Extracting Y Cb Cr from jpg file

Extracting Y Cb Cr from jpg file

Post by shlo » Wed, 24 Jul 2002 21:10:24

I'm uisng the IJT c source liberary to decompress jpg images.
I'm tring to extract only the y plan from the JPG file directly
but i do not get any resaults.
The code i'm using is:

struct jpeg_error_mgr jerr;
int row_stride;         /* physical row width in output buffer */
cinfo.err = jpeg_std_error(&jerr);
struct jpeg_source_mgr jsrc;

cinfo.src = &jsrc;
jsrc.init_source = init_source;
jsrc.fill_input_buffer = fill_input_buffer;
jsrc.skip_input_data = skip_input_data;
jsrc.resync_to_restart = jpeg_resync_to_restart; /* use default method */
jsrc.term_source = term_source;
jsrc.bytes_in_buffer = length;
jsrc.next_input_byte = (JOCTET *) bufferIn;
cinfo.out_color_space = JCS_YCbCr;

1. Does any one has a sample code that allow the extraction of the Y plane
2. Does any one has a samlpe code of how to use the "sequential jpeg"
   to extarct th Y Cb Cr in 2 steps

Best regards


1. MPEG 1 : Cr and Cb block

In I-frame, each intra-macroblock can  be further decomposed into 4
illuminance blocks, 1 Cr and Cb. The 2 chrominance blocks convey color
information, how should I make use the Cr and Cb as well as the
illuminance blocks in order to restore a color frame. Can you kindly
brief me the steps? ( I've successfully decoded the I-frame/illuminance
4 blocks,up to here only).

Please email me.
Great thanks!

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