Hi Even, Thanks for the info, but I need it other way round - RGB to CMYK conversion. As Frank said, it's possible to create a CMYK result using gdal_translate giving it an extra band as a parameter (i.e. -b 1 -b 2 -b 3 -b 1), but the end result is of no use since that extra band (along with R, G and B) takes some color mangling I'm not very familiar with. And there's not much to read about it, here's what I found (citations ahead):
http://semmix.pl/color/extrans/etr10.htm Transformation RGB, CMY, CMYK Formal transformation of the components RGB into the components CMY or inversely is as follows: we have color RGB=(r,g,b) then color CMY=(1-r,1-g,1-b) we have color CMY=(c,m,y) then color RGB=(1-c,1-m,1-y). Transformation of CMY into CMYK is presented as algorithm: k=min(c,m,y), CMYK=(c-k,m-k,y-k,k) This explanation seems sane enough, but then: "we have color RGB=(r,g,b) then color CMY=(1-r,1-g,1-b)" is giving me a headache with "1-r" etc. part. What do they mean by "1-r"? :-) Furthermore, RGB to CMYK is supported by .NET 3.5 only, and giving it a shot via GDAL managed wrappers is also viable solution (thanks Tamas for LoadBitmapDirect and SaveBitmapDirect C# examples). I'm working with .NET 2.0 and can't use this approach, but here's the code anyways (author unknown): using System; using System.IO; using System.Windows.Forms; using System.Windows.Media; using System.Windows.Media.Imaging; ... Stream imageStream = new FileStream(@"C:\temp\mike4.jpg", FileMode.Open, FileAccess.Read, FileShare.Read); BitmapSource myBitmapSource = BitmapFrame.Create(imageStream); FormatConvertedBitmap newFormatedBitmapSource = new FormatConvertedBitmap(); newFormatedBitmapSource.BeginInit(); newFormatedBitmapSource.Source = myBitmapSource; newFormatedBitmapSource.DestinationFormat = PixelFormats.Cmyk32; newFormatedBitmapSource.EndInit(); BitmapEncoder encoder = new TiffBitmapEncoder(); encoder.Frames.Add(BitmapFrame.Create(newFormatedBitmapSource)); Stream cmykStream = new FileStream(@"C:\temp\mike4_CMYK.tif", FileMode.Create, FileAccess.Write, FileShare.Write); encoder.Save(cmykStream); cmykStream.Close(); Again, it would be great if someone could explain how to do it via GDAL wrappers running on .NET 2.0 (I'm using GDAL build from FWTools). Regards, Maksim Sestic -----Original Message----- From: Even Rouault [mailto:[EMAIL PROTECTED] Sent: Thursday, August 21, 2008 20:44 To: [email protected] Cc: Maksim Sestic Subject: Re: [Gdal-dev] GTiff / gdal_translate / CMYK - problem Maksim, I've just done a few changes in the GeoTIFF driver to enable basic CMYK support. See the log message of http://trac.osgeo.org/gdal/changeset/15178. And for examples : http://trac.osgeo.org/gdal/changeset/15179. Regards, Even Le Wednesday 20 August 2008 11:46:06 Maksim Sestic, vous avez écrit : > Hi all, > > I'm having troubles with gdal_translate while creating uncompressed > 3-band GTiff with CMYK photometric representation. Well, at least CMYK > representation recognized by Photoshop, which is > PhotometricInterpretation=5. If I use recommended gdal_translate -co > 'PHOTOMETRIC=CMYK' switch I keep getting "grayscale" (!) result, > again, that's what Photoshop says (PhotometricInterpretation=1). > > What other -co parameters should I set to make it work? I'm using > gdal_translate from FWTools 2.2.3 > > > Here's the gdalinfo reports: > > 1) For RGB raster parsed with gdal_translate -co 'PHOTOMETRIC=CMYK' > switch: > > Size is 945, 945 > Coordinate System is `' > Metadata: > AREA_OR_POINT=Area > TIFFTAG_SOFTWARE=MyApp > TIFFTAG_DATETIME=20.08.2008 02:51:37 > TIFFTAG_XRESOLUTION=240 > TIFFTAG_YRESOLUTION=240 > TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch) Image Structure Metadata: > INTERLEAVE=PIXEL > Corner Coordinates: > Upper Left ( 0.0, 0.0) > Lower Left ( 0.0, 945.0) > Upper Right ( 945.0, 0.0) > Lower Right ( 945.0, 945.0) > Center ( 472.5, 472.5) > Band 1 Block=945x2 Type=Byte, ColorInterp=Gray Band 2 Block=945x2 > Type=Byte, ColorInterp=Undefined Band 3 Block=945x2 Type=Byte, > ColorInterp=Undefined > > Side note: I also tried using -co 'PHOTOMETRIC=YCBCR' and > 'PHOTOMETRIC=CIELAB'switches but then gdal_translate crashes. > > > 2) Photoshopped tiff with CMYK mode set (that's what I need to get): > > Driver: GTiff/GeoTIFF > Files: 080417_75008_000000017_CMYK.tif Size is 945, 945 Coordinate > System is `' > Metadata: > TIFFTAG_SOFTWARE=Adobe Photoshop CS3 Windows > TIFFTAG_DATETIME=2008:08:20 02:21:08 > TIFFTAG_XRESOLUTION=240 > TIFFTAG_YRESOLUTION=240 > TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch) Image Structure Metadata: > INTERLEAVE=PIXEL > Corner Coordinates: > Upper Left ( 0.0, 0.0) > Lower Left ( 0.0, 945.0) > Upper Right ( 945.0, 0.0) > Lower Right ( 945.0, 945.0) > Center ( 472.5, 472.5) > Band 1 Block=945x2 Type=Byte, ColorInterp=Undefined Band 2 Block=945x2 > Type=Byte, ColorInterp=Undefined Band 3 Block=945x2 Type=Byte, > ColorInterp=Undefined Band 4 Block=945x2 Type=Byte, > ColorInterp=Undefined > > Also, there's another Photoshop's TIFF tag, "NativeDigest", which I >don't really get (it's not recognized by gdalinfo) - here's the xmp output: > <tiff:NativeDigest > >xmlns:tiff="http://ns.adobe.com/tiff/1.0/";>256,257,258,259,262,274,277, >284, >530,531,282,283,296,301,318,319,529,532,306,270,271,272,305,315,33432;4 >6BB97 3B26CC7DED3A1C59F8F9AC7EC5</tiff:NativeDigest> > > > Regards, > Maksim Sestic __________ Information from ESET NOD32 Antivirus, version of virus signature database 2888 (20080220) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 2888 (20080220) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
