DCT and Image Compression

In the JPEG image compression algorithm, the input image is divided into

8-by-8 or 16-by-16 blocks, and the two-dimensional DCT is computed for each

block. The DCT coefficients are then quantized, coded, and transmitted. The

JPEG receiver (or JPEG file reader) decodes the quantized DCT coefficients,

computes the inverse two-dimensional DCT of each block, and then puts the

blocks back together into a single image. For typical images, many of the

DCT coefficients have values close to zero these coefficients can be discarded

without seriously affecting the quality of the reconstructed image.

The example code below computes the two-dimensional DCT of 8-by-8 blocks

in the input image, discards (sets to zero) all but 10 of the 64 DCT coefficients

in each block, and then reconstructs the image using the two-dimensional

inverse DCT of each block. The transform matrix computation method is used.- 　　DCT and Image Compression

In the JPEG image compression algorithm, the input image is divided into

8-by-8 or 16-by-16 blocks, and the two-dimensional DCT is computed for each

block. The DCT coefficients are then quantized, coded, and transmitted. The

JPEG receiver (or JPEG file reader) decodes the quantized DCT coefficients,

computes the inverse two-dimensional DCT of each block, and then puts the

blocks back together into a single image. For typical images, many of the

DCT coefficients have values close to zero　these coefficients can be discarded

without seriously affecting the quality of the reconstructed image.

The example code below computes the two-dimensional DCT of 8-by-8 blocks

in the input image, discards (sets to zero) all but 10 of the 64 DCT coefficients

in each block, and then reconstructs the image using the two-dimensional

inverse DCT of each block. The transform matrix computation method is used.