JPH0638641B2 - Image processing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image processing method, and more particularly to a method of processing an image using a memory.

BACKGROUND ART Image processing such as image reduction, enlargement, and movement can be performed by digitizing a composite video signal and writing it in a memory, and by reading the digitized composite video signal from this memory by specifying an address different from that at the time of writing. It Also,
It is possible to obtain the afterimage effect by writing only a part of the composite video signal in the memory and synthesizing and outputting the part and the other part that has already been written.

However, for example, the frequency F _SC color subcarrier of the video signal of the NTSC system, the horizontal synchronizing frequency as F _H, the vertical synchronizing frequency is f _V in the frequency as shown in the following equation.

For this reason, the continuity of the color subcarriers of the output video signal to be combined and output in the composite video signal written in an arbitrary period is lost, and a normal color image cannot be obtained.

Therefore, an image processing apparatus as shown in FIG. 7 has been devised so that a normal color image can be obtained. In the figure,
The composite video signal is supplied to the Y-C separation circuit 1 and separated into a luminance signal Y and a color signal C. The luminance signal Y is A / D
After being converted into a digital signal by the converter 2, it is supplied to the memory 3. The color signal C is supplied to the color demodulator 4 and the color difference signals RY and BY are demodulated. These color difference signals RY and BY are converted into digital signals by A / D converters 5 and 6, respectively, and then supplied to the memory 3.

The memory 3 is subjected to address control or the like by the memory controller 7, and the digitized luminance signal Y and the color difference signals RY and BY are written therein. When the luminance signal Y and the color difference signals RY and BY are read from the memory 3, they are supplied to the D / A converters 8, 9 and 10 and converted into analog signals. The color difference signals R-Y and B-Y converted into analog signals are supplied to the modulator 11 and the color subcarriers are modulated to form the color signal C.
The color signal C is supplied to the addition circuit 12 and added to the luminance signal Y output from the D / A converter 8 to synthesize a composite video signal.

The circuit as described above has a drawback that the structure is complicated and the image quality is deteriorated by the color signal passing through the demodulator and the modulator.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image processing method capable of obtaining an afterimage effect without degrading image quality by a circuit having a simple structure.

According to the image processing method of the present invention, a screen on which an image is formed by a composite video signal is divided into a plurality of areas, and the image data at each point of the plurality of areas is written to each storage position of the corresponding memory. It is characterized in that it is performed only in a period selected for each of a plurality of regions from a plurality of periods existing in a 4-field cycle.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6.

In FIG. 1, a composite video signal is supplied to an A / D (analog / digital) converter 21, a field cycle processing circuit 22 and a level comparison circuit 23 via an input terminal IN. In the A / D converter 21, the composite video signal is sampled at a predetermined sampling frequency, and image data corresponding to the obtained sample value is generated. This A
The image data output from the / D converter 21 is stored in the memory 2
5 is supplied. The memory 25 has, for example, a storage capacity capable of storing all the image data generated in one field period, and also has a plurality of storage positions corresponding to respective points on the screen where an image is formed by the composite video signal. is doing.

The field cycle processing circuit 22 is configured to generate a positive pulse as shown in FIG. 2 which has a pulse width corresponding to one field period and which is generated in four field cycles by the vertical synchronizing signal in the composite video signal. ing. The output pulse of the field cycle processing circuit 22 is supplied to one input terminal of a 2-input AND (logical product) gate 24. The output of the level comparison circuit 23 is supplied to the other input terminal of the AND gate 24. The level comparison circuit 23 is configured to compare the composite video signal with the reference level Vr and output a high level signal when the instantaneous level of the composite video signal becomes equal to or higher than the reference level Vr.

The output of the AND gate 24 is supplied to the memory controller 26. The memory controller 26 controls the memory 25 so that the image data sequentially supplied to the memory 25 is sequentially written to the corresponding storage positions, and the storage data of each storage position of the memory 25 is sequentially read in a predetermined order. . In this memory controller 26, the AN
The high level signal output from the D gate 24 acts as a write command signal, and only when the high level signal is output from the AND gate 24, the image data to each storage position of the memory 25 is transferred. Writing is performed.

The image data read from the memory 25 is supplied to the D / A converter 27 and converted into an analog signal, and then supplied to the output terminal OUT and sent to a video reproducing device such as a color monitor.

In the above configuration, the third field
The operation of each unit when the composite video signal corresponding to the image as shown in FIG. Now, the reference level Vr applied to the level comparison circuit 23 is less than or equal to the instantaneous level of the portion corresponding to the bright areas A and B of the composite video signal and is higher than the instantaneous level of the portion other than the areas A and B. It is assumed that it is set to be large. Then, when the portions corresponding to the bright areas A and B of the composite video signal are supplied to the level comparison circuit 23, a high level signal is output from the level comparison circuit 23, and the AND gate 24 outputs one field period in four field cycles. A high level signal is output over the entire range. Area A
And a portion corresponding to a region other than B is the level comparison circuit 23.
, The output of the level comparison circuit 23 becomes low level, and the output of the AND gate 24 also becomes low level.

Since image data is written to each storage position of the memory 25 only when a high level signal is output from the AND gate 24, each storage of the image data of each point of the bright areas A and B in the corresponding memory 25 is stored. Continuous writing to position 4
It is performed only in one field period of the field period. Further, since the area A is moved, new image data is not written to the storage position where the image data of each point of the area A was written before the movement of the area A. As a result, an image having an afterimage is obtained as shown in FIG. At the same time, since the image data of the portion that forms the afterimage is written in a 4-field cycle, the phase continuity of the color subcarriers of the portion that forms the afterimage and the portion other than that is maintained, Good color reproduction is possible.

It should be noted that although images for three fields of the four-field period are thinned out, reproduced images for 15 fields are output per second, so that a normal image can be perceived as a moving image.

FIG. 4 is a block diagram showing another embodiment of the present invention, in which an A / D converter 21, a field cycle processing circuit 22,
Level comparison circuit 23, AND gate 24, memory 25,
The memory controller 26 and the D / A converter 27 have a first
It is connected in the same way as the illustrated device. However, in this example, the reference level supplied to the level comparison circuit 23 is output from the integration circuit 28. The input composite video signal is supplied to the integrating circuit 28.

In the above configuration, since the reference level supplied to the level comparison circuit 23 changes according to the average brightness level of the input composite video signal, an appropriate afterimage is obtained even when the brightness level is generally high or conversely low. There is an advantage that an effect can be obtained.

In the above embodiment, the image data at each point in the area where the instantaneous level of the composite video signal is high is written.
The image data of each point in the region where the instantaneous level of the composite video signal is low may be written. Further, in the above embodiment, the screen is divided according to the instantaneous level of the composite video signal, but the screen is divided into nine as shown in FIG. 5, and in the area A, as shown in FIG. It is also conceivable that the writing is carried out in the area B, and in the area B, the writing is carried out at a period of 16 fields as shown in FIG. 6 (B). Further, the writing cycle in the areas A and B may be changed at appropriate intervals.

As described in detail above, the image processing method according to the present invention divides a screen on which an image is formed by a composite video signal into a plurality of areas, and stores the corresponding memory data of image data at each point of the plurality of areas. Since the writing to each storage position is performed only in a period selected for each of a plurality of regions from a plurality of periods existing in a 4-field cycle, the continuity of the color subcarrier is maintained and the modulation for modulating / demodulating a color signal is performed. The color reproduction can be performed well without providing a converter and a demodulator, and the afterimage effect can be obtained by the circuit having a simple structure without degrading the image quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a field cycle processing circuit 22 in the apparatus of FIG.
FIG. 3 is a waveform diagram showing the output of FIG. 3, FIG. 3 is a diagram showing the operation of the device of FIG. 1, FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG. 5 is a screen division method. 6 and 6 show the writing timing of each storage position of the memory corresponding to each point of each area when divided as shown in FIG. 5, and FIG. 7 shows a conventional image processing method. It is a block diagram shown. Explanation of symbols of main parts 22 ... Field cycle processing circuit 23 ... Level comparison circuit 25 ... Memory 26 ... Memory controller

Claims (2)

[Claims] 1. A composite of each point on the screen obtained by sampling the composite video signal in a memory having a plurality of storage locations corresponding to each point on the screen where an image is formed by the composite video signal. Image processing is performed by sequentially supplying a plurality of image data corresponding to the level of the video signal and writing the corresponding data in the corresponding plurality of storage positions, and then sequentially reading the storage data of the plurality of storage positions in a predetermined order. An image processing method to be performed, wherein the screen is divided into a plurality of areas, and the image data of each point of the plurality of areas is written to each corresponding storage position of the memory at a period of four field periods. The image processing method is performed only during a period selected for each of the plurality of regions from among the plurality of periods. 2. The method according to claim 1, wherein the instantaneous level of the composite video signal is compared with a predetermined reference level, and the screen is divided into a plurality of areas according to the obtained comparison result. Image processing method.