Le lundi 06 octobre 2014 17:02:51, M Lewis a écrit : > We have a software component where users can view/zoom/pan different map > types. > We use GDAL to read the specific part of the image using RasterIO as raw > bytes and then convert to a bitmap for display. > We are now incorporating viewing NITF files and am a little confused in how > the NITF driver handles YCbCr colour space (which some of the NITFs have). > I have found these little snippets from Frank that I found in another post > from 2005: > > /'....Othewise YCbCr images are automatically converted to RGB internally. > However, even in the (default) case where YCbCr images are converted to RGB > internally I *think* that the NITFDataset will still return the YCbCr band > types. This is a bug, and if you want it fixed please file a bug'/ > > Also in the NITFDataset code there is a comment: > > / /* FIXME? Does it make sense if the JPEG/JPEG2000 driver decodes */ > /* YCbCr data as RGB. We probably don't want to set */ > /* the color interpretation as Y, Cb, Cr *// > > Here is a typical gdalinfo dump of a NITF file that I have to deal with: > > Band 1 Block=640x1 Type=Byte, ColorInterp=YCbCr_Y > Overviews: 320x240, 160x120 > Image Structure Metadata: > COMPRESSION=JPEG > Band 2 Block=640x1 Type=Byte, ColorInterp=YCbCr_Cb > Overviews: 320x240, 160x120 > Image Structure Metadata: > COMPRESSION=JPEG > Band 3 Block=640x1 Type=Byte, ColorInterp=YCbCr_Cr > Overviews: 320x240, 160x120 > Image Structure Metadata: > COMPRESSION=JPEG > > The question is can it be assumed (based on Franks comments) that in the > decoding by the JPEG driver that Band 1 has been converted to Red even > though it states above that the band is YCbCr?
Martin, Yes, Frank's comment is right. The color interpretation is wrong. It should be RGB, since on-the-fly colorspace conversion from YCbCr to RGB has been done. That should be fixed Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
