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2006.03.29 22:22 "TIFF_UPSAMPLED", by Frank Warmerdam

2006.03.30 18:44 "Re: TIFF_UPSAMPLED", by Antonio Scuri

2006.03.30 18:44 "Re: TIFF_UPSAMPLED", by Antonio Scuri

Hi,

I solved my problem when saving/loading YCbCr color mode JPEG 
compressed TIFF in a different way.

When encoding I do not want to provide a downsampled output so I changed:
function JPEGPreEncode, at line 1298 in tif_jpeg.c from CVS
FROM
                 if (sp->photometric == PHOTOMETRIC_YCBCR) {
                         if (sp->jpegcolormode == JPEGCOLORMODE_RGB) {
                                 sp->cinfo.c.in_color_space = JCS_RGB;
                         } else {
                                 sp->cinfo.c.in_color_space = JCS_YCbCr;
                                 if (sp->h_sampling != 1 || 
                                     sp->v_sampling != 1)
                                         downsampled_input = TRUE;

TO
                 if (sp->photometric == PHOTOMETRIC_YCBCR) {
                         if (sp->jpegcolormode == JPEGCOLORMODE_RGB) {
                                 sp->cinfo.c.in_color_space = JCS_RGB;
                         } else {
                                 sp->cinfo.c.in_color_space = JCS_YCbCr;
                                 tif->tif_flags |= TIFF_UPSAMPLED; /* 
Changed for IM
                                 if (sp->h_sampling != 1 || 
                                     sp->v_sampling != 1)
                                         downsampled_input = TRUE;   */

And

Also when decoding I do not want to get a downsampled output so I changed:
function JPEGPreDecode, at line 801 in tif_jpeg.c from CVS
FROM
         if (td->td_planarconfig == PLANARCONFIG_CONTIG &&
             sp->photometric == PHOTOMETRIC_YCBCR &&
             sp->jpegcolormode == JPEGCOLORMODE_RGB) {
         /* Convert YCbCr to RGB */
                 sp->cinfo.d.jpeg_color_space = JCS_YCbCr;
                 sp->cinfo.d.out_color_space = JCS_RGB;
         } else {
                         /* Suppress colorspace handling */
                 sp->cinfo.d.jpeg_color_space = JCS_UNKNOWN;
                 sp->cinfo.d.out_color_space = JCS_UNKNOWN;
                 if (td->td_planarconfig == PLANARCONFIG_CONTIG &&
                     (sp->h_sampling != 1 || sp->v_sampling != 1))
                         downsampled_output = TRUE;
                 /* XXX what about up-sampling? */

TO
         if (td->td_planarconfig == PLANARCONFIG_CONTIG &&
             sp->photometric == PHOTOMETRIC_YCBCR &&
             sp->jpegcolormode == JPEGCOLORMODE_RGB) {
         /* Convert YCbCr to RGB */
                 sp->cinfo.d.jpeg_color_space = JCS_YCbCr;
                 sp->cinfo.d.out_color_space = JCS_RGB;
         } else {
                         /* Suppress colorspace handling */
                 sp->cinfo.d.jpeg_color_space = JCS_UNKNOWN;
                 sp->cinfo.d.out_color_space = JCS_UNKNOWN;
                 tif->tif_flags |= TIFF_UPSAMPLED;  /* Changed for IM
                 if (td->td_planarconfig == PLANARCONFIG_CONTIG &&
                     (sp->h_sampling != 1 || sp->v_sampling != 1))
                         downsampled_output = TRUE;   */
                 /* XXX what about up-sampling? */
         }

  Hope this helps too.

Best,
scuri