There are provided an image compression device, method, and program, a compression code data encoding device, method, and program, and a decoding device, method, and program. The image compression device includes: means for dividing the entire image into blocks, calculating an inclined plane or an outer edge inclined plane for calculating a parameter specifying the inclined plane or the outer edge inclined plane for approximating the respective blocks from the block pixel values, calculating an error amount or a difference value to calculate a difference between the inclined plane or the outer edge inclined plane and the respective pixel values, and calculating an encoding correction amount of each block; and encoding portion for reversibly encoding the parameter specifying the inclined plane or the outer edge inclined plane. The encoding device includes synthesis portion for judging a change amount of generation probability contained in the data to be compressed and obtained in time series, generating difference probability data including a generation probability of data having a large generation probability, and synthesizing the generated difference probability data with the compression/encoding data.