Image processing apparatus having means for controlling exposure using an orthogonal transformation coefficient

Claim 1

An image processing apparatus comprising: an image pickup unit arranged to photograph an image and convert the image into an image signal in units of pixels; a transformation unit arranged to segment the image signal to form blocks each including a plurality of pixels, perform an orthogonal transformation on the image signal in the units of blocks, and obtain transformation coefficients; an encoding unit arranged to encode the transformation coefficients obtained by said transformation unit in units of the blocks and output encoded image data; an extracting unit arranged to extract, as specific blocks, a part of the blocks formed by said transformation unit; and a controlling unit arranged to control an exposure of said image pickup unit based upon DC components of the transformation coefficients of the specific blocks extracted by said extracting unit, wherein said controlling unit integrates DC components from the specific blocks and controls the exposure in a first control width when an integrated result of the DC components is not within a range of a first level, controls the exposure in a second control width narrower than the first control width when an integrated result of the DC components is within the range of the first level but not within a range of a second level narrower than the range of the first level, and completes control of the exposure when an integrated result of the DC components is within the range of the second level.