JPEG compression is composed of three compression techniques applied in successive layers, including chrominance subsampling, discrete cosine transformation and quantization, and run-length Delta &Huffman encoding. Chroma subsampling involves implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance. A discrete cosine transform expresses a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequencies.