Image file processing method

An image file processing method, comprising:

• obtaining an image file of an image, wherein the image is divided into a plurality of image blocks, at least one of the image blocks is regarded as a minimum coded unit (MCU), one row or multiple rows of the MCUs sequentially defines the image into a plurality of bands, wherein the image file comprises:
• a bit stream, indicating a compression data of the image and having a plurality of clips respectively corresponding to the bands, wherein each clip has a plurality of sub-clips, and in each clip, the sub-clips respectively correspond to the MCUs of the bands corresponding to the clips;
• and
• an Exchangeable Image File (EXIF) data, comprising:
• a plurality of band indicators, respectively corresponding to the bands, and each indicating a position of the clip corresponding to the band in the bit stream;
• a plurality of MCU indicators, respectively corresponding to the MCUs, and each indicating a position of the sub-clip corresponding to the MCU in the clip;
• and
• a plurality of hybrid direct current (DC) coefficients, sequentially corresponding to an image DC coefficient of each sub-clip;
• reading at least one of the band indicators and the MCU indicator according to an expanded range for selecting part of the image;
• obtaining a referential DC coefficient according to the hybrid DC coefficient corresponding to the first MCU covered by the expanded range;
• and
• decoding at least one sub-clip corresponding to at least one MCU covered by the expanded range in the bit stream according to the read band indicator, the MCU indicator and the referential DC coefficient, so as to obtain at least one of the MCU.