To provide an image compression unit and an image file which will not reduce the micro-components of image and improves the compression efficiency, even with complicated images.

The image compressor 100 comprises an image filter 150. The filter comprises a means 102 for measuring a histogram in units of context after scanning an input image, a context remap means 103 for making a context remap database for replacing the original contexts, taking the same pixel value with contexts having close distances with the original contexts and high frequency of appearance using the histogram, and a filter means 104 for converting the pixel values of the image read from an input picture memory, using the context remap database.