JPH1141503A - Device and method for photographing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform image processing, with which picture quality degradation such as noise or block distortion is not conspicuous, by performing compression not to execute quantization when character data are included in divided image data. SOLUTION: An inputted digital image signal is divided into blocks composed of the respective prescribed numbers of pixels arranged in vertical and horizontal directions by a raster block converting part 201. It is discriminated by a CPU 112 whether these matrix data include the character data generated by a character generator or not. When the character data are not included, a switch 202 is connected to a DCT part 203. The DCT executed matrix data are quantized by a quantizing part 205 and inputted to a Huffman coding part 206. When the character data are included, the switch 202 is connected to a DCT part 204. The DCT executed matrix data are inputted to the Huffman coding part 206 without being quantized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image capturing apparatus and an image capturing method for processing a captured image.

[0002]

2. Description of the Related Art As a conventional image compression method of an image photographing apparatus, there is a compression method called JPEG. Hereinafter, this compression method will be described.

[0003] First, a raster digital image composed of luminance and color difference is divided into 8 x 8 dot blocks, and each of the divided digital images is represented by an 8 x 8 square matrix (hereinafter referred to as "matrix data"). ").

Next, a transform called a discrete cosine transform (hereinafter referred to as "DCT") is performed on the matrix data. The transformed matrix data is called a DCT coefficient. The upper left term of the matrix is a value indicating the magnitude of the low frequency component of the original image, and the lower right term is a value indicating the magnitude of the high frequency component of the original image. .

Subsequently, each of the matrix data is divided by a coefficient table called a quantization table. The quantization table is weighted for high-frequency components, and the result of the division becomes matrix data indicating a smaller value for higher-frequency components.

Next, the matrix data is quantized, and values below a certain value are rounded down to zero. As a result, in the matrix data, the value of the lower right term is almost 0.

[0007] Next, this matrix data is converted into a data string arranged in a line in an order called zigzag scan, and a conversion called Huffman coding is performed. Since this conversion is a conversion in which a redundant portion of data (a data portion where the same value continues) is represented by another short code, data of a portion where 0s continue in the data sequence is significantly shortened. Can be compressed.

[0008] The extension method is as follows.

First, Huffman inverse encoding is performed on the compressed image data to obtain an original data string. Next, this data sequence is returned to matrix data, and multiplication is performed using the quantization table.
In the matrix data obtained at this time, 0 is larger in the high-frequency component as compared with the DCT coefficient.

Next, an inverse DCT transform is performed on the matrix data, and the blocks are arranged as before to obtain an expanded digital image.

Although this digital image has less high-frequency components than the digital image before compression due to the above-mentioned quantization, it is generally considered that the human eyes are insensitive to the high-frequency components, so that the deterioration of the image quality is not conspicuous. ing.

Although the JPEG compression described above is a compression method for a still image, it can be applied to a moving image by continuously processing the still image.

[0013]

However, the JPE
The information lost due to the quantization of G compression is not completely restored to the original state even after expansion, so that the noise called mosquito noise and the boundaries of blocks divided at the time of compression become noticeable near the outline of the expanded image. An obstacle such as block distortion may appear. These obstacles are particularly likely to occur in a portion having a high frequency component. Therefore, when an original image including an image having a large outline and a large number of high-frequency components generated by a character generator such as a date display is compressed / expanded, the influence thereof becomes conspicuous.

The present invention has been made in view of the above points, and has as its object to provide an image photographing apparatus and an image photographing method capable of performing image processing in which image quality deterioration such as noise and block distortion is not conspicuous. I do.

[0015]

In order to achieve the above object, an image photographing apparatus according to claim 1 comprises character data generating means for generating character data consisting of a predetermined number of pixels arranged in each of a vertical direction and a horizontal direction; Along with synthesizing the image data input by photographing and the character data generated by the character data generating means, the synthesized image data is divided into blocks each including a predetermined number of pixels arranged in the vertical direction and the horizontal direction, An image compressing unit that compresses the divided image data in units of blocks, when the character data is included in the divided image data, the image compression unit performs quantization. If the divided image data does not include the character data, the image compression means performs compression for performing quantization. The features.

According to a second aspect of the present invention, in the image capturing apparatus according to the first aspect, the compression is JPEG compression.

According to a third aspect of the present invention, there is provided the image capturing apparatus according to the first or second aspect, further comprising a marker issuing means for issuing a marker for determining the compressed image data which is not subjected to the quantization. It is characterized by having.

According to a fourth aspect of the present invention, an image photographing apparatus divides image data inputted by photographing into blocks each having a predetermined number of pixels arranged in a vertical direction and a horizontal direction, and divides the divided image data into blocks. An image compression unit for compressing the image data, and a setting unit for setting an area to be compressed by the image compression unit on the image data input by the photographing.

According to a fifth aspect of the present invention, in the image capturing apparatus according to the fourth aspect, the area set by the setting means is a compression area where quantization is not performed or a compression area where quantization is performed. It is characterized by.

According to a sixth aspect of the present invention, in the image capturing apparatus according to the fifth aspect, the setting means sets the compression area in which the quantization is not performed at a central portion of the image data input by the imaging. It is characterized by having such a configuration.

According to a seventh aspect of the present invention, in the image photographing apparatus according to the fifth or sixth aspect, the marker issuance means for issuing a marker for discriminating the compressed image data without performing the quantization. It is characterized by having.

According to a still further aspect of the present invention, there is provided a character image generating method for generating character data composed of a predetermined number of pixels arranged in a vertical direction and a horizontal direction; Is combined with the character data generated in step (a), and the combined image data is divided into blocks each having a predetermined number of pixels arranged in the vertical and horizontal directions, and the divided image data is compressed in units of the blocks. An image compression method including: performing compression without performing quantization in the image compression step when the character data is included in the divided image data. If the character data is not included in the data, compression is performed to perform quantization in the image compression step.

According to a ninth aspect of the present invention, in the image capturing method of the eighth aspect, the compression is JPEG compression.

According to a tenth aspect of the present invention, there is provided the image capturing method according to the eighth or ninth aspect, further comprising a marker issuing step of issuing a marker for determining the compressed image data that is not subjected to the quantization. It is characterized by the following.

In the image photographing method according to the present invention, the image data inputted by photographing is divided into blocks each having a predetermined number of pixels arranged in a vertical direction and a horizontal direction, and the divided image data is divided into blocks. An image compression step of compressing, and a setting step of setting an area to be compressed in the image compression step on the image data input by the photographing are included.

According to a twelfth aspect of the present invention, there is provided an image capturing method according to the eleventh aspect.
In the image capturing method described above, the region set in the setting step is a compression region where quantization is not performed or a compression region where quantization is performed.

According to a thirteenth aspect of the present invention, there is provided an image capturing method according to the twelfth aspect.
In the image capturing method described above, a compression area in which the quantization is not performed in the setting step is set in a central portion of the image data input by the capturing.

According to a fourteenth aspect of the present invention, there is provided the image capturing method according to the twelfth aspect.
14. The image capturing method according to claim 13, further comprising a marker issuing step of issuing a marker for determining the compressed image data that is not subjected to the quantization.

[0029]

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

(1) First Embodiment FIG. 1 shows a configuration of an image photographing apparatus according to a first embodiment of the present invention.

The image photographing apparatus according to the first embodiment of the present invention comprises a video camera. The video camera includes a lens 101 for capturing an image of a subject, an image sensor 102 for converting the captured image of the subject into an image signal, a CDS / AGC 103 for sampling and holding the image signal to obtain an appropriate signal level, and a CDS. A / D conversion of an image signal from AGC 103 and digital signal processing for digital signal processing, and character generator 1 as character data generating means for generating a character signal
05, an image compression circuit 106 as image compression means for JPEG-compressing the image signal from the digital signal processing circuit 104, an area for recording the image signal compressed by the image compression circuit 106, and a sub-record for recording other data. A recording medium 107 having a code area and an image expansion circuit 108 for expanding a compressed image signal from the recording medium 107 are provided.

Further, in this video camera, a signal changeover switch 109 for switching a signal to the digital signal processing circuit 104 side during a photographing state and a signal changeover side to an image expansion circuit 108 during tape reproduction, and a signal selected by the signal changeover switch 109. A / D conversion to NTSC video signal NT
SC encoder 111 and viewfinder 110
And a CPU 112 for detecting whether the character generator 105 is generating a character signal and controlling the image compression circuit 106.

The character signal generated by the character generator 105 is character data composed of a predetermined number of pixels arranged in the vertical direction and the horizontal direction, that is, 8 × 8 dots.

FIG. 2 shows a detailed configuration of the image compression circuit 106 of FIG. The image compression circuit 106 includes a raster-block transform unit 201, a switch 202, discrete cosine transform (hereinafter referred to as “DCT”) units 203 and 204, a quantizer 205, and a Huffman encoder 206 as a marker issuing unit. And a Huffman table 208 required for performing conversion called Huffman encoding in the Huffman encoding unit 206, and a quantization table 207 used for performing division in the quantization unit 205.

Next, the processing of the image compression circuit 106 will be described. First, a digital image signal composed of luminance / color difference in a raster format input to the raster-to-block converter 201 is a predetermined number of pixels arranged in the vertical and horizontal directions by the raster-to-block converter 201, that is, 8 × 8. The data is divided into blocks of dots, each of which is represented by an 8 × 8 square matrix (hereinafter referred to as “matrix data”).

A character generator 105 is added to the matrix data.
Whether or not the character data generated in
The switch 202 is connected to the DCT converter 204 when character data is included, and the switch 202 is connected to the DCT converter 203 when character data is not included.

Next, DCT transform sections 203 and 204 perform DCT transform on these matrix data. The matrix data after the conversion is called DCT coefficient and is also 8 × 8 matrix data. The upper left term of the matrix is a value indicating the magnitude of the low frequency component of the original image, and the lower right term is the original. This is a value indicating the magnitude of the high frequency component of the image.

Subsequently, the quantization unit 205 divides each of the matrix data as DCT coefficients by a coefficient table called a quantization table. The quantization table is weighted to low frequency components, and the result of the division becomes matrix data indicating a smaller value as the frequency component increases. Also, the quantization unit 205 quantizes the divided matrix data, and rounds down values below a certain value to zero. As a result, in the matrix data, the value of the lower right term is almost 0.

Next, the matrix data is converted into a data sequence arranged in a row in an order called zigzag scan, and the Huffman coding unit 206 performs a conversion called Huffman coding.
Since this conversion is a conversion in which a redundant portion of data (a data portion where the same value continues) is represented by another short code, in the above data sequence, a data sequence of a portion where 0 continues is significantly shortened. The amount will be compressed.

FIG. 3 shows the image compression processing of the image compression circuit 106 of FIG. First, the digital image signal input to the raster-block conversion unit 201 is divided into a predetermined number of pixels arranged in the vertical and horizontal directions, that is, into blocks of 8 × 8 dots (step S31). This block is 8x8
Is represented by the matrix data of

Next, in step S32, the CPU 112 determines whether or not this block contains character data generated by the character generator 105.
FIG. 5 shows this determination. 5 is an image displayed on the viewfinder 110 of FIG.
2 is an enlarged view in which a part of an image displayed on the viewfinder 110 is extracted and enlarged. This enlarged view 502
Displays an area 503 containing no character data and an area 504 containing character data.

If no character data is included in the step S32, the switch 202
The DCT transformation unit 203 performs DCT transformation on the matrix data by the DCT transformation unit 203 (step S33). Then, DCT
The transformed matrix data is quantized by the quantization unit 205 (step S34), Huffman encoded by the Huffman encoding unit 206 (step S35), and recorded on the recording medium 107 as compressed data (step S36). The process ends.

If character data is included in step S32, the switch 202
4 and the DCT transform unit 204 converts the matrix data into D
A CT conversion is performed (step S37). The matrix data subjected to the DCT transform is not quantized, and
In step S38, Huffman coding is performed. Further, in order to identify the image at the time of image expansion, a marker indicating that quantization has not been performed is issued (step S39), and the marker is recorded on the recording medium 107 (step S36), followed by terminating the present process. This marker is recorded collectively in the subcode area of the recording medium 107 when the compression of the image of one field before being divided into blocks is completed.

FIG. 4 shows image expansion processing of the image expansion circuit 108 of FIG. First, the image decompression circuit 108
In step S41, a marker recorded in the subcode area provided in the storage medium 107 is obtained.
Is read, and the read compressed data is Huffman-decoded (step S42).

Next, in step S43, the CPU 1
In step 12, it is determined whether the Huffman-decoded data is quantized data. If the data is quantized data, the data is inversely quantized (step S44) and inverse DCT transformed (step S45). On the other hand, if the data is not quantized, the inverse DCT is directly performed without performing the inverse quantization (step S45).

Thereafter, the data subjected to the inverse DCT transformation is combined (step S46), and the combined data is output as an image signal to the NTSC encoder 111 (step S47), and this processing ends.

As described above, according to the first embodiment, the digital image signal input to the raster-to-block converter 201 is divided into a predetermined number of pixels in the vertical and horizontal directions, that is, 8 × 8 pixels. It is divided into dot blocks (step S31), and it is determined whether or not this block contains character data generated by the character generator 105.
The determination is made in U112 (step S32). If character data is included, the quantization is not performed on the matrix data constituting the block, so that the compression of this block is reversible and can be completely restored. Image processing in which image quality deterioration such as block distortion is not conspicuous can be performed.

(2) Second Embodiment The configuration of an image capturing apparatus according to a second embodiment of the present invention is substantially the same as the configuration of the image capturing apparatus according to the first embodiment. The image photographing apparatus according to the second embodiment has a new setting means for setting an area where the digital image signal input to the raster-block converter 201 is not quantized.

FIG. 7 shows the image compression processing of the image compression circuit 106. First, as shown in FIG. 6, the user sets an area not to be quantized by aa 'and bb' to set the area by the setting means (step S71). This setting is
2 is notified. The user can set aa ',
Since the position of bb ′ can be changed freely, the ratio of the non-quantized area and the quantized area can be changed freely, and the amount of data recorded on the recording medium 107 described later can be adjusted. Further, by setting the positions of aa ′ and bb ′ at the center of the screen as shown in FIG. 6, noise and block distortion can be made inconspicuous.

Next, the digital image signal input to the raster-block converter 201 is divided into a predetermined number of pixels arranged in the vertical and horizontal directions, that is, into blocks of 8.times.8 dots (step S72). This block is represented by 8 × 8 matrix data.

Next, in step S73, the CPU 112 determines whether or not this block is included in the non-quantized area set by the setting means.

If it is determined in step S73 that the data is included in the non-quantized area, the switch 202
And performs DCT transform on the matrix data by the DCT transform unit 203 (step S74). Then, DCT
The transformed matrix data is quantized by the quantization unit 205 (Step S75), Huffman encoded by the Huffman encoding unit 206 (Step S76), and recorded on the recording medium 107 as compressed data (Step S77). This processing ends.

If the data is included in the area to be quantized in step S73, the switch 202 is connected to the DCT converter 204, and the DCT converter 204
A CT conversion is performed (step S78). The matrix data subjected to the DCT transform is not quantized, and
The Huffman coding is performed at step 06 (step S79). Further, in order to identify the image at the time of image expansion, a marker indicating that quantization has not been performed is issued (step S80), recorded on the recording medium 107 (step S77), and the present process is terminated. This marker is recorded collectively in the subcode area of the recording medium 107 when the compression of the image of one field before being divided into blocks is completed.

The image decompression processing of the data recorded on the recording medium 107 is the same as the processing described in the first embodiment with reference to FIG. 4, and a description thereof will be omitted.

As described above, according to the second embodiment, as shown in FIG.
Setting can be made by the setting means by dividing by aa 'and bb' (step S71), and the positions of aa 'and bb' are set at the center of the screen as shown in FIG. By doing
Since the compression of the area delimited by aa ′ and bb ′ is not quantized and is reversible and can be completely restored, it is possible to perform image processing in which image quality deterioration such as noise and block distortion is not conspicuous. it can.

[0056]

As described above in detail, according to the image photographing apparatus of the first aspect or the image photographing method of the eighth aspect, character data consisting of a predetermined number of pixels arranged in the vertical direction and the horizontal direction is generated. Then, the image data input by shooting and the generated character data are combined, and the combined image data is divided into blocks each including a predetermined number of pixels arranged in a vertical direction and a horizontal direction. If the data contains character data, compression without quantization is performed.If the divided image data does not include character data, compression is performed with quantization. Since the compression of the divided image data containing is reversible without quantization and can be completely restored,
Image processing in which image quality deterioration such as noise and block distortion is not conspicuous can be performed.

According to the image photographing apparatus of the present invention, the image data inputted by photographing is divided into blocks each having a predetermined number of pixels arranged in the vertical and horizontal directions, and divided. The compressed image data is compressed in units of blocks, and the area to be compressed is set on the image data input by shooting. Therefore, the area to be compressed can be set freely, and image quality degradation such as noise and block distortion is reduced. Inconspicuous image processing can be performed.

According to the image photographing apparatus of the sixth aspect or the image photographing method of the thirteenth aspect, a compression area where quantization is not performed is set at the center of image data input by photographing, so that noise and block are reduced. Distortion can be made inconspicuous.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image photographing apparatus according to a first embodiment of the present invention.

FIG. 2 is a detailed configuration diagram of an image compression circuit 106 of FIG.

FIG. 3 is a flowchart illustrating an image compression process of an image compression circuit shown in FIG. 1;

FIG. 4 is a flowchart showing image expansion processing of an image expansion circuit shown in FIG. 1;

FIG. 5 is a diagram showing a state of determining whether character data generated by a character generator 105 is included in a divided block.

FIG. 6 is a diagram showing a state where an area not quantized is set by a setting unit.

FIG. 7 is a flowchart showing an image compression process of the image compression circuit 106.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Lens 102 Image sensor 103 CDS / AGC 104 Digital signal processing circuit 105 Character generator 106 Image compression circuit 107 Recording medium 108 Image expansion circuit 109 Signal selection switch 110 Viewfinder 111 A / D converter / NTSC encoder

Claims (14)

[Claims] 1. A character data generating means for generating character data composed of a predetermined number of pixels arranged in each of a vertical direction and a horizontal direction, and image data input by photographing and character data generated by the character data generating means. While synthesizing,
An image photographing apparatus comprising: an image compression unit that divides the synthesized image data into blocks each including a predetermined number of pixels arranged in a vertical direction and a horizontal direction, and compresses the divided image data in units of the blocks. When the character data is included in the divided image data, compression is performed without performing quantization by the image compression unit, and when the character data is not included in the divided image data, Wherein the image compression means performs compression for performing quantization. 2. An apparatus according to claim 1, wherein said compression is JPEG compression. 3. The image photographing apparatus according to claim 1, further comprising a marker issuing unit that issues a marker for determining the compressed image data that is not subjected to quantization. 4. Image compression means for dividing image data input by shooting into blocks each having a predetermined number of pixels arranged in a vertical direction and a horizontal direction, and compressing the divided image data in units of the blocks. Setting means for setting an area to be compressed by the image compressing means on the image data input by the photographing. 5. The image photographing apparatus according to claim 4, wherein the area set by said setting means is a compression area where quantization is not performed or a compression area where quantization is performed. 6. The image according to claim 5, wherein the setting unit is configured to set the compression area in which the quantization is not performed at a central portion of the image data input by the photographing. Shooting equipment. 7. The image photographing apparatus according to claim 5, further comprising a marker issuing unit that issues a marker for determining the compressed image data that is not subjected to the quantization. 8. A character data generating step of generating character data composed of a predetermined number of pixels arranged in each of a vertical direction and a horizontal direction; and image data input by photographing and character data generated in the character data generating step. And dividing the combined image data into blocks each having a predetermined number of pixels arranged in a vertical direction and a horizontal direction, and compressing the divided image data in units of the blocks. In the image capturing method, when the character data is included in the divided image data, compression is performed without performing quantization in the image compression step, and the character data is included in the divided image data. If not, a compression method for performing quantization in the image compression step is performed. 9. The method according to claim 8, wherein the compression is JPEG compression. 10. The image photographing method according to claim 8, further comprising a marker issuing step of issuing a marker for determining the compressed image data that is not subjected to the quantization. 11. An image compression step of dividing image data input by shooting into blocks each having a predetermined number of pixels arranged in a vertical direction and a horizontal direction, and compressing the divided image data in units of the blocks. Setting a region to be compressed in the image compression step on the image data input by the photographing. 12. The method according to claim 11, wherein the area set in the setting step is a compression area where quantization is not performed or a compression area where quantization is performed. 13. The image photographing method according to claim 12, wherein in the setting step, the compression area in which the quantization is not performed is set at a central portion of the image data input by the photographing. 14. The image photographing method according to claim 12, further comprising a marker issuing step of issuing a marker for discriminating the compressed image data without performing the quantization.