JP3249452B2 - Digital gamma correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital gamma correction circuit for gamma correcting digital luminance data and digital density data according to gamma characteristics of LCDs, scanners, printers and the like.

[0002]

2. Description of the Related Art Conventionally, as a digital gamma correction circuit of this type, a conversion value corresponding to a gamma characteristic of an LCD, a scanner, a printer or the like is stored in a ROM in advance, and digital luminance data and digital density data before correction are addressed. A method of performing gamma correction by applying the correction value to a ROM, and dividing the digital luminance data and digital density data X before correction into a plurality of regions and calculating each region by a calculation circuit according to the following equation. How to do is known.

Y = AX + B, where Y is the output value, and A is the slope of the gamma correction polygonal line for each area.

[0004]

SUMMARY OF THE INVENTION However, ROM
In the method using the method, when the number of correction curves is increased, the number of ROMs is required, which causes a problem that the cost is increased and the circuit area is increased. Similarly, in the method using an arithmetic circuit, when the number of γ correction broken lines is increased, the circuit scale increases, and the processing time also increases.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is directed to a digital gamma correction circuit for obtaining digital output data by correcting digital input data based on a gamma correction broken line. Each break point position in the input data direction of the γ correction broken line is set as a fixed position, and it is possible to specify tilt data for each of a plurality of regions divided by the fixed position, and a plurality of tilt data from the specified tilt data and the fixed position. A break point calculation circuit that calculates each break point position in the output data direction of the γ-correction broken line for each area prior to input of input data; and a break point position in the output data direction calculated by the break point calculation circuit. And a real-time processing circuit for correcting input data in real time based on the specified tilt data and outputting corresponding output data. The positive circuit path is intended to solve the above problems.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a digital γ correction circuit according to the present invention, FIG. 2 is an explanatory diagram showing γ correction characteristics of the digital γ correction circuit of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing the processing, and FIG.
FIG. 5 is an explanatory diagram showing the processing of the to4 encoder, FIG. 5 is an explanatory diagram showing the processing of the flag encoder of FIG. 1, and FIG. 6 is an explanatory diagram showing the γ correction processing of the digital γ correction circuit of FIG.

The digital gamma correction circuit shown in FIG. 1 is, for example, as shown in FIG. 2, for correcting the gamma characteristic of an LCD, as shown in FIG. 2, digital luminance data X [9 of 10 bits (8 bits for integer part, 2 bits for decimal part). : 0] is divided into 12 regions, and 1
12-bit (8-bit integer part, 4-bit decimal part) correction data Y with two γ correction polygonal lines (slope A0 to A11)
[11: 0] shows a configuration for performing γ conversion. here,
In FIG. 2, an input value X is a break point X in the X direction shown below.
It is divided into 12 regions with 1 to X11 as a boundary. In addition, as shown below, “;”, which is divided into upper 5 bits, is for explaining a small area described later. In the X direction of the figure, a value in which the upper 5 bits are represented by a hexadecimal number (hex) is shown. It has been described.

X1 = 000000; 00000 (shown as “1”) X2 = 000000; 00000 (shown as “2”) X3 = 0100100; 00000 (shown as “4”) X4 = 010010; 00000 ( X6 = 011010; 00000 (illustrated "A") X6 = 01110; 00000 (illustrated "E") X7 = 10110; 00000, 000 (illustrated "16") X8 = 11010; 000, 00 ("1A" shown) X9 = 11100; 00000 ("1C" shown) X10 = 11110; 0000, 000 ("1E" shown) X11 = 11111; 00000, 00 ("1F" shown) That is, this area Each of the areas A0 and A1 has one slope so that the interval becomes finer in the bright part and the dark part, and becomes coarser in the halftone as follows. 2 areas for A3, 2 areas for slopes A4, A5, 4 areas for slope A6, 4 areas for slope A7, 2 areas for slopes A8, A9, 2 areas for slopes A10, A11 Contains one small region, and the width of this small region in the X direction is “1; 00”.
0000 ", that is," 8 ".

A0: “00000; 00000” to “00000; 111, 11” A1: “00001; 00000” to “00001; 111, 11” A2: “000010,000,000,” to “00010; 111,11 ""00011; 00000,00 "to"00011; 111,11 "A3:"00100; 00000,00 "to"00100; 111,11 "" 00101: 000000 "to"00101; 111,11 " A4: “00110; 00000,00” to “00110; 111,11” “00111; 000000” to “00111; 111,11” “01000; 000000” to “01000; 111,11” “01001” ; 00000,00 "to"01001; 111,11 "A5:"01010; 00000,00 ""01010;111,11""01011;00000,00" to "01011;111,11""01100;00000,00" to "01100;111,11""01101;00000,00" to "01101;111" , 11 "A6:"01110; 00000,00 "to"01110; 111,11 ""01111; 00000,00 "to"01111; 111,11 ""10000; 00000,00 "to"10000; 111,11 "“10001; 00000” to “10001; 111, 11” “10010; 00000” to “10010; 111, 11” “10011; 00000” to “10011; 111, 11” “10100; 000, 00 "to"10100; 111, 11 ""10101; 000000 "to" 10101 " 111, 11 "A7:"10110; 000000 "to"10110; 111, 11 ""10111; 000000 "to"10111; 111, 11 ""11000; 000000 "to"11000; 111, 11 "11001;00000,00" to "11001;111,11" A8: "11010;00000,00" to "11010;111,11""11011;00000,00" to "11011;111,11" A9 : “11100; 000000” to “11100; 111, 11” “11101; 000000” to “11101; 111, 11” A10: “11110; 000000” to “11110; 111, 11” A11: “11111; 00000,00” to “11111; 111,11” The break point calculation unit 1 shown in FIG. The selector 13, the inclination data of the 12 regions of the operation unit of the not shown A0~
A11 is applied as 8-bit data AX [7: 0] consisting of a 3-bit integer part and a 5-bit decimal part, and is also supplied to the break point calculation unit 1 in advance at each of the boundary points X1 of the 12 regions.
To X11 are set.

The break point calculation unit 1 calculates the inclination data A0 to A11 and the boundary points X1 to X1 of the twelve areas.
1, 11 break point values Y in the Y direction shown in FIG.
1 to Y11 are calculated during the time of one screen (1V) of the LCD image, stored in the register 1a and continued from the first pixel of the next screen, and until the next inclination is set, the selector 14 is output. Here, since the input data is a video signal, the contents of the register 1a are rewritten during the vertical blanking period. These break point values Y1 to Y11
Are 10-bit data Y [9: 0] composed of an 8-bit integer part and a 2-bit decimal part.

Here, 8-bit gradient data AX [7:
0] is composed of a 3-bit integer part and a 5-bit decimal part as shown in FIG.
In the case of 1, the inclination data AX [7: 0] is "001, 0".
0000 ”, and when the slope is a decimal value = 2, the slope data AX [7: 0] is“ 010,0000 ”.
0 ", and when the slope is a decimal value = 1/2, the slope data AX [7: 0] is represented by" 000, 10000 ".

Therefore, the first break point value Y1 shown in FIG.
Can be obtained by multiplying the width of one small area by the slope A0 since the area having the slope A0 is composed of one small area. Since the width of the one small area is “1000” (“8”) as described above, multiplying the slope by “1000” means that the slope is determined by the 3-bit MSB.
It is determined by shifting to the side. Therefore, the inclination data A0 [7: 0] can be obtained by shifting the 3-bit MSB side to the MSB side (A0 << 3 in the figure) as shown in FIG. For example, slope = 2 (decimal) = 010,00000
In this case, if this is shifted to the MSB side by 3 bits, Y1 = 01000000,00, and the above-mentioned first boundary point X1 = 0000100
The value is twice 0000. Also, for example, slope = 1 /
If 2 (decimal) = 00000, 10000
Shifting to the B side by 3 bits gives Y1 = 000100,00, and the above-mentioned first boundary point X1 = 0000100
It becomes a value obtained by multiplying 0.00 by １ ／.

Similarly, Y2-Y1 is such that the area of inclination A1 is 1
Of the tilt data A1
[7: 0] can be obtained by shifting 3 bits to the MSB side, and the second boundary point Y2 can be obtained by adding the above Y1. Next, Y3-
In Y2, since the area of A2 is composed of two small areas, the slope data A2 [7: 0] is shifted to the 3-bit MSB side as described above, and this may be doubled, instead of doubled. One more bit shift may be required. That is, it can be obtained by shifting the inclination data A2 [7: 0] by 4 bits to the MSB side, and the third boundary point Y3 can be obtained by adding the above Y2.
Similarly, the above difference composed of two small areas can be obtained by shifting the gradient data AX [7: 0] by 4 bits to the MSB side, and is composed of four small areas. The difference is that the inclination data AX [7: 0] is shifted to the MSB side by 5 bits, and the difference composed of eight small areas is that the inclination data AX [7: 0] is 6 bits and the MSB It can be obtained by shifting to the side. However, the ninth bit or more of the integer part is treated as overflow, and when any of these bits is “1”, it is all 1s.

Returning to FIG. 1, 10-bit input data X
Of [9: 0], the upper 5 bits X [9: 5] are applied to the 5to4 encoder 11 and the flag encoder 12, and the lower 5 bits X [4: 0] are applied to the adder 15. 5to
4 encoder 11, as shown in FIG.
Based on [9: 5], the above 12 areas (tilt A
0 to A11), that is, a 4-bit gradient selection signal SEL3 to SEL0, which is decoded and output to the selectors 13 and 14.

Here, referring to FIG. 2, for example, the inclination A
The input data area of No. 4 is “00110; 000000”
("6" in the figure) to "01001; 111, 11" (immediately before "A" in the figure), so the upper 5 bits X [9: 5] of the input data are "00110" as shown in FIG. In the case of “00111”, “01000”, and “01001”, all the slope selection signals SEL3 to SEL0 are “010”
0 ".

The selector 13 receives the gradient selection signal SEL3
One of the slope data A0 to A11 A [7:
0], and this is converted to a broken line for γ correction Y = A * ΔX + B
Is output to the calculation unit 16 as the inclination A of In addition, the selector 14 calculates one of the break point values Y0 to Y11 calculated by the break point calculation unit 1 based on the inclination selection signals SEL3 to SEL0.
One of them is selected and output to the arithmetic unit 16 as a γ-correction polygonal line Y = A * ΔX + B.

As shown in FIG. 5, the flag encoder 12 outputs a signal indicating which of the twelve areas is a small area, that is, a 3-bit signal, based on the upper 5 bits X [9: 5]. The flag F [7: 5] is encoded and output to the adder 15. Here, referring to FIG. 2, for example, the area of the input data having the slope A4 is “00110; 00”.
0000 "(" 6 "in the figure) to"01001; 111,
11 ”(immediately before“ A ”in the figure).
As shown in FIG. 5, [7: 5] is “000” when the upper 5 bits X [9: 5] of the input data is “00110”: first small area “0011” when it is “00111”: second small When the area is “01000”, “010” is the third small area. When the area is “01001”, it is “011”: the fourth small area. 5 to 4 encoder 11 and flag encoder 12
Can be constituted by a logic circuit or a ROM.

The adder 15 sets the flag F [7: 5] to 8
The upper 3 bits of the bit data ΔX [7: 0] and the lower 5 bits of the 10-bit input data X [9: 0]
Bits X [4: 0] are set as 8-bit data ΔX [7: 0], which is the lower 5 bits of 8-bit data ΔX [7: 0], and are calculated as ΔX of γ correction broken line Y = A * ΔX + B Output to the unit 16. That is, this 8-bit data ΔX [7: 0] is a break point value X1 in the X direction with the previous area.
~ X11. Here, it can be easily understood that the adder 15 can be easily formed by an 8-bit bus or the like instead of the arithmetic unit.

The operation unit 16 is constituted by a product-sum operation unit.
The value ΔX [7: 0] from the X-direction break point values X1 to X11 with respect to the previous area calculated by the adder 15, the slope A [7: 0] selected by the selector 13, and the selector 1
4, a breakpoint value Y1 in the Y direction with the previous area selected by
Based on デ ー タ Y11 = B and the following equation Y = A * ΔX + B, 12-bit (8-bit integer part, 4-bit decimal part) γ-correction data is calculated and output to the LCD. Here, when the calculation unit 16 calculates the above equation, FIG.
As shown in the above, the ninth bit of the integer part of the operation result is treated as overflow, and in the case of “1”, all 12 bits are set to “1”. In addition, the value after the fifth decimal place is rounded down and output as 12 bits.

That is, in the above configuration, the break point calculation unit 1
When the inclination data A0 to A11 are input, the eleven break point values Y1 to Y11 in the Y direction are displayed on one screen (1V) of the LCD image.
And outputs it to the selector 14 continuously from the next screen onward. In contrast, the 5to4 encoder 11, the flag encoder 12, the selectors 13, 1
4. The adder 15 and the operation unit 16 perform processing on the input data in real time.

[0021]

As described above, according to the digital gamma correction circuit according to the present invention, the break point position in the input data direction of the gamma correction broken line is fixed, and the break point position calculation in the output data direction with a large amount of calculation is performed. Is performed prior to data input, real-time processing at the time of data input becomes faster, and the circuit scale can be reduced.

Further, the arithmetic processing can be simplified by selecting a plurality of inclinations and a plurality of breakpoint positions in the output data direction in accordance with predetermined upper bits of the input data. Further, a plurality of gradient data designated for each region are shifted for each bit according to the size of the region, and the shift result is added for each region, thereby obtaining γ.
Since the break point in the output data direction of the correction broken line is calculated, the calculation can be speeded up.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a digital gamma correction circuit according to the present invention.

FIG. 2 is an explanatory diagram showing γ correction characteristics of the digital γ correction circuit of FIG. 1;

FIG. 3 is an explanatory diagram illustrating a process of a break point calculation unit in FIG. 1;

FIG. 4 is an explanatory diagram showing processing of a 5to4 encoder in FIG. 1;

FIG. 5 is an explanatory diagram showing processing of the flag encoder of FIG. 1;

FIG. 6 is an explanatory diagram showing γ correction processing of the digital γ correction circuit of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Break point calculation part 11 5 to 4 encoder 12 Flag encoder 13, 14 Selector 15 Adder 16 Calculation part

Continued on the front page (72) Inventor Yusuke Tsutsui 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Hisao Uehara 2-5-5-1 Keihanhondori, Moriguchi-shi, Osaka Sanyo (56) References JP-A-4-355587 (JP, A) JP-A-8-214190 (JP, A) JP-A-4-33477 (JP, A) JP-A-5-244460 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G06T 5/00 100 H04N 1/407 H04N 5/202

Claims (4)

(57) [Claims] 1. A digital γ obtaining digital output data by correcting digital input data based on a γ correction broken line.
In the correction circuit, each break point position in the input data direction of the γ-correction broken line is set as a fixed position, and the tilt data can be designated for each of a plurality of regions divided by the fixed position. A break point calculation circuit for calculating each break point position in the output data direction of the γ-correction broken line for each of a plurality of regions from a fixed position prior to input of input data; and the output data direction calculated by the break point calculation circuit And a real-time processing circuit that outputs γ-corrected input data in real time based on each of the breakpoint positions and the designated inclination data, and outputs the corresponding output data. A first selection circuit for selecting one of a plurality of pieces of gradient data specified for each of the plurality of areas in accordance with a predetermined upper bit; Depending on the predetermined upper bits of data,
A second selection circuit for selecting one of a plurality of breakpoint positions in the output data direction calculated for each of the plurality of regions by the breakpoint calculation circuit; A calculating circuit for calculating a difference from the break point position in the input data direction to the input data; multiplying the slope data selected by the first selecting circuit by the difference calculated by the calculating circuit; An arithmetic circuit for adding the value of the breakpoint position selected by the second selection circuit and outputting the addition result as a γ correction value of the input data.
Is a video signal, and the break point calculation circuit
A digital gamma correction circuit for updating the operation content output during a vertical blanking period of a signal. 2. A digital γ obtaining digital output data by correcting digital input data based on a γ correction broken line.
In the correction circuit, each break point position in the input data direction of the γ-correction broken line is set as a fixed position, and the tilt data can be designated for each of a plurality of regions divided by the fixed position. A break point calculation circuit for calculating each break point position in the output data direction of the γ-correction broken line for each of a plurality of regions from a fixed position prior to input of input data; and the output data direction calculated by the break point calculation circuit A real-time processing circuit that outputs γ-correction input data in real time based on the respective breakpoint positions and the specified inclination data, and outputs corresponding output data,
The real-time processing circuit includes: a first selection circuit that selects one of a plurality of pieces of gradient data specified for each of the plurality of regions in accordance with a predetermined upper bit of the input data; A second selection circuit that selects one of a plurality of breakpoint positions in the output data direction calculated by the breakpoint calculation circuit for each of the plurality of regions in accordance with the upper bit, based on the input data, A calculating circuit for calculating a difference from the break point position in the input data direction in the area to which the input data belongs to the input data; multiplying the slope data selected by the first selecting circuit by the difference calculated by the calculating circuit; , The result of the multiplication and the second
Add the value of the break point position selected by the selection circuit of
An arithmetic circuit that outputs the addition result as a γ correction value of the input data, wherein the break point arithmetic circuit converts a plurality of pieces of inclination data specified for each of the plurality of areas according to the size of the area. A digital gamma correction circuit for calculating a break point position in the output data direction of a gamma correction polygonal line by adding a shift result for each area by shifting each bit. 3. A digital γ obtaining digital output data by correcting digital input data based on a γ correction broken line.
In the correction circuit, each break point position in the input data direction of the γ correction broken line is set in advance and divided into a plurality of regions, and a plurality of inclination data designated for each of the plurality of regions and the predetermined A broken point calculation circuit for calculating each broken point position in the output data direction of the gamma correction broken line based on each broken point position in the input data direction; and The first selection circuit for selecting one of the plurality of inclination data designated respectively, and the break point calculation circuit for each of the plurality of regions in accordance with a predetermined upper bit of the input data. A second selection circuit for selecting one of a plurality of breakpoint positions in the output data direction; and
A calculating circuit for calculating a difference from the break point position in the input data direction in the area to which the input data belongs to the input data; multiplying the slope data selected by the first selecting circuit by the difference calculated by the calculating circuit; An arithmetic circuit for adding the multiplication result and the value of the break point position selected by the second selection circuit, and outputting the addition result as a γ correction value of the input data. Is obtained by shifting a plurality of inclination data designated for each of the plurality of regions for each bit in accordance with the size of the region, and adding the shift result for each region.
A digital gamma correction circuit for calculating a broken point position of a correction broken line in the output data direction. Wherein said input data is a video signal, the break point arithmetic circuit, according to claim 2 or and updates the content of operation to be output to the vertical blanking period of the video signal
Digital γ correction circuit according to another 3.