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Automatic exposure method based on adaptive threshold segmentation and histogram equalization

A technology of histogram equalization and adaptive threshold, applied in the control of exposure, optics, image enhancement, etc., can solve problems such as overexposure and underexposure of the subject, and achieve the effect of enhancing contrast

Inactive Publication Date: 2012-09-26
NORTHWESTERN POLYTECHNICAL UNIV +1
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Problems solved by technology

[0011] In order to solve the technical problems of underexposure or overexposure of the subject and adaptive segmentation of the target image in the prior art, the present invention provides an automatic exposure method based on adaptive threshold segmentation and histogram equalization

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  • Automatic exposure method based on adaptive threshold segmentation and histogram equalization
  • Automatic exposure method based on adaptive threshold segmentation and histogram equalization

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Embodiment Construction

[0031] An automatic exposure method for histogram equalization based on adaptive threshold segmentation, comprising the following steps:

[0032] 1] Collect a frame of image and record the exposure time t of the frame old ;

[0033] 2] Use the Otsu threshold method to obtain the threshold Δ of the frame image;

[0034] 3] Take the pixel whose image brightness is greater than Δ as the target image;

[0035] 4] Calculate the brightness mean value m(Y) of the target image;

[0036] 5] Perform histogram equalization processing on the target image;

[0037] 6) Calculating the gray mean value Yt of the target image after the histogram equalization process;

[0038] 7] According to the principle that the exposure time is proportional to the average brightness of the image, calculate the exposure time t of the next frame new , according to the formula t new =t old *(Y t / m(Y)); 8] if|t new -t old |new =t old , continue to step 1];

[0039] If|t new -t old |>δ, indicatin...

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Abstract

The present invention relates to an automatic exposure method based on adaptive threshold segmentation and histogram equalization. In accordance with a principle of image brightness being proportional to exposure time, when the photographed image is underexposed, a reflection on the image is that a mean value of the brightness is smaller, and the image after being processed by histogram equalization, will cover grayscale level values of the entire grayscale scope, that is, a grayscale mean value of the image after histogram equalization is larger. The grayscale mean value is adjusted according to tnew=told*(Yt / m(Y)), and the calculated tnew is longer than told, therefore, an aim for increasing exposure time upon underexposure is achieved, and vice versa. With the automatic exposure method based on adaptive threshold segmentation and histogram equalization, technical problems in the prior art of underexposure or overexposure of photographed subjects and target image adaptive segmentation are solved, contrast of the image is enhanced, and adaptive segmentation of a target image as well as effective exposure control of a segmented target image can be realized under any temperature circumstances.

Description

technical field [0001] The invention relates to an automatic exposure method based on adaptive threshold segmentation and histogram equalization. Background technique [0002] The exposure method adopted by the camera can be either metered manual exposure or automatic exposure. [0003] Metering manual exposure is an exposure method in which the photographer chooses the aperture factor and shutter speed, and uses the camera's metering system to determine whether the exposure is appropriate. [0004] Automatic exposure is an exposure method in which the camera automatically selects the aperture factor and shutter speed according to the metering results of its own metering system to obtain accurate exposure. Automatic exposure can be divided into aperture priority automatic exposure, shutter priority automatic exposure, program automatic exposure and other forms. [0005] Aperture-priority automatic exposure means that the aperture factor is selected artificially, and the ca...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N5/235G03B7/08G06T5/40G06T7/00
Inventor 闫荣华王虎汶德胜
Owner NORTHWESTERN POLYTECHNICAL UNIV
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