KR20090114971A - Method and device for confirming compression rate of compressed image - Google Patents

Abstract

PURPOSE: A compression rate verifying method and device for a compressed image is provided to verify the compression ratio of the image with the compressed image itself. CONSTITUTION: A compression rate-data size output unit(110) calculates the compression ratio-data size. The compression ratio-data size is included the data size information according to the compression ratio. A compression rate calculator(150) searches the compression ratio value having the same size as the 100% compression ratio based on the compression ratio-data size. A compression rate-data size storage unit(130) stores the calculated compression ratio-data size.

Description

Method and device for confirming compression rate of compressed image}

TECHNICAL FIELD The present invention relates to image compression, and more particularly, to a method and apparatus for confirming a compression ratio of a compressed image.

With the development of data communication networks and transmission technologies, images are used as an important means of conveying information along with text. In particular, as digital cameras become more popular, users can freely upload or download images to a web server, and in the fields of electronic commerce, the image of a product is becoming the most important information about the product.

Image is one of the largest data occupying the storage space of the server and various storage media, and the study of the compression of the image is continuously made.

Image compression is classified into lossy compression and lossless compression, and lossy compression refers to a method of compressing the data information of an image when the data information of the image is lost. Lossless compression is mainly used for lossless image data, such as medical imaging.

The most common method of image compression is JPEG (Joint Photographic Expert Group), which supports both lossy and lossless compression, and lossy compression is mainly used for efficient use of storage space in general web and portable devices. .

Compression of the original image can be done through an image editing application such as Photoshop, where a compression scheme such as JPEG supports the ability to adjust the compression rate directly. The higher the compression rate, the smaller the data size of the image, but the image will be corrupted, resulting in a lower quality than the original image.

However, the human eye can distinguish only 7.5 million colors, and almost half of the 16-bit color of 1677 million colors cannot be recognized. For example, Photoshop or other image editing applications compress the image with a low compression rate to avoid damaging the original image unless you specify otherwise when converting the image to JPEC or other compression algorithms.

In addition, the digital camera also compresses the captured image, but converts the image with a low compression rate in consideration of the deterioration of the image. Therefore, it was not possible to efficiently use the limited storage space of the digital camera. It was also common to compress at relatively low compression rates to prevent image corruption.

As such, the compression rate of the image varies depending on the device using the image (e.g., a web server, a digital camera, etc.) and the purpose of use, and a method of confirming the compression rate of the image when using the compressed image is required. Was done. For example, if the compressed image received from the consumer or the advertiser has a lot of damages when the naked image is viewed by the naked eye, the shopping mall operator may check the compression rate of the image and specify the compression rate to be uploaded later. As another example, when it is necessary to restore a compressed image due to poor image quality, the compression ratio of the image may be used as important information as reconstruction information.

Conventionally, by compressing and using an original image in a format such as JPEG, a user who acquires the image cannot know the compression rate of the image by what percentage without compressing the information.

Accordingly, the present invention has been made to solve the above-described problem, and to provide a method and apparatus for confirming the compression ratio of a compressed image without additional compression information.

Other objects of the present invention will become more apparent through the preferred embodiments described below.

According to an aspect of the present invention, the method comprises: calculating a compression ratio-data size that is data size information according to a compression ratio for a predetermined interval for an interval corresponding to an original image that has already been lost compressed; Retrieving a compression rate value having a size equal to 100% compression rate based on the compression rate-data size; And resultantly processing the retrieved compression ratio value as a lossy compression ratio of the original image, and a recording medium having recorded thereon a program for executing the method.

The method may further include determining whether the original image is lossy compressed using the compression rate-data size. The determining of whether the original image is in a lossy compression state may include determining whether there is an area where the size decreases sequentially as the compression rate decreases based on the compression rate-data size. .

According to another aspect of the present invention, there is provided a compression rate-data size output unit for calculating a compression rate-data size, which is data size information according to a compression ratio for a predetermined interval for an interval corresponding to an original image that has already been lost compressed; And a compression ratio calculating unit for retrieving a compression ratio value having a size equal to 100% compression ratio based on the compression ratio-data size and processing the result as a lossy compression ratio of the original image.

The apparatus may further include a compression rate data size storage unit for storing the calculated compression rate data size.

The compression rate calculator may determine whether the original image is lossy compressed using the compression rate-data size, and search for the compression rate value when it is determined that the original image is lossy compressed. have.

In addition, determining whether the original image is in a lossy compressed state may determine whether there is an area where the size decreases sequentially as the compression rate decreases based on the compression rate-data size.

According to the method and apparatus for confirming the compression rate of a compressed image according to the present invention, the compression rate can be confirmed only by the compressed image itself without additional compression information.

In addition, according to the present invention, it is possible to check the compression ratio of the compressed image, there is an advantage that can be importantly used as reconstruction information when the need to restore the original image.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and in describing the present invention with reference to the accompanying drawings, the same or corresponding elements are denoted by the same reference numerals regardless of the reference numerals, and duplicates thereof. The description will be omitted.

Before describing the method and apparatus for checking the image compression rate of the present invention, the image compression will be briefly described.

Image compression is classified into loss compression and lossless compression. The most common image compression method is JPEG (Joint Photographic Expert Group), and gif and tiff.

Lossless compression refers to a method of compressing the data information of an image while the original information is lost. Lossless compression refers to a compression in which the amount of information does not change when the image is compressed.

In general, lossy compression based on DCT (Discrete Cosine Transform) is used for image compression, and lossless compression is used for compressing important image data such as medical images.

The video image comprises a minimum unit called pixels to form a screen. The number of pixels that make up the screen determines the resolution, such as 1024 * 768 or 800 * 640.

JPEG, the most representative of the image compression methods, compresses information using an 8 * 8 block matrix.

8 is a diagram illustrating an example of a matrix obtained by converting an 8 * 8 block matrix of the present video into a DCT.

The DCT (Discrete Cosine Transform) is performed on an 8 * 8 block matrix. Referring to FIG. 8, when the DCT operation is performed, large numbers are attracted to the upper left corner. The number of dogs is called the high frequency value. In particular, low frequency values and numbers in the vicinity are important information for determining the brightness of the entire block.

When the DCT change is performed, quantization is performed to reduce the overall amount of data. 9 is a diagram illustrating an example of performing quantization in JPEG. As shown in FIG. 9, an arbitrary matrix called a quantization matrix is used in the quantization process. At this time, information loss occurs as small values are changed to 0.

When the quantization process is performed, bitstreams are compressed using zigzag scanning and Huffman coding tables.

10 illustrates an example of performing zigzag scanning and Huffman coding in JPEG compression.

Referring to FIG. 10, an integer sequence made by zigzag scanning is converted into a binary number, and then an 8 * 8 block matrix is transformed into a combination of several 0's and 1's using Huffman coding using adjacent value characteristics and probabilities. The decoding of JPEG proceeds in the reverse order of the encoding process described above.

JPEG compression and other kinds of image compression schemes as described above can adjust the compression rate. Image editing programs such as Photoshop and ACDSee support compressing the original image while adjusting the compression rate. Image capture devices such as digital cameras also compress and compress the captured image.

Hereinafter, a method of confirming a compression ratio of an image compressed by various compression methods such as JPEG and GIF will be described.

1 is a functional block diagram showing the configuration of an image compression ratio checking apparatus according to an embodiment of the present invention, Figure 2 is a graph showing a typical compression ratio-data size relationship of the uncompressed image, Figure 3 4 is a graph illustrating a compression rate-data size relationship of a compressed image according to an embodiment of the present invention, and FIG. 4 is a diagram illustrating a data format stored in a compression rate-data size storage unit according to an embodiment of the present invention. .

Referring to FIG. 1, the apparatus for checking an image compression rate according to the present embodiment includes a compression rate-data size output unit, a compression rate-data size storage unit 130, and a compression rate calculation unit 150. It may include a compression determination unit 152 and the compression rate confirmation unit 154.

The compression rate-data size output unit 110 outputs size information corresponding to the compression rate for the image to be compressed. That is, the compression rate-data size output unit 110 outputs a data size corresponding to each compression rate. For example, when the compression ratio is 99%, the image data size according to the compression ratio of 1% intervals can be output as in the case of 98%, and the compression ratio section can be variously set as necessary to those skilled in the art. Will be self explanatory.

Here, the compression ratio of the compression rate-data size according to the present embodiment refers to the ratio of the size of the compressed state to the original size of the image. For example, in the case of the compression ratio 90, the size of 90% of the original image size is determined. It is compressed to have. That is, when the original image has a size of 100, the image according to the compression ratio 90% has a size of 90. Hereinafter, when the compression rate is close to 100%, it means that the compression rate is low, and when the compression rate is close to 1%, it means that the compression rate is high.

According to an embodiment of the present invention, the compression rate-data size output unit 110 outputs the data size according to the compression rate from 100% to 1% at 1% intervals. The wider and more detailed the compression rate section and interval, the more accurate the compression rate can be confirmed. However, since it requires a lot of processing time, it is preferable to set the compression section and interval in consideration of the processing time and accuracy.

As shown in FIG. 2, a compression rate-data size relationship of an uncompressed image has a higher data size at a lower compression rate and a lower data size at a higher compression rate.

On the contrary, referring to FIG. 3, the data size decreases as the compression rate decreases based on the 95% compression rate, and the data size is smaller than the 95% compression rate.

As such, when the data size does not increase as the compression rate decreases, the image may be determined to be a lossy compressed image.

The apparatus for checking the image compression rate according to the present embodiment estimates the corresponding loss compression rate by using the compression rate-data size information of the lossy compressed image having the graph model as shown in FIG. 3. A method of estimating the lossy compression ratio using the compression rate-data size information of the lossy compressed image by the compression rate calculator 150 will be described later.

The compression rate-data size storage unit 130 stores data size information according to the compression rate output from the compression rate-data size output unit 110.

When the image compression rate confirmation method according to the present invention is processed in a computer device, the compression rate-data size information may be stored in a volatile memory such as RAM. When processed in portable terminals such as digital cameras and mobile communication terminals, the compression rate-data size information may be stored in memory means such as RAM or flash memory.

An example of the data format stored in the compression rate-data size storage 130 is shown in FIG. 4. Referring to FIG. 4, the data stored in the compression rate-data size storage unit 130 includes a compression rate field 400 and a size field 410, and data size information corresponding to each compression rate is recorded.

The compression rate and the data size information stored in the compression rate-data size storage unit 130 are used for data processing in the compression rate calculation unit 150.

The compression rate calculation unit 150 functions to calculate a corresponding loss compression rate using the compression rate-data size information of the lossy compressed image stored in the compression rate-data size storage unit 130.

The compression determining unit 152 of the compression rate calculating unit 150 checks the compression rate-data size information of the lossy compressed image stored in the compression rate-data size storage unit 130 to determine whether the image is already lossy compressed. To judge. As described above, the determination method is a section in which the data size decreases as the compression rate decreases, such that the data size at 100% compression rate as shown in FIG. 3 is smaller than the data size at 95% compression rate. If present, the image can be recognized as compressed. On the contrary, when the compression rate-data size information of the conventional model as shown in FIG. 2 is included, the image may be recognized as a lossless uncompressed image.

The compression rate checking unit 154 calculates a compression rate of the corresponding image when it is determined that the image is a compressed image as a result of the determination in the compression determining unit 152. The compression rate checking unit 154 searches for a compression rate having the same size as the data size at 100% compression rate by using the information stored in the compression rate-data size storage unit 130, and calculates the retrieved compression rate as the lossy compression rate of the corresponding image. Output

Referring to FIG. 3 again for convenience of understanding, it can be seen that the data size is 44 when the compression ratio is 100%, and the compression ratio having the same data size is 75%. Therefore, the compression rate confirming unit 154 recognizes that the image having the compression rate-data size according to FIG. 3 is lost and compressed at 75%, and outputs the 75% compression rate of the corresponding image.

5 and 6 are graphs showing a compression rate-data size relationship in which any image is compressed at 10% and 20% according to each embodiment of the present invention.

Referring to FIG. 5, it can be seen that the data size according to the compression ratio of 100 is 199, and the compression rate having the same data size along the horizontal axis is 10%. Accordingly, it can be seen from FIG. 5 that the image is compressed at 10%. That is, as described above, the compression rate calculator 150 may check the compression rate of the corresponding image using FIG. 5.

 In addition, referring to FIG. 6, it can be seen that the data size according to the compression rate of 100% is 305 and the compression rate having the same data size along the horizontal axis is 20%, so that the compression rate of the corresponding image is 20%.

7 is a flowchart illustrating the overall flow of the image compression ratio checking method according to an embodiment of the present invention.

Referring to FIG. 7, data size information according to a compression ratio of an original image for identifying a compression ratio is calculated (S710). As described above, the data size information according to the compression rate may be calculated at intervals of 1% to 1% to 100% compression rate, and the data size information according to the compression rate for each finer or larger interval and interval may be obtained. It can also be calculated.

When the compression rate-data size information is calculated, the information is stored in a memory means such as a RAM or a flash memory (S720).

When the compression rate-data size information is calculated, it is determined whether the compression rate can be confirmed image (S730). That is, as described above, a phenomenon in which a data size decreases despite a small compression ratio in a specific section does not occur in the compression ratio-data size information, and is proportional to the size of the compression ratio as shown in FIG. 2. If the size is increased, it is determined that the original image is not lossy compressed and the compression rate checking operation is terminated (S740).

If it is determined that the image is a compressed image, a compression ratio value having the same value as the data size according to the 100% compression ratio is searched based on the stored compression ratio-data size information (S750).

The retrieved compression ratio value is output as a lossy compression ratio of the corresponding image (S760).

Here, unlike the present embodiment, step S730 and step S740 may not be performed, and step S750 may be performed immediately after step S720. After all, if the original image is not compressed, if the compression ratio having the same data size as the 100% compression ratio does not exist, the corresponding compression ratio is 100%.

The method of the present invention as described above may be implemented in a program and stored in a computer-readable recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.).

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.

1 is a functional block diagram showing the configuration of an image compression ratio checking apparatus according to an embodiment of the present invention.

2 is a graph illustrating a typical compression rate-data size relationship of an uncompressed image.

3 is a graph illustrating a compression rate-data size relationship of a compressed image according to an embodiment of the present invention.

4 illustrates a data format stored in a compression rate-data size storage unit according to an embodiment of the present invention.

5 and 6 are graphs showing a compression rate-data size relationship in which any image is compressed at 10% and 20% according to each embodiment of the present invention.

7 is a flow chart showing the overall flow of the image compression ratio confirmation method according to an embodiment of the present invention.

8 is a diagram showing an example of a matrix obtained by converting an 8 * 8 block matrix of the present video into a DCT.

9 shows an example of performing quantization in JPEG.

10 shows an example of performing zigzag scanning and Huffman coding in JPEG compression.

Claims (8)

Calculating a compression ratio-data size, which is data size information according to a compression ratio for each interval for an interval corresponding to the original image which has already been lost compressed; Retrieving a compression rate value having a size equal to 100% compression rate based on the compression rate-data size; And And processing the retrieved compression ratio value as a lossy compression ratio of the original image. The method of claim 1, And determining whether the original image is in a lossy compressed state by using the compression rate-data size. The method of claim 2, The determining of whether the original image is in a lossy compressed state may include determining whether there is an area where the size decreases sequentially as the compression rate decreases based on the compression rate-data size. How to check the compression rate. A recording medium in which a combination of instructions for performing the method of any one of claims 1 to 3 is tangibly embodied and in which a program readable by a digital information processing apparatus is recorded. A compression ratio-data size output unit for calculating a compression ratio-data size, which is data size information according to compression ratios for a predetermined interval, for a predetermined interval corresponding to the original image which has already been compressed; And And a compression ratio calculation unit for retrieving a compression ratio value having a size equal to 100% compression ratio based on the compression ratio-data size and processing the result as a lossy compression ratio of the original image. The method of claim 5, And a compression ratio-data size storage unit for storing the calculated compression ratio-data size. The method of claim 5, The compression rate calculation unit, An apparatus for determining an image compression ratio using the compression rate-data size to determine whether the original image is in a lossy compression state and retrieving the compression ratio value when it is determined that the original image is in a lossy compression state . The method of claim 7, wherein Determining whether or not the original image is in a lossy compression state is based on the compression rate-data size, and determining whether there is an area where the size decreases sequentially as the compression rate decreases. Confirmation device.

Images