An image encoding method is for obtaining, from a pixel data string containing pixel values of a plurality of pixels in a pixel array where the pixels are arrayed, a pixel data string containing a quantized representative value into which at least one of the pixel values is encoded. Encoding is performed by allocating a specific quantized representative value when a pixel value of a pixel is a specific pixel value, and by allocating a quantized representative value other than the specific quantized representative value when the pixel value is other than the specific pixel value.