KR100634568B1 - Method for processing image signal capable of controlling jpeg file size and apparatus thereof - Google Patents

Abstract

An image processing method and an apparatus thereof are provided to control a JPEG file size by controlling a filter included in the image processing apparatus to prevent buffering memory overflow. An image processing apparatus(320) includes an image signal processor(330), a JPEG encoder(340), and a file size controller(350). The image signal processor includes a smoothing filter for converting a high-frequency component of a video signal into a low-frequency component. The JPEG encoder compresses video data inputted from the video processor. The file size controller measures the quantity of video data outputted from the JPEG encoder and controls on/off of the smoothing filter of the image signal processor in response to the measured quantity of video data. The file size controller operates the smoothing filter when the quantity of video data is greater than a predetermined reference value and does not operate the smoothing filter when the quantity of video data is smaller than the reference value.

Description

Method for processing image signal capable of controlling JPEG file size and Apparatus

1 is a block diagram illustrating a typical JPEG encoder.

2 is a block diagram illustrating a typical JPEG decoder.

3 is a block diagram illustrating an image processing apparatus according to an exemplary embodiment of the present invention.

4 is a block diagram illustrating an image processor for processing image data according to an exemplary embodiment of the present invention.

5 is a Gaussian filtering flowchart performed in an image processing apparatus according to a preferred embodiment of the present invention.

6 is a block diagram illustrating a file size control unit according to a preferred embodiment of the present invention.

7 is a block diagram illustrating an image processing apparatus according to a first embodiment of the present invention.

8 is a block diagram illustrating an image processing apparatus according to a second exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

310: image sensor

320: image processing device

330: image processing unit

340: JP encoder

350: File size control

360: memory

620: File size control

630: Counter

640: comparator

650: control signal generator

The present invention relates to an image processing method and apparatus, and more particularly, to an image processing method and apparatus capable of controlling a JPEG file size.

Image processing apparatuses are used in various digital processing apparatuses, such as digital cameras, mobile phones, and computers, and are particularly related to image compression technology. Image compression technology is often used as a JPEG (hereinafter referred to as `` JPEG '') in the case of a still image, MPEG (hereinafter referred to as 'MPEG') in the case of a video. Here, the JPEG standard ISO / IEC 10918 is the most popular still image compression format used today. The standard has the flexibility to choose between high quality photos with very high compression rates or moderate quality photos with very high compression ratios. Systems such as cameras and screens can be made inexpensively because of the simplicity of this technology. Generally, JPEG-compressed photos show no visual difference compared to the original. Creating the actual image is a cosine difference transform (DCT) and is applied after quantification to remove unwanted images.

When transmitting compressed data in a system using an actual J-CODEC, the clock frequency of a device to be transmitted may be different or the size of a data bus may be different. In this case, the first-in first-out (FIFO) (FIFO) (FIFO) to transfer the data, or a faster frequency clock is used for buffering. However, this method is dependent on the size of the image and high frequency components, and thus cannot be a fundamental problem-solving solution.

In order to solve such a transmission problem, according to the prior art, when compressing an image photographed with a digital still camera and storing it in a memory, the remaining portion of the memory is judged to change the q-factor, which is the largest part for determining the compression ratio. A certain number of images taken are recorded. In addition, according to another conventional technology, a method of maintaining the size of a JPEG file by automatically adjusting the q-factor by analyzing edge components of an image to be input to the JPEG encoder has been proposed.

However, these methods depend on the size of the image, and when transmitting compressed data, the size of the FIFO and the clock frequency depend on the size of the input image, so that the buffering memory or the use frequency should be changed according to the size of the image. have.

The present invention provides an image processing method and apparatus capable of controlling the JPEG file size by controlling a filter included in the image processing apparatus.

The present invention also provides an image processing method and apparatus capable of controlling a JPEG file size capable of preventing a buffering memory overflow by controlling a JPEG file size corresponding to a preset size by controlling a filter included in the image processing apparatus. do.

According to an aspect of the present invention, an image processing unit including a smoothing filter for converting high frequency components of image data into low frequency components, a JPEG encoder for compressing image data input from the image processing unit, and an amount of image data output from the JPEG encoder The image processing apparatus may include a file size control unit configured to measure and control the on / off of the smoothing filter of the image processor according to the measured amount of image data.

Here, the file size controller may operate the smoothing filter when the amount of image data is greater than a preset reference value, and may not operate the smoothing filter when the amount of image data is smaller than a preset reference value.

According to another aspect of the present invention, an image processing unit including a smoothing filter for converting high frequency components of image data into low frequency components, a JPEG encoder for compressing image data input from the image processing unit, and an amount of image data output from the JPEG encoder A counter for measuring a signal, a comparator for generating a control base signal by comparing the amount of image data measured by the counter with a preset reference value, and a filter for controlling on / off of the smoothing filter of the image processor in accordance with the control base signal input from the comparator An image processing apparatus including a control signal generator configured to generate a sub control signal may be provided.

Here, the image processing unit includes a Bayer filter unit for arranging the image data input from the image sensor in a Bayer pattern, an interpolation unit for interpolating the image data input from the Bayer filter, a gamma correction unit for gamma-correcting the image data interpolated in the interpolation unit, The apparatus may include a color corrector configured to color correct the image data input from the gamma corrector.

Here, at least one of the Bayer filter unit, the interpolation unit, the gamma correction unit, and the color correction unit may include a smoothing filter, and the smoothing filter may be a Gaussian filter.

Here, the filter unit control signal may be a control signal that operates the smoothing filter when the amount of the image data is greater than a preset reference value, and does not operate the smoothing filter when the amount of the image data is smaller than the preset reference value.

According to another aspect of the invention, the image processing unit for performing image processing on the image data input from the image sensor (image processing includes at least one of Bayer pattern arrangement, interpolation, gamma correction and color correction), from the image processing unit A smoothing filter unit having a plurality of smoothing filters for converting high frequency components of the input image data into low frequency components; a jpeg encoder for compressing the image data input from the smoothing filter unit; and an amount of image data output from the jpeg encoder And a file size controller for controlling on / off of the smoothing filter according to the measured amount of image data.

The file size control unit may include a counter for measuring the amount of image data output from the JPEG encoder, a comparator for generating a control base signal by comparing the amount of image data measured at the counter with a preset reference value, and a control base signal input from the comparator. Correspondingly, it may include a control signal generator for generating a filter control signal for controlling the on / off of the smoothing filter.

Here, the number of filter part control signals may be equal to the number of smoothing filters for converting a high frequency component of the smoothing filter part into a low frequency component.

Here, the filter unit control signal may be a control signal that operates the smoothing filter when the amount of the image data is greater than a preset reference value, and does not operate the smoothing filter when the amount of the image data is smaller than the preset reference value.

Here, the smoothing filter for converting a high frequency component of the image data included in the smoothing filter unit into a low frequency component may be a Gaussian filter.

According to another aspect of the invention, (a) the image processing step of the image processing unit for the image data (the image processing includes at least one of Bayer pattern arrangement, interpolation, gamma correction, color correction), ( b) compressing the processed image data by the JPEG encoder, and (c) outputting the compressed image data to the memory, wherein step (a) performs smoothing filtering, and smoothing filtering is performed by the JPEG compression. The present invention can provide an image processing method in which on / off is controlled by a filter control signal corresponding to an amount of image data output to a memory.

Here, the filter control signal may be a signal for controlling smoothing filtering when the amount of image data is greater than a preset reference value, and not performing smoothing filtering when the amount of image data is smaller than a preset reference value.

According to another aspect of the invention, (a) the image processing step of the image processing unit for the image data (the image processing includes at least one of Bayer pattern arrangement, interpolation, gamma correction, color correction), ( b) performing smoothing filtering on the processed image data by converting a high frequency component of the image data into a low frequency component in a smoothing filter; (c) compressing the processed image data by a JPEG encoder, (d) And outputting the compressed image data to the memory, wherein the smoothing filter proposes an image processing method in which on / off is controlled by a filter control signal corresponding to the amount of image data compressed by the JPEG encoder and output to the memory. can do.

In addition, the image processing method according to the present invention comprises the steps of (e) measuring the amount of image data output from the JPEG encoder, (f) generating a control base signal by comparing the measured image data amount with a preset reference value, (g) generating a filter part control signal for controlling on / off of the smoothing filter corresponding to the control elementary signal.

Here, the number of filter part control signals may be equal to the number of smoothing filters for converting a high frequency component of the smoothing filter part into a low frequency component.

In addition, the image processing method according to the present invention comprises the step of (h) the filter control signal to operate the smoothing filter if the amount of the image data is greater than the preset reference value, and if the amount of the image data is less than the preset reference value does not operate the smoothing filter It may further include.

Hereinafter, a preferred embodiment of a JPEG file size controllable image processing method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings, and in the following description with reference to the accompanying drawings, the same configuration irrespective of the reference numerals Elements are given the same reference numerals and redundant descriptions thereof will be omitted. In addition, prior to the detailed description of the preferred embodiments of the present invention will be described with respect to JPEG encoding and decoding.

FIG. 1 is a block diagram schematically illustrating a typical JPEG encoder, and FIG. 2 is a block diagram illustrating a typical JPEG decoder. If the JPEG codec is a device for processing a digital image, it may be used in a digital camera, a mobile communication terminal, a computer, a game terminal, and the like.

Referring to FIG. 1, an original image data 110, a JPEG encoder 120, and a compressed data 160 are illustrated, and the JPEG encoder 120 includes a discrete cosine transform unit (FDCT). 130, the quantizer 140, and the entropy encoder 150, the quantizer 140 and the entropy encoder 150 are tables, respectively. (Table Specification) (145, 155) and performs a function.

2, the compressed data 160, the JPEG decoder 210, and the reconstructed image 250 are illustrated, and the JPEG decoder 210 includes an entropy decoder 220, De-Quantizer 230 and a discrete cosine transform (IDCT: Inverse Discrete Cosine Transformation (240)) includes an entropy decoder (Entropy Decoder) 220 and De-Quantizer ( 230 is combined with Table Specification 225 and 235 to perform a function.

In general, the JPEG encoder 120 divides the original image data 110 into 8x8 blocks, and performs discrete cosine transform 130 on each block. Thereafter, quantization 140 is performed on the input image data, the coefficients are coded, headers are stored, and the image data is stored according to a predetermined format. Then, the JPEG decoder reads the file, decodes the image data, performs inverse quantization, performs discrete cosine transform (IDCT) on each block, and reconstructs the original image.

Here, when the lossless compression method is applied, discrete cosine transform 130 is performed on the image data, lossy compression is performed while passing through the quantizer 140, and entropy coding, which is a lossless compression method, is about 2 times the image. More compression is obtained. Therefore, the compression ratio is largely determined depending on the usage form of the quantizer 140. Since the technology related to the Jpec codec is a natural technology to those skilled in the art, detailed description thereof will be omitted.

3 is a block diagram illustrating an image processing apparatus including a smoothing filter according to an exemplary embodiment of the present invention. Referring to FIG. 3, an image sensor 310, an image processing apparatus 320, a memory 360, and a baseband or camera control processor (CCP) for capturing an image of an object are illustrated. The device 320 includes an image processor 330, a JPEG encoder 340, and a file size controller 350.

The image data input from the image sensor 310 passes through the image processor 330 and is then compressed by the JPEG encoder 340. When transmitting compressed data to the baseband or camera control processor (CCP) 370, a memory 360 capable of buffering may be used due to a mismatch between the frequency and the data bus.

Here, the file size control unit 350 measures the amount of image data output from the JPEG encoder 340 and inputs to the memory 360, and on / off the smoothing filter of the image processing apparatus according to the measured amount of image data. To control. That is, according to the present invention, the filter of the image processor 330 is automatically changed by analyzing the state information of the memory 360 with an additional circuit called the file size controller 350. This operation smoothes the high frequency components input from the image sensor 310, and as a result, adjusts the amount of data output from the JPEG encoder 340, and thus the amount of compressed data loaded into the buffering memory 360. Remains constant.

The file size control unit 350 operates the smoothing filter when the amount of image data output from the JPEG encoder 340 and input to the memory 360 is greater than a preset reference value, and is output from the JPEG encoder 340 to output the memory 360. If the amount of the image data inputted at) is smaller than the preset reference value, the size of the output JPEG file can be adjusted uniformly by not operating the smoothing filter. Here, the preset reference value may be set to the image processing apparatus 320 by default or may be set directly by the user using the user interface. In this case, the user may adjust the reference value according to the size of the memory 360. For example, when the size of the memory 360 is small, the user may reduce the reference value of the amount of image data to reduce the burden of the memory 360. Can be.

In addition, the image processing apparatus 360 may include a preset number of smoothing filters, and the smoothing filter may be included in a component included in the image processor 330 or may be implemented as a separate filter. This will be described in detail with specific embodiments.

4 is a block diagram illustrating an image processing unit and a Jpeg encoder for processing image data input from an image sensor according to an exemplary embodiment of the present invention. Referring to FIG. 4, an image sensor 310, an image processor 330, and a JPEG encoder 340 are shown. The image processor 330 includes a Bayer filter 331 and an interpolation unit. ) 333, a gamma correction unit 335, a color correction unit 337, and a format converter (RGB to YCbCr Converter) 339.

The Bayer filter 331 arranges the points receiving the respective brightnesses of RGB on the two-dimensional plane in order to collect the brightness and the color of the object and make an image composed of the points. When placing these dots, the Bayer pattern is arranged using a Bayer color filter that assigns 50% of the most sensitive green to the human eye and 25% of red and blue.

The interpolation unit 333 interpolates the image data, and performs gamma correction on the image data interpolated by the gamma correction unit 335 and the color correction unit 337. Perform color / luminance correction. The order of performing such interpolation and correction may be interchanged depending on the situation of the technology implementation. The RGB to YCbCr Converter 339 then converts the image data stored as RGB information into the YUV format to produce smaller data. Since the components of the image processor 330 are general contents to those skilled in the art, detailed description thereof will be omitted.

Here, at least one of the Bayer filter 331, the interpolation unit 333, the gamma correction unit 335, and the color correction unit 337 includes a smoothing filter. do. Each smoothing filter converts high frequency components of the image data into low frequency components, and the image data passing through the smoothing filter is reduced in size.

5 is a Gaussian filtering flowchart performed in an image processing apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 5, a 3-tap Gaussian filter 510 and a pixel 520 are illustrated as a smoothing filter, and Equation 530 in which the pixel 520 passes through the 3-tap Gaussian filter 510 is converted. Illustrated illustratively. The third pixel may be multiplied with the second and third pixels of the 3-tap Gaussian filter 510 and then summed with the second and fourth pixels to be divided into four pixel values. That is, the 3-tap Gaussian filter 510 is applied to pixels divided into 1, 2, 3, 4, and 5 to smooth the high frequency components to increase the compression ratio of the Jpeg encoder to increase the compression rate of the JPEG output file. The size can be kept constant.

Here, only the Gaussian filter is illustrated as the smoothing filter, but other filters such as a Laplacian filter may also be applied to the present invention as long as the filter can serve as a smoothing filter.

6 is a block diagram illustrating a file size control unit according to an exemplary embodiment of the present invention. Referring to FIG. 6, a memory 610 and a file size controller 620 are illustrated, and the file size controller 620 includes a counter 630, a comparator 640, and a control signal generator 650.

The memory 610 receives compressed image data from the JPEG encoder, and the counter 630 measures the size / amount of image data output from the JPEG encoder and input to the memory 610.

The comparator 640 generates a control base signal by comparing the amount of image data measured by the counter 630 with a preset reference value. The control basic signal may be generated in various formats. Referring to FIG. 6, the control basic signal is classified into four types of 'almost full', 'almost empty', 'full' and 'empty'. This classification may be set by default in the file size control unit 620 or directly by the user through the user interface.

The control signal generator 650 generates a filter control signal for controlling on / off of the smoothing filter associated with the image processor in accordance with the control base signal input from the comparator 640. The control base signal is a base signal for generating the filter unit control signal, and the number may not be the same. That is, when there are four control base signals, the filter unit control signals may be determined irrespective of four.

The number of filter control signals may be equal to or less than the number of smoothing filters. That is, when the number of smoothing filters is four, the number of filter control signals is four or less, and each filter control signal may control on / off of a corresponding smoothing filter.

In the above description, a system configuration diagram of an image processing method and apparatus for controlling a JPEG file size according to the present invention has been described in general. Hereinafter, with reference to the accompanying drawings, an image of a JPEG file size control according to the present invention may be described. The processing method and apparatus thereof will be described with reference to specific embodiments. Embodiments according to the present invention can be broadly classified into two types. First, a method of controlling a jpeg file size using a plurality of smoothing filters included in each component of an image processor, and second, a plurality of separately provided smoothing filters are provided. It is divided into the method of controlling the JPEG file size by using. It demonstrates in order below.

FIG. 7 is a block diagram illustrating an image processing apparatus for controlling a JPEG file size using a plurality of smoothing filters included in each component of an image processing unit according to a first exemplary embodiment of the present invention. Referring to FIG. 7, the counter 730 checks the degree of accumulation of data output from the JPEG encoder 340 and input to the buffer memory 710 in the FIFO. The comparator 740 refers to the register setting value for file size adjustment, and controls basic signals (e.g. 'almost full', 'almost empty', 'full' and 'empty'). And the like). The control signal generator 750 receives the control base signal from the comparator 740 and outputs a filter control signal (for example, 1, 2, 3, 4).

Here, the first filter part control signal 1 controls the smoothing filter of the Bayer filter 331, the second filter part control signal 2 controls the smoothing filter of the interpolation part 333, and the third filter part. The control signal 3 controls the smoothing filter of the color corrector 337, and the fourth filter control signal 4 controls the smoothing filter of the gamma corrector 335. The combination between each filter part control signal and the smoothing filter can be arbitrarily determined. The combination between the filter unit control signals may vary depending on the control base signal. For example, when the comparator 740 determines that the amount / size of the image data is much larger than a preset value, the comparator 740 generates 'full' among the control base signals and outputs the 'full' to the control signal generator 750. The control signal generator 750 may receive a signal of 'full', generate a signal for operating all smoothing filters, and transmit the signal to the image processor 330 to maintain a constant size of the output JPEG file. Here, when there are four smoothing filters and four filter control signals, there are two methods of turning on / off each filter control signal. Thus, a total of 16 smoothing filters are operated.

FIG. 8 is a block diagram illustrating an image processing apparatus for controlling a JPEG file size using a plurality of separately provided smoothing filters according to a second exemplary embodiment of the present invention. Hereinafter, the differences from the first embodiment will be mainly described.

The smoothing filter unit 800 receives the image data from the format converter (RGB to YCbCr Converter) 339, filters the image data, and outputs the image data to the JPEG encoder 340. The smoothing filter unit 800 includes a plurality of smoothing filters for converting high frequency components of the image data into low frequency components. The smoothing filter may be provided with a plurality of filters of the same type, or may be provided with various filters of different types. For example, a plurality of Gaussian filters may be provided, or a Laplacian filter and a Gaussian filter, which may serve as smoothing filters, may be provided with various combinations. The filter unit control signal output to the control signal generator 750 controls on / off of each smoothing filter included in the smoothing filter unit 800.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

As described above, the image processing method and apparatus for controlling the JPEG file size according to the present invention can control the JPEG file size by controlling a filter included in the image processing apparatus.

In addition, the Jpek file size controllable image processing method and apparatus according to the present invention may prevent the buffering memory overflow by controlling the Jpek file size corresponding to a preset size by controlling a filter provided in the image processing device. .

Claims (15)

An image processor including a smoothing filter for converting high frequency components of the image data into low frequency components; A JPEG encoder for compressing image data input from the image processor; And And a file size controller configured to measure an amount of image data output from the JPEG encoder and to control on / off of the smoothing filter of the image processor in accordance with the measured amount of image data. The method of claim 1, And the file size control unit operates the smoothing filter when the amount of the image data is greater than a preset reference value, and does not operate the smoothing filter when the amount of the image data is smaller than a preset reference value. An image processor including a smoothing filter for converting high frequency components of the image data into low frequency components; A JPEG encoder for compressing image data input from the image processor; A counter for measuring the amount of image data output from the JPEG encoder; A comparator configured to generate a control base signal by comparing the amount of image data measured by the counter with a preset reference value; And And a control signal generation unit configured to generate a filter unit control signal for controlling on / off of the smoothing filter of the image processing unit in response to the control basic signal input from the comparator. The image processing apparatus of claim 3, wherein the image processor A Bayer filter unit for arranging image data input from the image sensor in a Bayer pattern; An interpolation unit which interpolates the image data input from the Bayer filter; A gamma correction unit which gamma-corrects the image data interpolated by the interpolation unit; And Including a color correction unit for color correction of the image data input from the gamma correction unit, And at least one of the Bayer filter, the interpolator, the gamma corrector, and the color corrector comprises a smoothing filter. The method of claim 3, The filter unit control signal may be a control signal that operates the smoothing filter when the amount of the image data is greater than a preset reference value, and does not operate the smoothing filter when the amount of the image data is less than a preset reference value. Device. An image processor which performs image processing on image data input from an image sensor, the image processing including at least one of Bayer pattern arrangement, interpolation, gamma correction, and color correction; A smoothing filter unit having a plurality of smoothing filters for converting high frequency components of the image data input from the image processing unit into low frequency components; A JPEG encoder for compressing the image data input from the smoothing filter unit; And And a file size control unit for measuring the amount of image data output from the JPEG encoder and controlling on / off of the smoothing filter in accordance with the measured amount of image data. The method of claim 6, The file size control unit A counter for measuring the amount of image data output from the JPEG encoder; A comparator configured to generate a control base signal by comparing the amount of image data measured by the counter with a preset reference value; And And a control signal generator for generating a filter unit control signal for controlling on / off of the smoothing filter in response to the control basic signal input from the comparator. The method of claim 7, wherein The number of the filter unit control signal is the same as the number of the smoothing filter for converting the high frequency component provided in the smoothing filter unit to a low frequency component. The method of claim 7, wherein The filter unit control signal may be a control signal that operates the smoothing filter when the amount of the image data is greater than a preset reference value, and does not operate the smoothing filter when the amount of the image data is less than a preset reference value. Device. (a) the image processing unit performing image processing on the image data, the image processing including at least one of Bayer pattern arrangement, interpolation, gamma correction, and color correction; (b) a JPEG encoder compressing the image processed image data; And (c) outputting the compressed image data to a memory; The step (a) performs smoothing filtering, wherein the smoothing filtering is controlled on / off by a filter control signal corresponding to the amount of image data compressed and output to the memory. The method of claim 10, The filter unit control signal is a signal for controlling the smoothing filtering when the amount of the image data is greater than a preset reference value and not performing the smoothing filtering when the amount of the image data is smaller than a preset reference value. Image processing method. (a) the image processing unit performing image processing on the image data, wherein the image processing includes at least one of Bayer pattern arrangement, interpolation, gamma correction, and color correction; (b) performing smoothing filtering on the image processed image data by converting a high frequency component of the image data into a low frequency component in a smoothing filter; (c) a JPEG encoder compressing the smoothed filtered image data; And (d) outputting the compressed image data to a memory; And the smoothing filter is controlled on / off by a filter control signal corresponding to the amount of image data compressed by the JPEG encoder and output to the memory. The method of claim 12, (e) measuring the amount of image data output from the JPEG encoder; generating a control base signal by comparing the measured image data amount with a preset reference value; And and (g) generating a filter unit control signal for controlling on / off of the smoothing filter in correspondence with the control basic signal. The method of claim 12, The number of the filter unit control signal is the same as the number of the smoothing filter for converting the high frequency component provided in the smoothing filter unit to a low frequency component. The method of claim 12, (h) the filter unit control signal may further include operating the smoothing filter if the amount of the image data is greater than a preset reference value, and disabling the smoothing filter if the amount of the image data is less than a preset reference value. An image processing method characterized by the above-mentioned.

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