Partial expansion method of encoded images and image processing apparatus

An image processing apparatus comprising:

• a means for storing, in a storage device, an encoded image having been encoded on a macroblock basis;
• a cache file creation means for creating map data from bitstream of the encoded image, the map data being utilized to decode at least one of macroblock of the encoded image, creating a shrunken image of a predetermined size based on a screen resolution of a display device, and storing the map data and the shrunken image so as to relate the map data and the shrunken image with the encoded image in the storage device;
• a shrunken image output means for outputting, to the display device, the shrunken image related with the encoded image to be displayed based on a control request received from an input device,
• a used block determination means for determining at least one macroblock to be decoded based on a display area of the shrunken image;
• a partial decoding means for partially decoding the encoded image for the determined macroblock using the map data;
• and
• a partially decoded image output means for outputting to the display device, the image data of the display area of the partially decoded image created by the partial decoding means.