Image compressor for generating predicted difference code having fixed bit length and program thereof, image decompressor for decoding the code and program thereof, and electronic camera

摘要

An image compressor of the present invention includes a difference calculating unit and a difference requantizing unit. The difference calculating unit calculates a predicted difference between a pixel value of image data and a predicted value (a calculated value of the pixel value predicted from known data). When a magnitude of the predicted difference exceeds a predefined threshold value, the difference requantizing unit applies the coarse quantization steps to requantize the predicted difference to keep a bit range to predetermined size. In this manner, compressed data, in which a bit length of the predicted difference for one pixel is adjusted to a fixed bit length, is generated.