JPH11134479A - Mosaic processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute a mosaic processing with less code quantity at the time of encoding the image of a mosaic-processed part by permitting the boundaries of blocks where image element values are replaced with prescribed values to really coincide with the boundaries of the blocks to be encoded. SOLUTION: A special effect performing part 100 receives an image signal from the external part of a mosaic processor such as an imaging device, etc., divides an image based on the image signal into plural blocks and replaces the image element values of the whole blocks with their average values as against a mosaic-processed area. In this case, boundaries of the blocks are made to coincide with the mosaic area 121. After that, a high efficiency encoding part 101 receives the image signal of an image 120 which is mosaic-processed by the special effect performing part 100 and encodes the mosaic image 120 at every block unit through the use of a DCT operation. Thus, much more encoding quantity is assigned to the area which is not mosaic-processed so that the image quality of the area is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mosaic processing device for performing mosaic processing on an image.

[0002]

2. Description of the Related Art Conventionally, when an image is artificially processed and digital recording or digital transmission is performed, a process called a special effect is performed for the image processing. Among them, a process called a mosaic process is well known. The mosaic process is a process of replacing all pixel values in a block composed of a plurality of pixels with specific values. This is a process that is currently widely used as a technique for greatly reducing the amount of information in a specific area in a screen.

A conventional mosaic processing device for performing such a mosaic processing will be described with reference to FIGS.

FIG. 6 is a block diagram of a conventional mosaic processing apparatus. In FIG. 6, reference numeral 200 denotes a special effect unit;
1 is a high-efficiency encoding unit.

Next, the operation of such a conventional mosaic processing device will be described.

First, the special effect unit 200 inputs an image signal from the outside of a mosaic processing device such as an image sensor, and performs mosaic processing on an image based on the image signal in a predetermined area as described below. Do.

The mosaic processing will be described with reference to FIGS. FIG. 7 is an example of an image based on an image signal input by the special effect unit 200. 210 is the entire image. FIG. 8 is a diagram in which the image shown in FIG. 7 is divided into a plurality of blocks. Each of the smallest squares such as 220 and 221 shown in FIG. 8 is a block to be encoded by the high-efficiency encoding unit 201 later. In addition,
The block is composed of 8 × 8 pixels. FIG. 9 is a diagram illustrating an area where the mosaic processing is performed on the image illustrated in FIG. 7 or 8. 9, 230 is a block corresponding to the block 220 in FIG. 8, and 231 is a region to be mosaic-processed by the special effect unit 200.

The special effect unit 200 performs a mosaic process on the mosaic area 231. The mosaic processing means that, for each block of the mosaic area 231 divided by a dotted line, all pixel values in the dotted line block are replaced with an average value of all pixel values in the dotted line block. The size of the dotted block is 8 × 8 pixels. That is, the size of each of the blocks separated by the dotted line matches the size of each of the blocks separated by the solid line.

Here, FIG. 10 shows a diagram subjected to the mosaic processing. In FIG. 10, reference numeral 240 denotes the entire mosaic image after the mosaic processing. 241 is mosaic image 2
This is the area of 40 that has been actually mosaiced. The entire mosaic image 240 corresponds to the entire screen 210 in FIG. 7, and the mosaic area 241 corresponds to the area 231 to be mosaiced in FIG. In FIG. 10, the same pattern portion in the mosaic area 241 corresponds to the special effect unit 200.
Indicates that each pixel value has been converted to the same value. In other words, the pixels of the same pattern in the mosaic area 241 have the same value.

After that, the high-efficiency encoding unit 201 inputs an image signal of the image 240 that has been mosaic-processed by the special effect unit 200, encodes the image 240 in block units separated by solid lines, The encoded data is output outside the mosaic processing device.

[0011]

As described above, in the conventional mosaic processing device, in the area 241 mosaiced by the special effect unit 200, a portion having different pixel values occurs in one solid line block. There is. In other words, the boundary between the solid line block and the boundary between the dotted line blocks of the mosaic area 241 may not coincide.

For convenience of explanation, the following description focuses on the noted block 211 of FIG. 8 which is one of the solid-line blocks and the corresponding noted block 242 of FIG. FIG.
8 shows a signal waveform diagram of the image before the mosaic processing, that is, the target block 221 of the original image in FIG. FIG. 12 shows a signal waveform diagram of the image after the mosaic processing, that is, the block of interest 242 of the mosaic image 240 in FIG. x
The axis, the y-axis, and the z-axis indicate the horizontal pixel position, the vertical pixel position, and the pixel value in the block of interest 221 or 242, respectively. Attention block 221 in FIG.
It can be seen that the signal waveform of FIG. On the other hand, a very steep edge appears in the signal waveform of the region of interest 242 in FIG. In other words, there is a step. This is newly created by the mosaic processing, and the block of interest 242
This is because four types of pixel areas having different numerical values have occurred. The edge is an edge that did not exist in FIG.

Next, FIG. 13 shows that the original image shown in FIG.
The DCT coefficient of the block of interest 221 when the T operation is performed is shown. FIG. 14 shows the DCT coefficients of the block of interest 242 when the DCT operation is performed on the mosaic image 240 of FIG. The x-axis indicates the horizontal frequency in the block of interest 221 or 242, and x
Indicates that the higher the value, the higher the frequency component.
The y-axis indicates the vertical frequency in the block of interest 221 or 242, and indicates that the larger the value of y, the higher the frequency component. The z-axis indicates the magnitude of the DCT coefficient of each frequency component in the block of interest 221 or 242. 250 or 26
0 is a frequency component of x = 0 and y = 0, and is called a DC component. Other frequency components are called AC components. In general, an image can be divided into a plurality of images with different degrees of precision, of which the DC component is the image with the lowest precision, and the AC component is the image with higher precision as the frequency increases. Dividing the image into a plurality of images having different degrees of precision is called orthogonal transformation. 14-2
Reference numeral 61 denotes a frequency component representing an edge generated by the mosaic processing, and is a very high frequency component that did not exist in the target block 221 in the original image shown in FIG.

[0014] As shown in FIG.
Is divided into a DC component and several lower frequency AC components. On the other hand, as shown in FIG. 14, the block of interest 242 is divided into an AC component having several high frequencies in addition to a DC component and several low-frequency AC components.

When the high-efficiency coding unit 201 codes the block of interest 221 or 242, the high-efficiency coding unit 201 assigns a code amount to the DCT coefficient after the DCT operation, and , And performs variable-length encoding to generate encoded data. Although the number of codes assigned to the block of interest 221 shown in FIG. 13 is very small, the block of interest 242 shown in FIG. 14 has a very high frequency domain DCT coefficient of the AC component. It is necessary to allocate a large amount of code. For this reason, the amount of code allocated to an area that has not been subjected to the mosaic processing other than the mosaic area 241 such as the block of interest 242 is reduced, and the image quality of that part is significantly deteriorated.
Conversely, if the code amount assigned to the block of interest 242 is reduced, the image quality of the block of interest 242 will be significantly degraded, and the visual effect of performing the mosaic processing will not be effective.

According to the present invention, in a conventional mosaic processing apparatus,
In consideration of the problem that the code amount may increase when encoding the image of the mosaiced portion, mosaic processing is performed to reduce the code amount when encoding the image of the mosaiced portion. It is an object to provide a mosaic processing device.

[0017]

According to a first aspect of the present invention, an image signal is input, and a value of a pixel in each block obtained by dividing a predetermined region of an image based on the image signal is determined. Pixel value replacement means for replacing the pixel value with the pixel value replacement means, and coding means for inputting an image signal from the pixel value replacement means and coding an image of the image signal in predetermined block units. The mosaic processing apparatus is characterized in that a boundary of a block in which the pixel value is replaced by a predetermined value by the means substantially coincides with a boundary of a block to be encoded by the encoding means.

[0018]

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

(Embodiment 1) The configuration of a mosaic processing apparatus according to Embodiment 1 of the present invention, together with its operation, will be described with reference to the drawings.

FIG. 1 shows a block diagram of a mosaic processing apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 100 denotes a special effect unit, and 101 denotes a high-efficiency encoding unit.

First, the special effect unit 100 inputs an image signal from outside the mosaic processing device such as an image sensor, and divides an image based on the image signal into a plurality of blocks. As will be described later, the high-efficiency encoding unit 101 is
Encode the image from. At this time, the encoding is performed for each block. So, in the special effects section 100,
The high-efficiency encoding unit 101 presets information of a block when encoding an image, and based on the information, the special effect unit 100 divides an image based on an input image signal into a plurality of blocks. Each block is composed of 8 × 8 pixels. And, the special effects section 10
0 performs mosaic processing on a predetermined area as shown below.

The mosaic processing will be described with reference to FIGS. FIG. 2 is an example of an image based on an image signal input by the special effect unit 100. Reference numeral 110 denotes one block of the image, and 111 denotes an area where the mosaic processing is performed. In FIG. 2, the entire image is divided into a plurality of blocks and displayed.
It is divided by 0.

The special effect unit 100 performs a mosaic process on the area 111. The mosaic processing means that all pixel values of a block to be subjected to the mosaic processing are replaced with an average value of all pixel values in the block for each block. FIG. 3 shows the result of the mosaic processing. In FIG. 3, reference numeral 120 denotes the entire mosaic image after the mosaic processing, 121 denotes an area of the mosaic image 120 where the mosaic processing is actually performed, and 122 denotes a block of interest in the mosaic processing area 121. The focused block 122 is the same as the focused block 242 of FIG. 10 described in the conventional example. As can be seen from FIG. 3, the boundaries between the blocks and the mosaic area 1
21 coincides with the boundary.

In the following, the mosaic processing and encoding of the block of interest 122 as a representative block of the mosaic area 121 will be described.

Here, the signal waveform of the block of interest 122 is shown in FIG. The x-axis, the y-axis, and the z-axis indicate the horizontal pixel position, the vertical pixel position, and the pixel value in the block of interest 122, respectively. As is clear from FIG. 4, the signal waveform of the block of interest 122 is completely flat. This is because the values of all the pixels in the block have been replaced by the average value of all the pixels in the block by the mosaic processing.

After that, the high-efficiency encoding unit 101 inputs the image signal of the image 120 that has been mosaic-processed by the special effect unit 100, and encodes the mosaic image 120 for each block by using the DCT operation. .

FIG. 5 is a diagram showing DCT coefficients of the block of interest 122 when the high-efficiency encoding unit 101 performs a DCT operation on the mosaic image 120. The x-axis indicates the horizontal frequency in the block of interest 122, and the larger x indicates the higher frequency component. The y-axis indicates the vertical frequency in the target block 122, and indicates that the larger the value of y, the higher the frequency component. The z-axis indicates the magnitude of the DCT coefficient of each frequency component in the block of interest 122. 130
Is a frequency component of x = 0 and y = 0, and is called a DC component. Other frequency components are called AC components. As is clear from FIG. 5, the target block 122 has only a DC component. Therefore, the amount of code allocated to the block of interest 122 by the high-efficiency coding unit 101 is much larger than the amount of code allocated to the block of interest 242 in the conventional example shown in FIG. Less. Also, the encoded data becomes complete.

Thus, a larger amount of code can be assigned to an area other than the block of interest 122 and the like that has not been subjected to the mosaic processing, so that the image quality of that area can be improved.

Finally, the high-efficiency encoding section 101 outputs the encoded data to the outside of the mosaic processing device.

In the present invention, the special effect unit 100 is used as the pixel value replacing means, and the high efficiency coding unit 1 is used as the coding means.
01 was used.

Also, in the above-described embodiment, the block to be mosaiced and the block to be coded are the same.
The block to be encoded does not necessarily have to match. The block to be coded may be smaller than the mosaiced block. In short, the block to be encoded only needs to be an area where pixels having a certain value are gathered by the mosaic processing.

Further, in the first embodiment, the high-efficiency encoding section 101 performs encoding using DCT operation. However, the high-efficiency encoding section 101 divides an image into frequencies using orthogonal transform. And if it encodes it, DC
The image may be encoded by encoding other than the encoding using the T operation.

[0033]

As is apparent from the above description, the present invention provides a mosaic processing apparatus for performing mosaic processing so as to reduce the code amount when coding an image of a mosaiced portion. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram of a mosaic processing device according to a first embodiment of the present invention.

FIG. 2 is an example of an image based on an image signal input by a special effect unit of the mosaic processing device according to the first embodiment of the present invention;

FIG. 3 is a diagram in which a mosaic processing is performed on a mosaic area of the image in FIG. 2;

FIG. 4 is a region of interest 122 of an image after mosaic processing.
Signal waveform diagram

FIG. 5 is a diagram illustrating a mosaic process performed by a special effect unit of a conventional special effect device.

FIG. 6 is a block diagram of a conventional mosaic processing device.

FIG. 7 illustrates an example of an image based on an image signal input by a special effect unit of a conventional mosaic processing device.

8 is a diagram in which the image of FIG. 7 is divided into a plurality of blocks.

FIG. 9 is a diagram showing an area where mosaic processing is performed on the image of FIG. 7 or 8;

FIG. 10 is a diagram in which a mosaic processing is performed on a mosaic area of the image in FIG. 9;

FIG. 11 shows a block 22 of the image before being subjected to the mosaic processing.
1 signal waveform diagram

FIG. 12 is a region of interest 24 of the image after the mosaic processing.
Signal waveform diagram of 2

FIG. 13 shows a DCT for an image before being subjected to mosaic processing.
The figure which showed the DCT coefficient of the block 221 at the time of performing operation.

FIG. 14 shows a DCT of the image after the mosaic processing.
The figure which showed the DCT coefficient of the attention area 242 at the time of performing operation.

[Explanation of symbols]

100, 200 Special effects unit 101, 201 High-efficiency coding unit 210 Whole image 110, 220, 230 Block 111, 231 Mosaic region of one image based on image signal input by special effects unit of conventional mosaic processing device 120, 240 Whole mosaic image after mosaic processing 121, 241 mosaic area 122, 221, 242 Attention block 130, 250, 260 DC component 261 Frequency component representing edge generated by mosaic processing

Claims (4)

[Claims] 1. A pixel value replacement means for receiving an image signal and replacing a pixel value in each block obtained by dividing a predetermined area of the image based on the image signal with a predetermined value, and Encoding means for inputting an image signal from the value substitution means and encoding the image of the image signal in predetermined block units, wherein the pixel value substitution means replaces a pixel value with a predetermined value. A mosaic processing apparatus, wherein a boundary of a block substantially coincides with a boundary of a block to be encoded by the encoding unit. 2. The mosaic processing apparatus according to claim 1, wherein said encoding means is an orthogonal transformation means. 3. The mosaic processing apparatus according to claim 2, wherein said orthogonal transform means is a DCT transform means. 4. The apparatus according to claim 1, wherein the size of the block for which the pixel value replacing means replaces the value of the pixel with a predetermined value is equal to the size of the block for coding by the coding means. The mosaic processing device according to any one of the above.