JP2006270673A - Circuit for detecting image region - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an circuit for detecting image region, capable of automatically detecting effective region in an image for extracting information for the purpose of carrying out correction processing, and an ineffective region in the image that does not extract information, in response to the state of the image and of coping with various images. <P>SOLUTION: The image region detection circuit is provided with a counting circuit for counting the number of pixels, received in the scanning order of the image; a comparison circuit for sequentially comparing the difference in the signal levels between two consecutive pixels in the scanning order with a first reference value and outputting a comparison result, denoting whether the difference from the signal levels between the two pixels is the first reference value or smaller; a storage circuit for storing the result of the comparison, in cross-reference with the count of the counting circuit; and a detection circuit that when a difference of the signal levels between two pixels is the first reference value or smaller and the pixels are consecutive for a second reference value or larger, the positional information of the first pixel of the pixels and the number of consecutiveness are calculated to detect the effective region and the ineffective region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image area detection circuit that detects an effective area in an image from which information for performing correction processing according to the state of an image is extracted and an invalid area in an image from which information is not extracted.

  For example, if the image is dark overall, it can be corrected to a bright overall image by increasing the gain. However, even if the image is entirely dark, if the gain is simply increased when a very bright part is partially included, the bright part is crushed. For this reason, in order to perform appropriate correction on the image, the correction process is changed according to the state of the image.

  In order to detect the state of an image, information such as average luminance (APL: Average Picture Level), maximum luminance, and minimum luminance is extracted from the image. Based on this information, the image is an image that is an overall bright image, an overall dark image, or an average dark image, but has a very bright area. By determining the state, an appropriate correction process can be determined.

  However, for example, when watching a movie on a television, the display aspect ratio is different from that of a normal television program, and there may be a strip-shaped black display region (invalid region) extending horizontally from top to bottom of the television screen. However, if the black display area is included in the effective area and information is extracted, correct information cannot be obtained. For this reason, it has been proposed to extract the information by dividing the image into a plurality of areas to eliminate the influence of such information in the invalid area.

  As an example, there is a technique disclosed in Patent Document 1. In Patent Document 1, when detecting the peak level, the average level, and the black level of a luminance signal in a video display device, the image display device is divided into two or more areas of a central part and a peripheral part of the screen, It is disclosed that detection is performed in an area excluding the area, or detection is performed by increasing the weight of the central area as compared with the peripheral area.

Japanese Patent Laid-Open No. 5-224461

  However, in the method of Patent Document 1, since the division range of the screen region is fixed, only information on the same region can always be acquired, and various images cannot be handled. In addition, there is a problem that optimal correction cannot be performed when the entire screen is an effective area.

  An object of the present invention is to solve the problems based on the above-described conventional technology and automatically detect an effective area in an image for extracting information for performing correction processing according to an image state and an invalid area in an image from which information is not extracted. It is an object of the present invention to provide an image region detection circuit that can detect and correspond to various images.

To achieve the above object, the present invention detects an effective area in the image from which information for performing correction processing according to the state of the image is extracted, and an invalid area in the image from which the information is not extracted. An image area detection circuit comprising:
A count circuit that counts the number of pixels input in the scan order of the image;
The difference in signal level between two pixels that are consecutive in the scan order is sequentially compared with the first reference value to indicate whether the difference in signal level between the two pixels is equal to or less than the first reference value. A comparison circuit for outputting a comparison result;
A storage circuit for storing the comparison result in association with the count value of the count circuit;
When a comparison result associated with the count value is input and a pixel whose difference in signal level between the two pixels is equal to or less than the first reference value continues for a second reference value or more, the first The present invention provides an image region detection circuit comprising: a detection circuit for detecting the effective region and the invalid region by calculating the position information and the number of consecutive pixels.

Here, the storage circuit stores a comparison result associated with the count value over a plurality of frames of images,
It is preferable that the detection circuit detects the effective area and the invalid area based on position information and a continuous number of the first pixel over the images of the plurality of frames.

  Furthermore, it is preferable that a switching circuit for appropriately switching the first and second reference values is provided based on attribute information indicating what kind of signal the image is.

  Since the image area detection circuit of the present invention can automatically detect the effective area and the invalid area in the image, the image area detection circuit can be used to perform correction based on the pixels in the effective area. Such an image can always be appropriately corrected.

  Hereinafter, an image region detection circuit of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

  FIG. 1 is a schematic diagram of an embodiment showing a configuration of an image area detection circuit of the present invention. An image area detection circuit 10 shown in FIG. 1 performs correction processing according to the state of an image in order to perform appropriate correction on an image displayed on a display or an image recorded on a recording medium. An effective area in an image from which information is extracted and an invalid area in an image from which information is not extracted are detected. A comparison circuit 12, a count circuit 13, a storage circuit 14, a detection circuit 16, and a first reference The register 11 holds a value and the register 15 holds a second reference value.

  The comparison circuit 12 and the count circuit 13 are inputted with image signals of each frame (screen) in the scanning order of the pixels. The count circuit 13 is reset for each frame, counts the number of pixels input in the scan order, and outputs the count value to the storage circuit 14. The comparison circuit 12 sequentially compares the signal level difference (difference) between two pixels that are consecutive in the scan order with the first reference value held in the register 11 for all the pixels included in the image of the frame. Output the comparison result. The comparison result indicates whether or not the difference in signal level between the two pixels is equal to or less than the first reference value held in the register 11. In the case of this embodiment, if the difference in signal level between two consecutive pixels is less than or equal to the first reference value, “0” is set as the bit signal, and if the difference is greater than the first reference value, “1” is set as the bit signal. "" Is preferable because it has the advantage of reducing the storage capacity.

  Here, for example, when an image of one frame is composed of m pixels × n lines, the scan is sequentially performed for m pixels in the first line from the left pixel to the right pixel, and then, Then, the scanning is performed in the same manner after moving to the second line. Similarly, scanning is performed in the order of the third line, fourth line,..., N-th line. The same scan order is applied to the image of each frame.

  Subsequently, the comparison result is input from the comparison circuit 12 and the count value is input from the count circuit 13 to the storage circuit 14. The storage circuit 14 stores the comparison result in association with the count value output from the count circuit 13. By storing the comparison result using the count value as an address, the count value and the comparison result can be associated with each other. However, the correspondence of the present invention is not limited to this.

  Finally, the comparison result associated with the count value output from the storage circuit 14 is input to the detection circuit 16. When the pixel whose signal level difference between the two pixels is equal to or less than the first reference value continues for the second reference value held in the register 15, the detection circuit 16 detects the position information of the first pixel. And the number of consecutive is calculated. The continuous number can be obtained from the number of pixels whose signal level difference between the two pixels is equal to or less than the first reference value based on the count value and the comparison result. Further, the detection circuit 16 detects an effective area and an invalid area based on the position information and the number of consecutive pixels of the first pixel. As described above, since comparison between pixels is performed in the scan order, an invalid area can be detected if the position information and the number of consecutive pixels of the first pixel are known. In addition, an area other than the invalid area can be determined as the valid area.

  Next, taking the case of the screen shown in FIG. 2 as an example, the operation of the image region detection circuit 10 will be described.

  FIG. 2 is a conceptual diagram showing an effective area and an invalid area of an image displayed on the display. This figure conceptually shows a state in which an image having a display aspect ratio different from that of a normal television program, such as a movie, is displayed on a television screen. That is, there are strip-shaped black display areas (invalid areas) extending left and right at the top and bottom of the screen, and there are strip-shaped movie display areas (valid areas) extending in the left and right at the center of the screen.

  Signals of pixels constituting the first frame image are input to the comparison circuit 12 and the count circuit 13 in the scan order. The comparison circuit 12 sequentially compares the signal levels between two consecutive pixels in the scan order for all the pixels included in the first frame image, and outputs the comparison result.

  First, the signal level of each pixel included in the black display area at the top of the screen is all black. Accordingly, the signal level does not change from the position of the first pixel a in the black display area at the top of the screen to the position of the last pixel b.

  For this reason, while the signal of the pixel included in the black display area at the top of the screen is input, the comparison circuit 12 gives a comparison result that the difference in signal level between the two pixels is equal to or less than the first reference value. Is output. The storage circuit 14 stores the comparison result in association with the count value from the count circuit 13. The detection circuit 16 calculates the number of pixels between pixels a and b (continuous number) based on the count value and the comparison result. Here, it is assumed that the second reference value is set so that the number of continuous values is equal to or greater than the second reference value. Therefore, in the detection circuit 16, it can be determined that the area from the pixels a to b is an invalid area.

  Subsequently, the signal level of each pixel included in the movie display area in the center of the screen has a predetermined signal level corresponding to the image. Here, the first and second reference values are set so that a pixel in which the difference in signal level between the two pixels is not more than the first reference value does not continue more than the second reference value. To do.

  Therefore, when a pixel signal included in the movie display area is input, the comparison circuit 12 indicates that the difference in signal level between the two pixels is equal to or less than the first reference value according to the state of the image. A comparison result or a comparison result that is larger than the first reference value is output. In the detection circuit 16, the number of continuations is calculated in the same manner. Here, as described above, since the number of continuations is less than the second reference value, it can be determined that this region is an effective region.

  Finally, the operation while the pixel signals included in the black display area at the bottom of the screen are input is the same as in the case of the black display area at the top of the screen. That is, the comparison circuit 12 outputs a comparison result that the difference in signal level between the two pixels is equal to or less than the first reference value. The storage circuit 14 stores the comparison result in association with the count value from the count circuit 13. In addition, the detection circuit 16 calculates the position information of the first pixel c and the number of consecutive pixels based on the count value and the comparison result.

  Thereafter, in the same manner, the same operation as described above is repeatedly performed for the images after the second frame.

  The storage circuit 14 stores the comparison result from the comparison circuit 12 in association with the count value of the count circuit 13 over a plurality of frames of images, and the detection circuit 16 uses the first pixel over the plurality of frames of images. The valid area and the invalid area may be detected based on the position information and the continuous number. For example, if there is no change in signal level in the same area over a plurality of frames, it is determined as an invalid area. Thereby, the detection accuracy of the region can be further improved.

  As described above, the image area detection circuit 10 can automatically detect the effective area and the invalid area in the image. Accordingly, the image area detection circuit 10 is used to change the correction processing content based on the image information extracted from the pixels in the effective area, thereby always performing appropriate correction for any image. Can do. Further, since the information stored in the storage circuit 14 is only a 1-bit signal as a comparison result, there is an advantage that the circuit scale is small as compared with the case where, for example, one frame image is taken into the frame memory and processed. is there.

  Further, the image area detection circuit 10 can appropriately determine the first and second reference values to make a determination that is optimal for a system that uses the image area detection circuit 10 and an input image. .

  For example, in an image recorded on a video tape or the like, the signal level between two pixels may be higher than the first reference value due to noise even in an invalid area. In this case, attribute information (in this case, an image recorded on a video tape) indicating what kind of signal the image is is received, and the first and second reference values are determined based on the attribute information using a switching circuit. By switching appropriately, it is possible to detect the valid area and the invalid area in the image more accurately.

  For example, there may be a band-like invalid area extending vertically on the left and right sides of the screen. In this case, the continuous number in the left-right direction is small, but the continuous number in the vertical direction is large. Also in this case, it is possible to make an appropriate determination by appropriately changing the first and second reference values. In addition, the image area detection circuit of the present invention is not limited to the case where there are strip-like invalid areas on the top, bottom, left and right of the above screen, and any valid area and invalid area in an image are automatically detected. Can be detected.

The present invention is basically as described above.
The image area detection circuit of the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention. It is.

It is the schematic of one Embodiment showing the structure of the image area | region detection circuit of this invention. It is a conceptual diagram showing the effective area | region and invalid area | region of the image displayed on the display.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image area | region detection circuit 11 Register which hold | maintains 1st reference value 12 Comparison circuit 13 Count circuit 14 Memory | storage circuit 15 Register which hold | maintains 2nd reference value 16 Detection circuit

Claims (1)

An image area detection circuit for detecting an effective area in the image for extracting information for performing correction processing according to an image state, and an invalid area in the image from which the information is not extracted,
A count circuit that counts the number of pixels input in the scan order of the image;
The difference in signal level between two pixels that are consecutive in the scan order is sequentially compared with the first reference value to indicate whether the difference in signal level between the two pixels is equal to or less than the first reference value. A comparison circuit for outputting a comparison result;
A storage circuit for storing the comparison result in association with the count value of the count circuit;
When a comparison result associated with the count value is input and a pixel whose difference in signal level between the two pixels is equal to or less than the first reference value continues for a second reference value or more, the first An image region detection circuit comprising: a detection circuit that detects the effective region and the invalid region by calculating position information and the number of consecutive pixels.

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