An apparatus for compressing an image data with an array of pixels comprising a data length is disclosed. The apparatus comprises a rearranging unit, a transformation operator, a quantizer and a coding operator. The rearranging unit is configured to transform the array to form a rearranged block with a mark value. The transformation operator is configured to obtain transform coefficients of the rearranged block according to a predetermined transformation. The quantizer is configured to quantize the transform coefficients. The coding operator is configured to generate a result data by coding the transform coefficients which is quantized and the mark value according to a predetermined coding method.