An image compression method is used for processing a plurality of pixels of an image. The image compression method includes the steps of receiving N pixels; analyzing the N pixels and generating a content type corresponding to the N pixels; obtaining a quantization parameter and a coding parameter corresponding to the N pixels according to the content type and a currently available buffer space value; obtaining N quantized differences corresponding to the N pixels through a prediction and quantization way according to values of the N pixels and the quantization parameter; and encoding the N quantized differences according to the N quantized differences and the coding parameter.