An image-processing apparatus to compress digital image data, includes a memory that stores a digital image in a first storage space. The image-processing apparatus further includes one or more image-processing circuits that selects a block from a plurality of blocks of the digital image. A plurality of encoded blocks is generated by application of a plurality of sequential encoding schemes on the selected block. One encoded block is detected from the generated plurality of encoded blocks that has a maximum bit-coverage value. A sequential encoding scheme is selected from the plurality of sequential encoding schemes as an optimal sequential encoding scheme. The selected sequential encoding scheme is associated with the detected encoded block with the maximum bit-coverage value. The selected block of the digital image is converted to a compressed bit stream storable in a reduced second storage space in the memory, by use of the sequential encoding scheme.