KR100256893B1 - Gamma compensation device for image data - Google Patents

Abstract

PURPOSE: A screen data gamma correction device is provided to acquire clean and clear screen image to satisfy characteristic of human sight sense by making a gamma correction adaptively considering qradation change of vertical and horizontal scanning direction. CONSTITUTION: A gamma correction is executed in a horizontal scanning direction comparing with present data, delaying screen image data in a horizontal direction in gamma correction device of screen image process system. Vertical qradation comparison device(70 to 100) compares with qradation change to be generated in vertical scanning direction of horizontal correction screen image data corrected in a horizontal scanning direction. The second gamma curve selection part(110) generate gamma curve selection signal combining signal output from vertical qradation comparison device. The second gamma conversion part(120) executes vertical direction gamma correction of above horizontal correction screen image data according to signal of above the second gamma curve selection part(110). Vertical qradation comparison device(70 to 100) is composed of the first line buffer(70) and the second line buffer(80) which stores temporary in turns top rank bit of horizontal correction screen image data, the first and the second gate(90,100) which control separately data output of above the first and the second line buffer(70,80) by a designated signal and the reverse signal.

Description

Image data gamma correction device

1 is a diagram showing the configuration of a conventional gamma correction circuit.

2 is a diagram showing the configuration of a gamma correction circuit according to the present invention.

3 is a diagram showing the configuration of a gamma selector.

4 is a diagram showing an example of a gamma curve employed in the present invention.

The present invention relates to an image input apparatus of an image processing system such as a digital copying machine, an image scanner, and more particularly, by correcting a difference between a response characteristic of a photosensitive device and a human viewing characteristic in a process of generating image data according to image reading. It relates to a gamma correction circuit (γ-correction device) capable of obtaining a high quality image.

A gamma correction device that is commonly used to perform gamma correction according to a predetermined gamma curve (γ-curve).

This fixed gamma curve simply compensates for the difference between the human viewing characteristics and the photosensitive device's response (or display characteristics of the device). There was a problem in that gamma correction of data could not be done efficiently.

A gamma correction method for compensating for such a deficiency has been disclosed in JP 62-328830, the configuration of which is briefly shown in FIG.

Briefly describing this conventional technique with reference to the first step, the digital video signal which is the output of the A / D converter 20 for converting the analog video signal generated by the CCD sensor unit 10 into a digital signal. D (n) (where n denotes the horizontal scanning order) is delayed by one clock in the horizontal direction for vertical synchronization by the flip-flop 30 so that the current digital video signal Dn, By comparing the digital video signals Dn and Dn-1 immediately before Dn-1, the? Gamma curve is selected by the first gamma conversion unit 50.

However, this method has a drawback that efficient gamma correction is not achieved by not considering manufacturing changes in the vertical scanning direction at all.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gamma correction apparatus for adaptively performing gamma correction of image data according to gray level changes in the vertical and horizontal scanning directions.

As a technical means for achieving the above object, the present invention provides a gamma correction apparatus of an image processing system for performing a gamma correction in the horizontal scanning direction compared to the current data by delaying the image data in the horizontal direction,

A second gray level comparison means for comparing gradation changes generated in the vertical scan direction of the horizontally corrected image data corrected in the horizontal scan direction with a signal output from the vertical tone comparison means to generate a? Curve selection signal; And a second gamma converter for performing vertical gamma correction of the horizontally corrected image data according to the signal of the second gamma curve selector.

According to another aspect of the present invention, the vertical tone comparison means includes two line buffers for temporarily storing the upper two bits of the horizontally corrected image data alternately by a predetermined control signal, and the predetermined control signal and its inverted signal. Thus, two gates each control data output of the two line buffers.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing a preferred embodiment of the present invention, wherein the configuration requirements indicated by reference numerals 10 to 50 are the configuration requirements to perform the same or similar functions as the configuration requirements of the prior art (see FIG. 1). The amplification part is shown.

In Fig. 2, reference numerals 70 to 120 denote new parts of the present invention, and the gradation comparison means 70 to 100 for comparing the gradation change in the vertical scanning direction with the conventional configuration, and the second? Curve selection unit 110. The second γ conversion table 120 has a configuration added thereto.

Line buffer memory for temporarily storing image data in line units indicated by reference numerals 70 and 80 in FIG. 2, 90 and 100 are gates for transferring data output from line buffer memories 70 and 80, and 110 and 120. Denotes a second γ curve selector and a second γ conversion table for vertical γ correction, respectively.

The first γ curve selector 40 and the second γ curve selector 110 may have the same configuration.

3 shows an example of a γ curve selector 40 or 110.

Now, the operation of the present invention having the above configuration will be described in detail.

In FIG. 2, the analog image signal obtained by the CCD sensor unit 10 is amplified to a predetermined level by the amplifier 60 and then provided to the A / D converter 20. FIG.

The A / D conversion unit 20 converts the analog image signal into a digital image signal having a predetermined number of bits.

At this time, the two-bit data Dn and Dn-1 of the most significant bit and the next higher bit among the digital image data Do through Dn of the predetermined bit output from the A / D converter 20 are provided to the flip-flop 30 to provide A / D. The data is temporarily stored until the next image data is output from the D conversion unit 20.

That is, the upper two bits Dn and Dn-1 of the image data are delayed for one clock.

If the 2-bit data delayed one clock by the flip-flop 30 is D'n, D'n-1, the delayed data D'n, D'n-1 is transmitted to the current A / D converter 20. Are supplied to the first? Curve selection unit 40 together with the upper two bits Dn and Dn-1 of the image data outputted from the?

The? curve selection unit 40 uses the same logic as that in Fig. 3 to show the upper two bits (Dn, Dn-1) of the current image data and the upper two bits (D'n, D'n-1) of the previous image data. ) Is compared to generate? Curve selection signals S0 and S1.

The gamma curve selection signals S0 and S1 are provided to the first gamma conversion 50 made of ROM, and gamma correction data VDo to VDn of the data Do to Dn to be input are output.

As described above, the flip-flop 30, the first? Curve selector 40, and the first? Transform unit 50 synchronize the current data with the previous data vertically, and thus the? Calibration is made.

The upper two bit data VDn and VDn-1 of the data VDo to VDn corrected in the horizontal scanning direction to perform γ correction according to the gray level change generated in the vertical scanning direction are the first and second line buffers 70 and 80. Are each provided.

Read / write signals provided from control means (not shown) such as a CPU to write and read data VDn and VDn-1 to these line buffers 70 and 80. Controlled by

When the first line buffer 70 is in a write enable state, the second line buffer 80 is in a read enable state.

The first gate 90 and the second gate 100 connected to the first line buffer 70 and the second line buffer 80 are also the read / write signals. These two gates 90 and 100 are in turn enabled and disabled, and transmit data provided from the line buffer 70 or 80 to the second? Curve selection unit 110.

More specifically, when the first line buffer 70 is in the lead-enabled state, the first gate 90 is also enabled, and when the second line buffer 80 is in the lead-enabled state, the first gate 90 is disabled. And the second gate 100 is enabled, and data output from the first line buffer 70 or the second line buffer 80 is transferred to the second? Curve selection unit 110.

The second γ curve selecting unit 110 generates the selection signals S'O and S'1 by comparing the current horizontal correction data VDn and VDn-1 with the previous horizontal correction data VD'n and VD'n-1. Let's do it.

The selection signals S'0 and S'1 are provided to the second γ conversion table 120 made of ROM to perform γ correction in the vertical scanning direction of the horizontal correction data VDo to VDn input to the table 120. do.

The second γ conversion unit 120 γ compensates the input data VDo through VDn according to a predetermined γ curve selected by the selection signals S'0 and S'1 provided from the second γ curve selection unit 110. The γ-corrected data VHDo to VHDn in the horizontal and vertical scanning directions are finally output.

As described above, the present invention can obtain a clear and clear image that satisfactorily satisfies the human viewing characteristics by adaptively performing gamma correction in consideration of grayscales in the vertical and horizontal scanning directions.

Claims (2)

A gamma correction apparatus of an image processing system which delays image data in the horizontal direction and performs gamma correction in the horizontal scanning direction compared with current data, wherein the gamma correction apparatus is generated in the vertical scanning direction of the horizontally corrected image data corrected in the horizontal scanning direction. The horizontal gamma curve selecting unit and the second gamma curve selecting unit generating a gamma curve selection signal by combining a vertical gray level comparison means for comparing the gray level change and a signal output from the vertical gray level comparison means. An image data gamma correction apparatus comprising a second gamma converter configured to perform vertical gamma correction of corrected image data. The first and second line buffers of claim 1, wherein the vertical gray level comparison means alternately temporarily stores the upper two bits of the horizontal correction image data by a predetermined control signal; An image comprising the first and second gates 90 and 100 for respectively controlling the data output of the first and second line buffers 70 and 80 according to the predetermined control signal and its inverted signal. Data Gamma Corrector.