Patent ID: 7751616

Claim:
A coding apparatus comprising: a memory; and a controller including: a color space conversion unit that converts input image data into image data which is represented in another color space, the input image data including a gradation value, the converted input image data being composed of a luminance or lightness component and other color components; a gradation changing unit that changes the gradation value of the input image data, based on the converted image data; and a predictive coding unit that performs predictive coding on the image data subjected to the gradation value change, wherein the gradation changing unit determines whether to change the gradation value of the input image data, based on the image data converted by the color space conversion unit, and the gradation changing unit calculates a difference between a pixel value of a pixel of the converted image data and a predicted pixel value of the pixel of the converted image data for each color component, and compares the difference with a tolerance set for each color component to determine whether to change the gradation value of the input image data.