Automatic exposure method based on objective area in image

Abstract

The present invention discloses an automatic exposure method basing on the target area in the image. The method comprises the following procedures: (a) executing target detecting to the image of the currently detected frame to judge whether a target exists; (b) confirming the brightness value of the currently detected frame used for calculating the exposure parameter according to the brightness value of the target area in the currently detected frame and the brightness value of the target area in the previous detected frame when a target exists; and (c) calculating the exposure parameter according to the brightness value of the currently detected frame and executing automatic exposure adjusting to the subsequent image until the brightness of the last detected frame is confirmed and the exposure parameter is calculated. The method adopting the invention can facilitate that the target area in the image has appropriate brightness information relative to the total graph background. The signal-to-noise ratio of the target area is increase. The insufficient brightness or over exposure in the target area can be prevented. The effect is especially evident in the target backlight or bright light condition.

Description

technical field [0001] The invention relates to an automatic exposure method in a digital camera device, in particular to an automatic exposure method according to a target area (interesting area) in an image. Background technique [0002] In the prior art, the automatic exposure method in the digital camera equipment performs automatic exposure adjustment by calculating the brightness value of the whole image, without taking into account the brightness of some important areas in the image, that is, the target area (such as the face area or the license plate area), so that After exposure, the target area in the image cannot achieve a good display effect. [0003] For example, in the image used for video surveillance or video conferencing, the face area is the target area in the image, which has higher display effect requirements. When the face is backlit or the face is illuminated by strong light, the existing full-image The method of exposure setting makes the brightness o...

AI Technical Summary

Problems solved by technology

Due to the difference in ambient light, the existing exposure settings for the whole image sometimes cannot obtain a license plate image with appropriate brightness. For example, at night, due to the influence of the environment and its own car lights, the brightness of the license plate area may be insufficient; The illumination of the vehicle's headlights makes the license plate area overexposed

Insufficient brightness or overexposure of the license plate area will lose a lot of useful information, which will bring difficulties to subsequent license plate recognition and vehicle management

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