or not the border color bit data BL of pixel data L corresponding to the most significant digit bit of the G signal set as a border color bit is equal to border color bit data BU of the pixel data DU. When they are equal, all the bits of the G signal of the pixel data DU are set to the inverted value of the border color bit data BU to generate output pixel data DU' and a superimposing circuit 11 superimposes the output pixel data DU' on the pixel data DL and outputs the result to a color CRT display 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved overlay display device for displaying a plurality of images in a display device or the like.

[0002]

2. Description of the Related Art Conventionally, when a plurality of images are superimposed and displayed on a display device or the like, the display color of the lower image and
If the display color of the superimposed image to be superimposed on this lower image is the same color or a similar color, the superimposed image may not be visible or may be difficult to see. Depending on the program, logical images etc. are performed based on the color image data of the lower side image and the superposed image to superpose the images, and the superposed image is drawn in consideration of the background color of the lower side image, etc. The superposed images are displayed in a superposed manner by preliminarily framing the superposed images and adding a shadow.

[0003]

However, in the above-mentioned conventional overlay display device, the display color of the overlay image must be changed or bordered based on the display color of the lower image. However, it is necessary to always recognize the display color of the lower image, and since complicated drawing processing such as edging and shading is performed, there is an unsolved problem that a processing load is imposed.

Therefore, according to the present invention, even when a plurality of images of the same color or the same color are superimposed and displayed, the superimposed image is surely identified and displayed without paying attention to the display color of the lower image. It is an object of the present invention to provide an overlay display device capable of performing the above.

[0005]

In order to achieve the above object, an overlay display device according to a first aspect of the present invention is arranged such that a pixel is sequentially read from a plurality of image memories that store color image data in which one pixel data is composed of a plurality of bits. In a superposition display device that reads out data and superimposes and outputs pixel data read out from each image memory in a superposition circuit, compares the bit data of each pixel data corresponding to a preset boundary color bit, and compares the bit data. When the data are the same, it is characterized in that at least one pixel data is changed to identifiable pixel data.

According to a second aspect of the overlay display device, the comparing means according to the first aspect includes a determining means for obtaining an exclusive OR of bit data corresponding to boundary color bits of each pixel data, And a color changing unit for changing the pixel data based on the result of the judging unit. Furthermore, the overlay display device according to claim 3 is
One of the plurality of color image data is cursor data for 8-color display, and the comparison means generates cursor data based on a value obtained by inverting bit data corresponding to a boundary color bit of the color image data. There is.

[0007]

For example, in a superposition display device in which pixel data is sequentially read from a plurality of image memories that store color image data in which one pixel data is composed of a plurality of bits, and each pixel data is superposed and output in a superposition circuit. The comparing means determines whether or not both bit data corresponding to a preset boundary color bit of each pixel data are equal, and when the both bit data are different, the pixel data overlapping each other are not the same color or similar color. It is determined that each pixel data is superposed as it is, and when both bit data are equal, it is determined that both pixel data have the same color or similar colors, and it is difficult to identify, and at least one pixel data is identified from another image. By changing to possible pixel data, each image to be displayed in a superimposed manner is displayed in a distinguishable manner.

Further, as a comparing means, a judging means for taking an exclusive OR of bit data corresponding to the boundary color bit of each pixel data, and at least one pixel data based on the result of the exclusive OR from the judging means. Is changed to pixel data that can be distinguished from other images, so that the superimposed image is displayed so as to be distinguishable from the lower image. Furthermore, one of the plurality of color image data is used as cursor data for 8-color display,
The comparison means inverts the bit data corresponding to the boundary color bit of the pixel data of the color image data and generates the cursor data based on the inverted bit data, so that the cursor and the image are displayed in a distinguishable manner.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of the present invention, and this embodiment describes a case where two images are displayed in a superimposed manner. In the figure, 1 is
The drawing processor is connected to the overlay display device 3 via the bus 2.

The overlay display device 3 inputs the color image data from the drawing processor 1 via the bus 2, and according to a predetermined control, for example, the color image data of the lower side image is stored in the image memory 5L. The color image data of the superimposed image to be superimposed on the side image is stored in the image memory 5U. The color image data is, for example, R,
One pixel data is composed of RGB signals each consisting of G, B, and 3 bits each for 9 bits in total, and color image data composed of this pixel data is stored in an image memory composed of 9 bitmap memories, each bit being 1 bit. It is stored corresponding to one bitmap memory.

The pixel data stored in the image memories 5L and 5U are sequentially read by the display control circuit 7,
The pixel data DL from the image memory 5L is supplied to the superposing circuit 11 and the pixel data DU from the image memory 5U.
Is output to the look-up table 9 as a comparison means. The lookup table 9 includes a drawing processor 1
From the pixel data DL output to the superimposing circuit 11, the boundary color bit data BL corresponding to the boundary color bit information BL and the image memory 5U are input. Of the pixel data DU, the boundary color bit data BU of the pixel data DU corresponding to the boundary color bit is obtained based on the boundary color bit information, and whether the boundary color bit data BU and the boundary color bit data BL are equal to each other or not. To determine.

For example, when the boundary color bit is set to the most significant bit g1 of the G (green) signal, that is, the intermediate color of the G (green) signal, and the boundary color bit data BL and BU are both "0". , The G signals (g1 to g3) of the superimposed image are set to all bits “1”, that is, a color brighter than the intermediate color of the G (green) signal, and the boundary color bit data BL and BU are set.
Are both "1", the G signal of the superimposed image is changed to all bits "0", that is, a color darker than the intermediate color of the G (green) signal, and the changed pixel data is output pixel data DU '. Is output to the superposition circuit 11.

In the superposing circuit 11, the image memory 5L
Input pixel data DL from the lookup table 9 and the output pixel data DU ′ from the lookup table 9
U'is superposed on the pixel data DL, converted into an analog signal, and output to the video control circuit 12a of the color CRT display 12. Then, the video control circuit 12a converts it into a video signal and displays it on the screen of the color CRT display 12.

Next, the operation of the first embodiment will be described.
Now, one pixel data of color image data is converted into, for example, FIG.
As shown in FIG. 3, it is assumed that each of the three bits is composed of RGB in order of 9 bits in total, and two images having the same structure are displayed in a superimposed manner. First, the drawing processor 1 stores the color image data of the lower image in the image memory 5L and the color image data of the superimposed image in the image memory 5U under predetermined control via the bus 2, for example.

Further, the drawing processor 1 outputs boundary color bit information and pixel data setting information to the look-up table 9. In the look-up table 9, for example, the boundary color bit is the highest order of the G (green) signal. When the bit g1 is set and the boundary color bit data BL and BU are both “0”, the G signals (g1 to g3) of the superimposed image are set to all bits “1” and the boundary color bit data BL and BU are set.
If both are "1", the G signal of the superimposed image is set to all bits "0".

Then, the pixel data DL and DU stored in advance in the image memories 5L and 5U are sequentially read by the display control circuit 7 and the pixel data DL are output to the superimposing circuit 11, and the look-up table 9 superimposes them. The boundary color bit data BL corresponding to the boundary color bit from the pixel data DL output to the circuit 11 and the image memory 5
The pixel data DU read from U is input.

Next, for example, pixel data DL formed from RGB components is "000""001""00".
0 ", that is," dark green ", and the pixel data DU
Is “000” “010” “000”, that is, “slightly dark green”, the pixel data DL is composed of the most significant bit on the left in the order of RGB.
Boundary color bit data BL of is the most significant bit g of the G signal
The bit data corresponds to 1, that is, "0".

The look-up table 9 determines whether or not these are equal based on the boundary color bit data BL and BU. At this time, since the boundary color bit data BU of the pixel data DU is the bit data corresponding to the most significant bit g1 of the G signal of the pixel data DU, it becomes "0", and both the boundary color bit data BL and BU are ". Since it is 0 ″, it is determined that the pixel data DL and DU are approximate colors having the same color but slightly different in brightness, and the G signals (g1 to g3) of the pixel data DU of the superimposed image are converted into pixel data of the pixel data. Based on the setting information, "111" is set and the output pixel data DU 'is set to "000", "111", "00".
0 ", that is," bright green "as the superposition circuit 1
Output to 1.

In the superposing circuit 11, the output pixel data DU 'and the pixel data DL are superposed on each other to form a color CRT.
It is output to the video control circuit 12a of the display 12 and converted into a video signal by the video control circuit 12a, and the color C
It is displayed on the RT display 12. As a result, on the color CRT display 12, the lower image is displayed with low brightness and the superimposed image is displayed with high brightness, and it is possible to distinguish between the two.

Further, the pixel data DL is "000""1".
01 "" 000 ", that is," slightly green ", and the pixel data DU is" 000 "" 110 "" 00.
0 ”, that is,“ a fairly bright green ”,
The boundary color bit data BL is “1”, the boundary color bit data BU is “1”, and both the boundary color bit data BL and BU are “1”. And the G signal (g1 to g) of the pixel data DU is determined based on the setting information of the pixel data.
3) is set to "000", and the output pixel data DU 'is output to the superposition circuit 11 as "000""000""000", that is, "black".

Predetermined processing is performed in the superimposing circuit 11, and the color CRT display 12 displays the lower image in high brightness and the superimposing image in "black", so that they can be distinguished from each other. It will be possible. Furthermore, pixel data D
L is “000” “001” “000”, that is,
It is "dark green" and the pixel data DU is "000""1".
In the case of 10 "" 000 ", that is," bright green ", the boundary color bit data BL is" 0 ", the boundary color bit data BU is" 1 ", and the boundary color bit data BL and BU are" 0 ". "And" 1 ", the pixel data DL
It is determined that the display colors of DU and DU are not approximate colors, the pixel data DU is not changed, and is output as it is to the superposition circuit 11 as the output pixel data DU ′.

Then, a predetermined process is performed in the superimposing circuit 11, and the color CRT display 12 displays the lower image in green with low brightness and the superimposed image in green with high brightness. Can be identified. Therefore,
When the images to be displayed in superimposition have the same color, it is possible to prevent the images from being difficult to see by superimposing the images of the same color by changing the superimposed image to the lower image and the target brightness.

In the first embodiment described above, the boundary color bit is set to the most significant bit of the G signal, but the most significant bit of the R signal or the B signal is set to the boundary color bit. It is also possible that R,
Pixel data D for the most significant bits of G and B respectively
It is also possible to compare L and DU, and if the most significant bits are equal, set the corresponding signal of the superimposed image to all bits "0" or "1". Also,
It is also possible to set the upper 2 bits or more of each signal as the boundary color bit.

Further, in the first embodiment described above, the case where two images are displayed in a superimposed manner has been described, but the present invention is not limited to this, and three or more images can be distinguished when they are approximate colors. It is also possible to superimpose and display each image in a distinguishable manner by changing to possible pixel data. Furthermore, in the first embodiment described above, the case where the pixel data of the superposed image is changed has been described, but it is also possible to change the pixel data of the lower image, and in the superposition circuit 11, the pixels that are not changed are changed. In the data,
By superposing the changed pixel data, it is possible to change any pixel data of the lower image and the superposed image.

Next, a second embodiment of the present invention will be described based on a block diagram (FIG. 3) showing its schematic configuration. In the second embodiment, the look-up table 9 is used as the comparing means in the first embodiment, but the exclusive OR of bit data corresponding to the boundary color bit of the superimposed image and the lower image is calculated. The comparison circuit 14 as the determination means having the exclusive OR function and the color change circuit 1 as the color change means.
5 and 5 are used.

The overlay display device 3 receives the pixel data from the drawing processor 1 via the bus 2 and, for example, pixel data of the lower image is stored in the image memory 5L according to a predetermined control. The pixel data is stored in the image memory 5U. The pixel data DL and DU are, for example, R, G, B and 3 bits each, for a total of 9 as in the first embodiment.
One pixel data is composed of RGB signals composed of bits, and the color image data composed of this pixel data is stored in an image memory composed of nine bitmap memories, and each bit is stored in one bitmap memory.

The color image data stored in the image memories 5L and 5U are sequentially read by the display control circuit 7, and the pixel data DL from the image memory 5L is transferred to the superposing circuit 11 to the pixels from the image memory 5U. Data DU
Is output to the color changing circuit 15. The comparison circuit 14 inputs the boundary color bit data BL, BU corresponding to the boundary color bits from the pixel data DL and DU output to the superposition circuit 11 and the color changing circuit 15, and inputs the boundary color bit data BL, It has an exclusive OR function for taking an exclusive OR with respect to BU, obtains the exclusive OR of the boundary color bit data BL and BU, and outputs the result to the color changing circuit 15. FIG. 4 shows the truth value of the exclusive OR of the comparison circuit 14.

The color changing circuit 15 receives the pixel data DU from the image memory 5U, the comparison result from the comparing circuit 14 and the color changing signal S from the color changing function setting register 16. The color change function setting register 16 receives the color change function setting command information from the drawing processor 1 and, when the color change function setting command is input, sends the color change signal S to the color change circuit 1.
Output to 5.

Then, in the color changing circuit 15, when the color changing signal S is inputted, the color changing function is activated and the comparing circuit 14
When the comparison result is "0", the pixel data DU is changed to the preset pixel data based on the result of the exclusive OR with the boundary color bit data BL and BU from It outputs to the matching circuit 11.

When the comparison result is "1", the pixel data DU is output as it is to the superposition circuit 11 as the output pixel data DU '. Then, in the superposing circuit 11, the pixel data DL from the image memory 5L and the output pixel data DU ′ from the color changing circuit 15 are input,
The output pixel data DU ′ is superimposed on the pixel data DU and converted into an analog signal, and the color CRT display 12 is displayed.
To the video control circuit 12a. Then, the video control circuit 12a converts it into a video signal and displays it on the screen of the color CRT display 12.

Therefore, for example, pixel data is converted into RGB.
It is assumed that two images formed of 3 bits each in the order of 9 bits in total are superimposed and displayed, and the boundary color bit is the most significant bit of the G (green) signal. Then, when the result of the exclusive OR in the comparison circuit 14 is "0", it is assumed that the G signal of the superimposed image is set to all bits to the inverted value of the bit data corresponding to the boundary color bit.

In this case, the color changing circuit 15 is set in advance so that all the bits of the G signal of the superposed image are set to the inverted value of the bit data corresponding to the boundary color bit as the setting information of the pixel data. deep. First, the drawing processor 1 stores the color image data of the lower image in the image memory 5L and the color image data of the superimposed image in the image memory 5U under predetermined control via the bus 2, for example.

Then, the drawing processor 1 outputs a color change function setting command in advance, and the color change function setting register 16
Outputs the color change signal S to the color change circuit 15 to enable the color change function. Next, the display control circuit 7 sequentially reads the pixel data DL of the stored lower image from the image memory 5L and the pixel data DU of the superimposed image from the image memory 5U, respectively, and outputs the pixel data DL from the image memory 5L. To the superposition circuit 11,
Further, the pixel data DU from the image memory 5U is output to the color changing circuit 15. In the comparison circuit 14, the boundary color bit data BL corresponding to the boundary color bit from the pixel data DL output to the superposition circuit 11 and the boundary corresponding to the boundary color bit data from the pixel data DU output to the color changing circuit 15. Input the color bit data BU and the exclusive OR of the input boundary color bit data BL and BU,
The result is output to the color changing circuit 15.

For example, the pixel data DL is "000".
“011” “000”, that is, “slightly dark green”, and the pixel data DU is “000” “001” “00”.
In the case of "0", that is, "very dark green", the G signal of the pixel data DL is "011", and the most significant bit is "0", so the boundary color bit data BL of the pixel data DL is Becomes "0", and the pixel data DU
G signal of "001" is "001" and its most significant bit is
Since it is “0”, the boundary color bit data BU of the pixel data DU becomes “0”, and both of the boundary color bit data are
Since it is “0”, the result of the exclusive OR from the comparison circuit 14 becomes “0” from FIG. 4, and the color change circuit 15 inverts the boundary color bit data “0” of the pixel data DU, Set this to all bits of G signal and set to “111”
And output pixel data DU ′ is “000” “111”
It is output to the superposition circuit 11 as “000”, that is, “bright green”.

In the superposing circuit 11, the output pixel data DU 'is superposed on the pixel data DL, converted into an analog signal, and output to the video control circuit 12a of the color CRT display 12. Then, the video control circuit 12a
Converted to video signal with and color CRT display 12
Displayed on the screen. This allows color CRT
On the display 12, the image on the lower side is displayed as low-intensity green and the superimposed image is displayed as high-intensity green, and both can be distinguished.

Further, the pixel data DL is "000""1".
10 "" 000 ", that is," very bright green ", and when the pixel data DU is" 000 "," 101 "" 000 ", that is," slightly bright green ", the boundary color bit of the pixel data DL Data BL is “1”, pixel data D
Since the boundary color bit data BU of U is "1" and both of the boundary color bit data are "1", the result of the exclusive OR from the comparison circuit 14 is "0" from FIG.
In the color changing circuit 15, the boundary color bit data “1” of the pixel data DU is inverted, all bits are set to G signal to be “000”, and the output pixel data DU ′ is set to “00”.
It is output to the superposition circuit 11 as 0 "" 000 "" 000 ", that is," black ".

Then, a predetermined process is performed in the superposing circuit 11, and the color CRT display 12 displays the lower image in high brightness green and the superposed image in "black". Can be identified. In addition, the pixel data DL is “000” “001” “000”, that is,
It is "dark green" and the pixel data DU is "000""1".
In the case of 10 "" 000 ", that is," bright green ", the boundary color bit data BL is" 0 ", the boundary color bit data BU is" 1 ", and the boundary color bit data is
Since they are “0” and “1”, the exclusive OR in the comparison circuit 14 is “1” from FIG. 4, and in the color changing circuit 15,
The pixel data DU is directly output to the superposition circuit 11 as the output pixel data DU ′ without being changed.

In the superposing circuit 11, the output pixel data DU 'is superposed on the pixel data DL, converted into an analog signal, and output to the video control circuit 12a of the color CRT display 12. Then, the video control circuit 12a
Converted to video signal with and color CRT display 12
Displayed on the screen. Thus, when the images to be superimposed and displayed have the same color, the superimposed image is changed to the target image and the lower image to prevent the images of the similar color from being difficult to see. be able to.

In the second embodiment, the color changing function setting register 16 is used to activate the color changing function of the color changing circuit 15. Therefore, activation / stop of the color changing function is arbitrarily set. can do. Also,
Although the boundary color bit is set to the most significant bit of the G signal in the second embodiment, the most significant bit of the R signal or the B signal can be set to the boundary color bit, and It is also possible to set the most significant bit of each R, G, B signal as a boundary color bit. Further, not limited to the most significant bit, it is possible to arbitrarily set the upper 2 bits or more.

Further, in the second embodiment, the value obtained by inverting the boundary color bit data is set as the G signal. However, if it is a color tone that shows a difference in color tone from other pixel data, it is set arbitrarily. be able to. Furthermore, in the second embodiment, the case where the pixel data of the superposed image is changed has been described, but the pixel data of the lower image can be changed, and the superposing circuit 11 does not change the pixel data. By superposing the changed pixel data on the pixel data, it is possible to change any pixel data in the lower image and the superposed image.

Next, a third embodiment of the present invention will be described based on a block diagram (FIG. 5) showing its schematic configuration. Third
The embodiment describes a case where the cursor data is superimposed on the color image data and displayed. The overlay display device 3 inputs the color image data from the drawing processor 1 via the bus 2, and stores the color image data in the image memory 5L and the cursor pattern in the cursor pattern memory 18 according to a predetermined control. This color image data constitutes, for example, 1 pixel data by an RGB signal consisting of R, G, B, and 3 bits each for a total of 9 bits.
The color pixel data composed of this pixel data is stored in the image memory 5L composed of nine bitmap memories, each bit corresponding to one bitmap memory.

The display color information of the cursor is transmitted from the drawing processor 1 and input to the cursor color setting register 19 via the bus 2. The cursor color setting register 19
Each of R and B is composed of 1 bit, that is, 2 bits in total, and outputs the cursor color data DC to the cursor overlay circuit 21 based on the cursor color information input from the drawing processor 1.

The color image data stored in the image memory 5L is sequentially read by the display control circuit 7 pixel by pixel, and the pixel data DL from the image memory 5L is read.
Is output to the cursor overlay circuit 21. Also,
Pixel data D output to the cursor overlay circuit 21
Boundary color bit data BL corresponding to a preset boundary color bit of L is output to the cursor overlay circuit 21 via the inverter 20 and the cursor overlay circuit 2
1 inputs 2-bit cursor color data DC of the R and B signals output from the cursor color setting register 19,
The boundary color bit data BL input via the inverter 20 is set as the G signal of the cursor color signal, and R, G, and B are set to 1 each.
A cursor color signal that can display 8 colors of 3 bits in total is generated.

Then, cursor data is generated based on the cursor pattern CP from the cursor pattern memory 18 and the generated cursor color signal, the cursor data is superimposed on the pixel data DL, and converted into an analog signal. Video control circuit 1 of color CRT display 12
2a. Then, it is converted into a video signal by the video control circuit 12a and displayed on the screen of the color CRT display 12.

Therefore, for example, it is assumed that the color image data composed of pixel data formed of 3 bits each in the order of RGB and a total of 9 bits are superimposed on the cursor data, and the boundary color bit is the most significant bit of the G signal. And
First, the color image data DL and the cursor pattern data CP are stored in the image memory 5L from the drawing processor 1 via the bus 2 under predetermined control.

Then, the display control circuit 7 sequentially reads the pixel data DL from the image memory 5L and outputs it to the cursor superposing circuit 21. Cursor overlay circuit 2
In 1, the boundary color bit data B corresponding to the boundary color bit
A value obtained by inverting L and a value obtained by inputting the cursor color data DC composed of R and B signals formed of 2 bits from the cursor color setting register 19 and inverting the cursor color data DC and the boundary color bit data BL Originally, an RGB signal of 3 bits is formed, cursor data is formed by the cursor pattern CP and the cursor color signal input from the cursor pattern memory 18 as a cursor color signal, and the cursor data is formed in the pixel data DL. It outputs the video data to the video control circuit 12a of the color CRT display 12 in a superimposed manner. Then, the video control circuit 12a converts it into a video signal and displays it on the screen of the color CRT display 12.

Therefore, for example, the pixel data DL is
In the case of "000", "110" and "000", that is, "very bright green", if the boundary color bit is the most significant bit of the G signal, the boundary color bit data becomes "1", and the cursor is overlaid. In the circuit 21, the data “0” is input via the inverter 20. And, for example,
Cursor color data D from the cursor color setting register 19
If “11” is input as C, “101” is generated as a cursor color signal based on these data, and cursor data is generated based on this cursor color signal and the cursor pattern CP. Color image data is color CRT based on the pixel data DL and the cursor data.
Output from the video control circuit 12a of the display 12.
Then, the video control circuit 12a converts it into a video signal,
It is displayed on the screen of the color CRT display 12.

In this case, the pixel data DL is "bright green".
On the other hand, the cursor becomes "purple", and even when the color image data and the cursor are superimposed and displayed,
These can be identified. Therefore, the third
According to the embodiment, since the value obtained by inverting the boundary color bit of the pixel data DL is set in the cursor data, the cursor color becomes a display color that is inconsistent with the pixel data DL, and even when these are superimposed and displayed, The cursor can be identified.

In the third embodiment, the case where the most significant bit of the G signal of the pixel data DL is inverted and set as the G signal of the cursor color signal has been described. It is also possible to set a value obtained by inverting the most significant bit as the cursor color data.

[0050]

As described above, according to the overlay display device of the present invention, the comparing means determines whether or not the bit data of the preset border color bits of the images to be overlay-displayed are equal, When these are equal to each other, one of the color image data to be superimposed and displayed is compared and changed by the comparing means, so that the images can be surely distinguished and displayed even in the case of the superimposed display.

Further, the comparing means includes a judging means for taking an exclusive OR of the bit data corresponding to the boundary color bits of the pixel data, and a color changing means for changing the pixel data based on the result of the judging means. With the provision, it is possible to surely distinguish and display the images even when the images are superimposed and displayed. Further, by generating the color information of the cursor based on the inverted value of the bit data of the boundary color bit of the color image data, the cursor can be displayed in a distinguishable manner even when the color image data and the cursor data are superimposed and displayed. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the operation of the first embodiment.

FIG. 3 is a block diagram showing a schematic configuration of a second embodiment of the present invention.

FIG. 4 is a truth table of exclusive OR of boundary color bit data BL and BU.

FIG. 5 is a block diagram showing a schematic configuration of a third embodiment of the present invention.

[Explanation of symbols]

 5L, 5U Image memory 9 Look-up table 11 Overlay circuit 14 Comparison circuit 15 Color change circuit 19 Cursor color setting register 20 Inverter 21 Cursor overlay circuit DL, DU Pixel data BL, BU Border color bit data

Claims (3)

[Claims] 1. A superposition method in which pixel data is sequentially read from a plurality of image memories that store color image data in which one pixel data is composed of a plurality of bits, and the pixel data read from each image memory in a superposition circuit is superimposed and output. The matching display device further includes a comparing unit that compares bit data of each pixel data corresponding to a preset boundary color bit and, when the bit data are equal, changes at least one pixel data into identifiable pixel data. An overlay display device characterized by the above. 2. The comparing means comprises a judging means for taking an exclusive OR of bit data corresponding to boundary color bits of each pixel data, and a color changing means for changing the pixel data based on the result of the judging means. 1. The method according to claim 1, further comprising:
The overlay display device described. 3. One of the plurality of color image data is 8
2. The overlay display device according to claim 1, wherein the cursor data is color display data, and the comparison means generates cursor data based on a value obtained by inverting bit data corresponding to a boundary color bit of color image data.