JPS63301991A - Display circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a display circuit.

[Summary of the invention]

The present invention improves color display capability in a display circuit for computer graphics, etc. by mapping and holding display data distributed according to predetermined rules.

(Prior Art) In computer graphics, it is generally considered that 256 colors (-28) per pixel is sufficient for color display capability.In other words, it is sufficient to allocate 8 bits to each pixel. .

However, recently there has been a demand for processing and displaying natural images, such as images captured with a video camera.
In this case, the ability to display 256 colors per pixel is insufficient.

However, in computer graphics,
It has a display capacity of about 2000 pixels x 000 pixels, so if you increase the color display capacity per pixel,
The display memory size becomes too large. For example, if 8 bits are assigned to each of red, green, and blue in one pixel, 24 bits are required per pixel, so the total is 24 bits x 2000 pixels x 000 pixels = 96
The size of the image is 000,000 bits H11.4 megabytes, which means that it takes a lot of time to process the image, or even if you use a hard disk drive, you can only store (save) a small number of images. However, it becomes impractical.

Therefore, a method has been considered in which the number of bits per pixel is set at 8 bits, but the color display capability is expanded by using a color look-up table.

FIG. 6 shows an example, (11 is a display memory,
In this memo (January 1), image display data DATA is taken out from addresses corresponding to horizontal scanning and vertical scanning of a color picture tube (not shown) in synchronization with clock CK. In this case, for example, as shown in FIG. 7, the size of data DATA for one pixel (9) is 8 bits, and the 8 bits are bits bv, b6...
Red display bit) bs~b2... Green display bit b1. bo: Assigned for displaying blue color. In other words, data DATA includes bits rbv, b6J, rbs~b2J, rb
x and bo J indicate the red, green, and blue levels (color saturation) of the corresponding pixel, respectively.

In addition, (21) to (23) are color, look, amplifier,
The mapping circuit for the table, in this example a memory, in which memories (21) and (23) each have 4 addresses, memory (22) has 16 addresses, and all memories (21) to (23) ) has a capacity of 8 bits per address, and each address stores data corresponding to the color desired to be displayed.

Furthermore, (31) to (33) are 8-bit lunches, (4
1) to (43) are 8-bit D/A converters.

Then, when the data DATA of a certain pixel is taken out from the memo (January 1), the red bits bv and be are supplied to the memory (21) as its address signal, and the corresponding address (the value indicated by bits b7 and b6) is supplied to the memory (21). address)
8-bit data DATR is taken out from the output, and this data DATR is launched into a latch (31) by a clock CK, and then supplied to a D/A converter (41) where it is converted into an analog red signal R.

Similarly, bits b5 to b2 for green color and bins bl and bo for blue color of data DATA are memories (22).

(23) as their address signals and 8-bit data DATG, respectively, from the corresponding address.
DATB is retrieved and these data DATG, D
ATB through 7chi (23) and (33)
/A converters (42) and (43) to generate analog green signal G and blue signal B.

These signals R, G, and B are then supplied to the color picture tube, so that a color image corresponding to the data DATA in the memory (1) is displayed.

In this case, the data DAT^, which is the address signal of the memories (21) to (23), can take on 28=256 values, and the output data DATR-DATB of the memories (21) to (23) are all There are 24 bits and 2
24=16777216 types of values can be taken, so 256 colors out of 16777216 colors can be displayed simultaneously.

In this way, by using the color look amplifier table, many hues and gradations (densities) can be expressed even if the capacity of the display memo (January 1) is small, and a colorful image can be displayed.

[Problem that the invention seeks to solve]

However, in the above circuit, only 256 colors out of 16777216 colors are selected and these 256 colors are displayed at the same time, which lacks a variety of colors for natural images, and it is difficult to achieve naturalness in color gloss. Sometimes it's missing. For example, when displaying a shiny fruit, only 2 bits are assigned to red and blue, and there are 4 gradations, so quantization becomes noticeable and color changes become striped.

Furthermore, considering the colors red, green, and blue, only 8 bits/3H2, 7 bits are allocated on average, resulting in a lack of gradation and a decrease in resolution.
Significant deterioration in image quality.

This invention attempts to solve these problems.

[Means for solving problems]

The present invention provides a display circuit that retrieves display data for each pixel from a display memory and performs mapping and D/A conversion on the retrieved display data to obtain three primary color signals of a color image. Among the three primary colors and brightness, data is defined as the color or brightness that has the smallest maximum error from the three more primary colors and brightness, and is data that has an identification code indicating that color or brightness, and the above The display circuit is configured to hold the display data retrieved from the display memory until the next display data of the same color or brightness is retrieved from the display memory according to the identification code.

[Effect]

Natural images are displayed without problems with gradation or resolution.

〔Example〕

In FIG. 1, the display memory (1) has a capacity equal to that described above, and image display data DATA is taken out from addresses corresponding to the horizontal scanning and vertical scanning of the color picture tube in synchronization with the clock CK.

In this case, the data DATA for one pixel (9) is 8 bits as described above, but this data DATA is
For example, the data is compressed according to the flowchart shown in FIG. 2, and has a format shown in FIG. 3, for example.

That is, in FIG. 2, R1, Gi, and Bi are the original data before compression, such as data captured by a video camera, and the red and green colors of the first pixel (9) on one screen. .

This is digital data that indicates the blue level in 8 bits. Furthermore, the value RX is the data RixBi of a certain pixel.
When the data R3 satisfies a predetermined condition,
be equivalent to. The same applies to the values * and B*.

Then, in step (101), R' = 0.3Rt +0.59G1 +0.
11BIG'=R', B'=R', i=1 are set, and then in step (102), the luminance data Y1 of the first pixel is changed from data R3xBl to Yi = 0.3Ri +0.59Gi +0. 11
It is calculated by Bi, and ΔR=IRi −R' 1 ΔG= lGi −GX 1 ΔB= l Bi −B' 1 ΔYr= IYi −Ri l ΔYg = l Yi −Gi 1ΔYb = l
Yi − Bi l is calculated.

Therefore, the values ΔR to ΔB represent the errors between the data Ri to Bi and the data RH and BX, and the values ΔYr to ΔYb represent the errors between the data Yi and the data Ri to B1, respectively. .

Then, in step (103), i, the larger error between the errors ΔG and ΔB is set as ΔB11, the larger error between the errors ΔR and ΔB is set as the error ΔT, iii. Among the errors ΔR and ΔG, the larger error is the error ΔU.iv Among the errors ΔYr to ΔYb, the largest error is the error Δ
Then, in step (104), the errors ΔS to Δ■ are compared to determine the smallest error among the errors ΔS to O ΔV.

In this case, among the errors ΔS to ΔV, for example, the value S
If is the minimum (ΔB<ΔT, ΔS<ΔU, ΔS<Δ■), this means that even the larger of the errors ΔG and ΔB is smaller than the other errors in step (103). It means. Therefore, the data Gi+Bi at this time can be replaced by the data aH, BH, and the green and blue data Gl of the first pixel,
It is no longer necessary to prepare Bi in the memo January 1). Furthermore, this allows the red data R1 of the i-th pixel to be prepared in the memo (January 1), and it is only necessary to update the data RN to the data Ri.

Further, the same processing can be performed when the errors ΔT to Δ■ are the minimum.

Therefore, when the error ΔS is the minimum, step (105
), R'=R3 and data Ri is 8
Bit data (original data) is converted to 6-bit data (compressed data) Re, and as shown in Figure 3, an identification code "oo" is placed above the data Re to indicate that it is red data. ” is added, and the data Rc
The total number of bits is 8 bits. Therefore, data Rc has the upper two bits b7. The identification code “00” indicates that bc is red data, and the remaining 6 bits b
5 to bo have information on the red gradation of the first pixel (9).

Also, at this time, 6 bits b5 to bo of data Rc are
For example, as shown in FIG. 4, 6 bits are assigned to the effective interval of the frequency distribution of the original data. Therefore, the data Rc has a sufficient quantization level even if only the 6 bits b5 to bo have gradation information.

Further, when the error ΔT is the minimum in step (104), G0=Gi is set in step (106), and data Gi is processed in the same manner as data Ri in step (105) to become data Gc. However, in data Gc, as shown in FIG. 3, the upper two bits bv.

bG is the identification code “01”, and the remaining 6 bits bε~
bo is assumed to be gradation information.

Further, when the error ΔU is the minimum in step (104), BM=Bi is set in step (107), and data Bi is processed in the same manner as data Ri in step (105) to become data Bc.

However, in data Be, the upper two bits bv, b
s is set as the identification code "10", and the remaining 6 bits b5 to b
o is density information.

Furthermore, when the error Δ■ is the minimum in step (103), in step (108), R0=Ri,
G' = Gi + B' = Bi, and data Yi is processed in the same way as data Ri in step (105) to become data Yc.

However, in data Yc, the upper two bits are bv.

bG is the identification code “11”, and the remaining 6 bits b5~
bo is assumed to be gradation information.

Then, in step (109), the data Rc + Gc, Be or Yc formed in any one of steps (105) to (10B) is stored in a storage means, for example, a memo 1.
The data of the i-th pixel (9) is stored as data DATA at the i-th address of month 1).

Then, in step (110), the value i is incremented by "1" and the next pixel (9) is targeted for processing, and in step (111), whether or not the above processing has been performed for all pixels (9)? is determined, and if there is an unprocessed pixel (9), step (102)
The subsequent processing is repeated.

Therefore, for each pixel (9), the memory (11) stores, as data DATA, information on the gradation of the color or luminance that has the largest level change with respect to the previous pixel (9).

Furthermore, the memories (21) to (23) for color look amplifier tables have 256 addresses, and each address has a capacity of 9 bits. In the memory (21), the upper two bits A7. of addresses A7 to Ao. The value of the identification code where As is red is ``00''
” or when the brightness identification code value becomes “11”,
A predetermined value is set so that the most significant bit D8 of the data D8 to Do becomes "1" and data at the level of the red component of the desired color is output as the lower bits D7 to Do (red data DATR). Data is stored. In other words, in memory (21), OOH~3F
Ds="1", Dv~Do-r red data DATRJ at address H and COH-FFH address (H indicates hexadecimal)
is stored.

In addition, in the memory (22), addresses A7 to A
o's top 2 pits) A? , AG is the green identification code value “
01" or the brightness identification code value "11", the most significant bit D8 of data D8 to Do becomes "1", and the data at the level of the green component of the color to be displayed is set to the lower bit. D7~D.

Predetermined data is stored so as to be output as (green data DATG). That is, memory (22)
, D8-1'', Dv~Do = r green data DA at addresses 40H to 7FH and COH to FFH.
TGJ is stored. Furthermore, in the memory (23), the upper two bits Av, A of addresses A7 to Ao are
When s reaches the blue identification code value "10" or the brightness identification code value "11", the most significant bit D8 of data D8 to Do becomes "1", and the color you want to display is adjusted. The level data of the blue component is the lower bits D7 to Do.
So that it is output as (blue data DATB),
Predetermined data is stored. In other words, memory (
22), address 80H-BP)1 and C0H-
At address FFH, D*-"1", D? ~Do=rBlue data DATBJ is stored.

In addition, Co)l-FF11 of memories (21) to (23)
The same data is stored at addresses (21), (22), and (23).

In addition, the memory (21) for lunch (31) to (33)
) to (23) are supplied as latch enable signals.

According to such a configuration, the memory (from 11 to data DA
When TA is retrieved, this data DATA is stored in memory (
21) to (23) and some data DATR
~DATB, and this data DATR~DATB
is supplied to the latches (31) to (33).

And in this case, the data DATA from the memo January 1)
However, for example, if it is red data Rc, its upper two bits by and bs are “OO”, so only the most significant bit D8 of the output of memory (21) becomes “1”, and this bit D8 causes the data DATR to launch. (31), and therefore, the red signal R is taken out from the D/A converter (41).

In addition, at this time, the data DATA is stored in the memory (22)
.

Since it is also supplied to (23), memory (22)
.

Data DATG and DATB are also output from (23), but the upper bits of data DATA (rising bits b7.bε are “
00'', the most significant bits Da and D8 of the outputs of memories (22) and (23) will never become 11.
Therefore, data DATG and DATB are latched (3
2), (33) is not latched, and the data DATG and DATB when latched before that
will remain retained.

This state in the latch (31) is maintained until the next red data Rc is retrieved from the memory (1), i.e., until the change in gradation of red becomes larger than the change in gradation of other colors. .

Also, if the data DATA from the memo January 1) is green data Gc or blue data Be, the upper 2 bits b7. According to b, the most significant bit De of the output of the memory (22) or (23) becomes 1'', so the data DATG or DATB is launched into the latch (32) or (33), and the D/A converter (42)
) or from (43) green signal G or blue signal B
is taken out.

Furthermore, if the data DATA from the memo January 1) is the luminance data Yc, its upper two bits b, , b6 are “
11'', data DATR-DATB that are equal to each other are output from all memories (21) to (23), and all the most significant bits D8 to D8 become 1'', so the launches (31) to (33) are ) data DATR to DATB are latched at the same time, and the converter (
A signal R-B having luminance information (brightness information) is extracted from 41) to (43).

Therefore, for each pixel (9), the data DATA is red ~
It is determined by the identification code whether it is blue or brightness data. In other words, for each pixel (9), the color or brightness that has the largest gradation change from the previous pixel (9) is determined, and that change is determined. The data in the latches (31) to (33) are updated in accordance with the color or brightness that is the largest, and the signal R-B is taken out.

In this way, the three primary color signals R-B can be obtained, but in this case, according to the present invention, 6 bits are allocated to each of red to blue, so one color is expressed with 18 bits. Therefore, 2” = 2
Since 62,144 colors can be generated simultaneously, even natural images can be displayed with sufficient gradation, and natural and glossy colors can be projected.

In addition, priority is given to displaying colors with large gradation changes after the change, and the idea of brightness is also adopted.When the brightness change of the original data is large, signals R to B are changed to 18 in accordance with the identification code "11". Since the brightness of the display screen changes simultaneously in bits, extremely high resolution can be obtained.

Furthermore, since the concept of brightness is adopted, for example, the boundary between a black part and a white part will not be colored. That is, at the boundary between the black part and the white part, for example, as shown in FIG. 5, the red to blue data R1=Bi all change significantly at the same time. If the signals Yr to ΔYb and Δ■ are not adopted, the value ΔR9ΔG is determined in step (104).

The smallest of ΔB, e.g. ΔB〈ΔT, ΔS〈Δ
If U, the value ΔS is determined to be the minimum, and step (10
5), the data Rc is regarded as the data DATA of the i-th pixel (9), so when displaying, the data Rc of the i-th pixel (9) is
) for green and blue, for example (i
The level of the -1)th pixel (9) is set as the level, and the level of green is set as the level after the change. therefore,
In the i-th pixel (9), the red level is higher than the green and blue levels, so it is colored red. Then, the same thing occurs for the next (i+1)th pixel (9).

However, according to the present invention, since the idea of brightness is adopted and the signals ΔYr to ΔYb and ΔV are formed, the levels of the signals R to B at the i-th pixel (9) change simultaneously,
Therefore, it is not colored.

Moreover, only for color or brightness data with large gradation changes, an identification code indicating the color or brightness is added and used, so the capacity of the memory (11) does not increase. There is no need for a compression circuit, and it can be handled simply by mapping using memories (21) to (23).

Note that in the above, the upper bit bv of data DATA
, bs to latch enable signals for launches (31) to (33), if formed by an AND circuit and an inverter, memories (21) to (23) will be 1
The address may have a capacity of 8 bits. In that case, memory (21) to (23) and latch (31)
-(33) can be reversed.

Furthermore, in the above description, the data DATA is stored in the memory (1) in step (10B), but in reality, it is stored in the hard disk or other memory.
After completing the necessary processing, the data may be transferred to the memory (11).

Further, the processing shown in FIG. 2 can be realized by either software or hardware.

〔Effect of the invention〕

According to this invention, 6 bits are allocated to each of red to blue, so one color is expressed with 18 bits, so 218 = 262144.
Since colors can be generated simultaneously, even natural images can be displayed with sufficient gradation, and natural and glossy colors can be projected.

In addition, priority is given to displaying colors with large gradation changes after the change, and the idea of brightness is also adopted.When the brightness change of the original data is large, the signal R-B is set to 18 in accordance with the identification code "11". Since the brightness of the display screen changes simultaneously in bits, extremely high resolution can be obtained.

Furthermore, since the idea of brightness is adopted, for example, the border between a black part and a white part is not colored. The red to blue data Ri-=Bi all change significantly at the same time. If the signals Yr to ΔYb and ΔV are not adopted, the value ΔR9ΔG is set in step (104).

The smallest of ΔB, e.g. ΔB<ΔT, ΔS×Δ
If U, the value ΔS is determined to be the minimum, and step (10
5), the data Rc is regarded as the data DATA of the i-th pixel (9), so when displaying, the data Rc of the i-th pixel (9) is
) for green and blue, for example (i
The level of the -1)th pixel (9) is set as the level, and the level of green is set as the level after the change. therefore,
In the first pixel (9), the red level is greater than the green and blue levels, so it is colored red. Then, the same thing occurs for the next (i+1)th pixel (9).

However, according to this invention, since the idea of brightness is adopted and the signals ΔYr to ΔYb, Δ■ are formed, the levels of the signals R-B at the i-th pixel (91 change simultaneously,
Therefore, it is not colored.

Furthermore, since an identification code indicating the color or brightness is added and used only for color or brightness data with large gradation changes, the memo 1) does not have a large capacity. Furthermore, there is no need for a special color compression circuit, and the problem can be handled simply by mapping using memories (21) to (23).

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of the present invention, and FIGS. 2 to 7 are diagrams for explaining the same. (1) is display memory, (21) to (23) is mapping memory, (31) to (33) is lunch, (41) to
(43) is a D/A converter.

Claims (1)

[Scope of Claims] A display circuit that retrieves display data for each pixel from a display memory, and maps and D/A converts the retrieved display data to obtain three primary color signals of a color image. is data on the color or luminance that has the smallest maximum error from the previous three primary colors and luminance among the three primary colors and luminance, and is data that has an identification code indicating that color or luminance. , The above display data retrieved from the above display memory is
A display circuit configured to hold display data of the same color or brightness according to the identification code until the next display data of the same color or brightness is retrieved from the display memory.