JPEG ENCODER

PROGRAM CONSTRUCTS A JPEG FILE FROM THE INPUT BMP,TIFF FILE FORMATS.

1.subsampling
2.level shifting --> dct -->quantization
3.DPCM OF DC COEFFICIENTS+HUFFMAN ENCODING.
4.ZIGZAG SCAN OF AC COEFFICIENTS
5.RUNLENGTH ENCODING + HUFFMAN ENCODING OF AC COEFFICIENTS.
6.ARRANGING THE AC DC COEFFICIENTS OF LUMA ,CB , CR ACCORDING TO JPEG STANDARD. (420 SUBSAMPLING) , REFER TO FIG 'itut81.JPG'.
7.COMBINING (LUMA,CB,CR) BITSREAMS OF 3 COMPONENTS.
7.BYTE STUFFING
8.TAKING 1 BYTE(8 BITS OF CODED STREAM) AND CONVERTING INTO DECIMAL EQUIVALENT.
9.WRITING JFIF HEADER FORMAT .
10. WRITING THE ENCODED BITSTREAM INTO THE ENTROPY CODED SEGMENT OF JFIF HEADER.

11.DECODING PART IS DONE BY THE IMAGE VIEWER ( DEFAULT IMAGE VIEWER LIKE MICROSOFT PICTURE , FAX VIEWER,PICASA, OR ANY OTHER VIWEWRS)

NOTE : I HAVE REPEATED THE DC ENTROPY AND AC ENTROPY CODING PROCEDURE , SEPERATELY FOR EACH COMPONENTS (LUMA,CB,CR). IT CAN BE AVOIDED BY WRITING A SINGLE FUNCTION EACH FOR AC AND DC ENTROPY ENCODING.

functions 'table_huff 'is same as 'table_bitcodval' .

THANKS