JPH05297844A - Gamma correcting circuit of image display device - Google Patents

Abstract

PURPOSE:To speedily and easily generate a gamma correction curve for a CRT display. CONSTITUTION:Slide resistors 12 are provided corresponding to plural sample points constituting the gamma correction curve. Voltage values generated corresponding to the positions of the slide terminals of those slide resistors 12 are digitized to generate the gamma correction curve. Consequently, the outline of the gamma correction curve to be generated can be imaged from the respective slide terminal positions of the slide resistors and the generation of the gamma correction curve is speeded up and made easy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a γ correction device for an image display device, and more particularly to a γ correction device for converting input image data according to a preset γ correction curve and displaying an image by the converted data. is there.

[0002]

2. Description of the Related Art In an information processing apparatus, image data stored in a frame memory is displayed on a high resolution display (hereinafter referred to as C
Consider the case of displaying on RT). If the number of bits of each pixel of the image data in the frame memory is 12 bits, the range of values that can be taken by the data of each pixel is 0 to 4096. Here, when the CRT has a brightness of 0 to 255 gradations due to its performance, each pixel data of 0 to 4096 is converted to 8-bit data of 0 to 255 by using a lookup table,
After that, it is converted into an analog signal indicating the brightness level of black (0) to white (255) by D / A conversion and displayed on the CRT.

Now, when a pixel whose data is 0 is made black and a pixel whose data is 4096 is made to correspond to white, the conversion characteristics are as shown in FIG.

In this case, the pixel data (0 to 4096) is not always linearly converted into the brightness black (0) to white (255). This is because the brightness displayed on the CRT and the brightness displayed on the human eye do not have a linear correspondence relationship.

Therefore, when the image data is displayed on a CRT, it is necessary to convert the image data into an image having a light and shade distribution that matches the human visual sense, and the conversion curve at this time is called a "γ correction curve".

Conventionally, as the γ correction processing in an image display apparatus, some specific γ correction curve patterns are stored in the processing apparatus in advance, and an appropriate one is selected from these and the γ correction processing is performed. There is a method of processing. Also,
As another method, there is a method of numerically inputting some sample points forming the γ correction curve and using the values of the input sample points to create a γ correction curve by software to perform processing.

In the former method, that is, in the method of selecting from a plurality of γ correction curves stored in advance, there is no choice but to select from a γ correction curve having a limited pattern, and therefore the degree of freedom of the γ correction processing is small. There is a drawback.

In the latter method, that is, in the method of numerically inputting the sample points of the γ correction curve with a keyboard or the like, γ is used in the process of creating the γ correction curve by software.
It is difficult to grasp the outer shape of the correction curve (image of conversion characteristics), and there is a drawback that a processing step such as calculation of an input numerical value is required.

[0009]

It is an object of the present invention to easily input numerical values for each sample point constituting a γ correction curve and to obtain the resulting γ.
An object of the present invention is to provide a γ correction circuit of an image display device that allows the image of the correction curve to be easily grasped visually.

[0010]

According to the present invention, the input image data is converted in accordance with a preset .gamma. Correction curve, and the .gamma.
A plurality of correction circuits, each of which has a slide terminal which is provided corresponding to each of a plurality of sample points forming the γ correction curve and which can slide, and which generates a voltage value corresponding to the position of the slide terminal. A slide resistor, a curve generating means for approximately generating a γ correction curve by using respective generated voltage values of these slide resistors, and a means for converting the input image data according to the γ correction curve and displaying the image. It is possible to obtain a γ correction circuit characterized by including

[0011]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system block diagram of an embodiment of the present invention. The input unit 1 inputs each numerical value of a plurality of sample points forming the γ correction curve, and specifically has a structure shown in FIG.

That is, it comprises a plurality of slide resistors 12 provided corresponding to the respective sampling points, and by sliding the slide terminals of these slide resistors 12 along the sliding groove 13, Each voltage value is generated according to the position of the slide terminal. Each of these voltage values becomes an input numerical value at each sample point of the γ correction curve.

The A / D converter 2 converts the inputted analog numerical values (voltage values) into digital data, and the interpolation circuit 3 performs an interpolation process between adjacent sample points of these digital data. , To approximately generate a γ correction curve. As the interpolation method of this interpolation processing, a method using a step function (Gaussian function), a linear interpolation method, a spline interpolation method, or the like is used, which will be described later.

A look-up table (LUT) 4 is created according to the γ correction curve thus generated. That is, it is a memory table for obtaining the converted data obtained by correcting each pixel data (data to be converted) of the image data stored in the frame memory 5 according to the γ correction curve. In the example described with reference to FIG. 4, image data 0-40
The range of 96 is set as an address, and the γ correction curve (the curve obtained by the interpolation circuit 3) is associated with each address.
It is a memory that stores the values converted into luminance data in the range of 0 to 255 according to.

The D / A converter 6 is a lookup table 4
Output (luminance data after conversion) is converted into an analog value and output to the display control unit 7. The display control unit 7 controls the display of the CRT 8 according to the input analog value.

The γ correction processing is executed through the following processing steps. The analog data (voltage values, data to be converted) of a plurality of sample points forming the γ correction curve input from each of the slide resistors 12 are converted into digital data by the A / D converter 2.

Since these input data are discontinuous values, these values are input to the interpolation circuit 3 and corrected to a continuous curve to be a γ correction curve. FIG. 2 shows the process of generating this γ correction curve.

Now, the slide resistor 12 of the input unit 1 gives sample point data an (n = 1 to k, here k = 10 for simplification). an is one of the data widths divided into k equal parts and means a singular point of the converted data (image data). For example, the converted data is 0
If the data has a width of ~ 1000, each slide resistor
The image data values have an interval of 100 (= an to an-1). This indicates the point of the X coordinate (horizontal axis in FIG. 2) of the XY coordinate system of the γ correction curve.

In the input unit 1, the slide resistor 12 converts the converted data (am, m = 1 to k) for each image data.
The brightness level) is input, and this value indicates the point of the Y coordinate (vertical axis in FIG. 2) of the XY coordinate system of the γ correction curve. Therefore, it is input to the interpolation circuit 3 by the A / D converter 2 as a point (an, am) on the XY coordinates of the γ correction curve.

The interpolation circuit 3 receives the input (an, am
) Is used to generate a γ correction curve.
As indicated by the curve a of, the curve formula that satisfies the equation Y = [X] (Gaussian function) is generated from the values of the two adjacent points.

As another example, as shown by the curve 10 in FIG. 2, the equation Y = aX can be calculated from the values of two adjacent points given.
A straight line formula for + b is created, and these points are connected to obtain a curved line formula.

As still another example, the equation of the curve 11 is generated by the spline interpolation function using the given three adjacent points.

The converted data (luminance data) for each value of the converted data (image data) "0 to 1000" is calculated using the equation of the curve generated by the interpolation circuit 3,
It is developed as the lookup table 4. For example, in the lookup table 4, addresses (0000) to
The converted data (image data) corresponds to each address of (1000), and the converted data calculated by the curve formula generated by the interpolation circuit 3 is stored at each address.

By doing so, each pixel data of the image data stored in the frame memory 5 is given to the lookup table 4 as an address, so that the converted luminance data can be obtained.

The slide terminals of the slide resistor 12 shown in FIG. 3 are slid up and down one by one along the groove 13 to input the numerical values of each sample while mechanically imagining the shape of the γ correction curve. You can Therefore, the operator can easily imagine the outline of the γ correction curve by virtually connecting the slide terminals.

[0027]

As described above, according to the present invention, a plurality of slide resistors are used to generate a voltage value corresponding to the position of a slide terminal, and a γ correction curve is created using each voltage value. As a result, there is an effect that it is possible to visualize the outline of the γ correction curve based on the positional relationship of each slide terminal.

Further, since the numerical value input section and the interpolation section for the γ correction curve are made into hardware, there is an effect that the delay of the processing caused by software can be eliminated and the processing can be speeded up.

[Brief description of drawings]

FIG. 1 is a system block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of interpolation of a γ correction curve.

FIG. 3 is a plan view showing a specific structure of an input unit.

FIG. 4 is a diagram showing an example of a relationship between image data and luminance data.

[Explanation of symbols]

 1 Input Section 3 Interpolation Circuit 4 Lookup Table 5 Frame Memory 8 CRT 12 Slide Resistor

Claims (4)

[Claims] 1. A gamma correction circuit of an image display device for converting input image data according to a preset gamma correction curve, and displaying the image by the converted data, which constitutes the gamma correction curve. A plurality of slide resistors provided corresponding to a plurality of sample points and having slidable slide terminals to generate voltage values corresponding to the positions of the slide terminals, and the respective slide resistors. A gamma correction circuit comprising: a curve generation means for approximately generating a gamma correction curve using a voltage value; and means for converting the input image data according to the gamma correction curve and displaying the image. 2. The gamma correction circuit according to claim 1, wherein the curve generating means creates the gamma correction curve by using a step function depending on adjacent sample points. 3. The gamma correction circuit according to claim 1, wherein the curve generating means creates the gamma correction curve by using a linear interpolation method between adjacent sample points. 4. The γ correction circuit according to claim 1, wherein the curve generating means creates the γ correction curve by using a spline interpolation method between adjacent sample points.