Mon. 20-Nov-2006 Mark Tracy <tracy454 at concentric dot net>
Many changes related to bitmap images
1. NSBitmapImateRep attribute global strings were not defined
Fix: add definitions to externs.h, and declarations to NSBitmapImageRep.h
Comment: Two strings defined in Cocoa were commented out: NSImageColorSyncData
is proprietary to Apple, and NSImageEXIFData has no support elsewhere in
GNUstep. I propose adding GSImageICCProfileData if and when color management
is added to GNUstep.
2. LZW compression in TIFF was disabled for lack of a test of its availability
Fix: Implement NSTiffIsCodecConfigured(codec) in tiff.m
Comment: As of libtiff-3.7.0, there is a function call in the API to test
availability at runtime. For libtiff-3.6.0 (earlier?) there are macros
#defined in tiffconf.h. The implementation check the library version at
compile time, and uses one of the two methods. I have not tested the
second method for lack of an installation of an old libtiff.
3. -canCompressUsing: relied on a static list of capabilities
Fix: Use the new NSTiffIsCodecConfigured(codec) in NSBitmapImageRep.m
Comment: The static list could be wrong, as it was on my system. Also
eliminate the supports_lzw_compression flag.
4. +getTIFFCompressionTypes:count: relied on a static list of compressors.
Fix: Use the new NSTiffIsCodecConfigured(codec) in NSBitmapImageRep.m
Comment: Compares GNUstep supported compressors against actual availability.
Also change the private instance methods _localFromCompressionType and
_compressionTypeFromLocal to private class methods so that they can be used
in -initWithTIFFImage:number: and -TIFFRepresentationUsingCompression:factor:
and +getTIFFCompressionTypes:count: This is probably a clumsy implementation
but it works.
5. -setProperty:toValue: and -valueForProperty: were not implemented
Fix: Add a new instance variable NSMutableDictionary * _properties to
NSBitmapImageRep.h and implemented accessors in NSBitmapImageRep.m. Patch
-_initFromTIFFImage to set compression type and factor in _properties.
Comment: This feature is used to pass options to and from JPEG, PNG, TIFF, and
GIF in Cocoa, although the docs are kind of vague. In one case the Cocoa docs
said the properties were set when reading a TIFF, but the implementation
didn't; I chose to implement the docs. Cocoa does use properties when
exporting bitmaps, so I implemented that.
6. Checked and updated NSBitmapImageFileType in NSBitmapImageRep.h
Fix: confirmed the enumeration values against Cocoa, and added
NSJPEG2000FileType = 5
Comment: JPEG-2000 is not implemented, just reserved a space for it.
7. -representationUsingType:properties: was not implemented
Fix: Implement export of TIFF, JPEG, GIF and PNG in NSBitmapImage.m
Comment: See the change notes for JPEG, GIF, and PNG for more. BMP and JPEG-2000
are not implemented; they just log a message to that effect. As apparently
Cocoa does it this way, if you pass nil for properties, it falls back to
the internal _properties, and if that is empty, there are some safe defaults.
8. +representationfOfImageRepsInArray:UsingType:properties: was not implemented
Fix: Partially implement in NSBitmapImageRep.m
Comment: I just stole the incomplete code from
+TIFFRepresentationOfImageRepsInArray: since I have yet to find an explanation
of how this really ought to work.
9. JPEG export didn't handle alpha channel, properties or errors.
Fix: Add -_JPEGRepresentationWithProperties:errorMessage: to
NSBitmapImageRep+JPEG.h and greatly rework Nicolas Roard's code in
NSBitmapImageRep+JPEG.m. Patch -_initBitmapFromJPEG:errorMessage to
write properties.
Comment: Major rewrite of Nicolas Roard's JPEG export code.
To do: Support for planar bitmaps and support for colorspaces other than
RGB(A).
10. PNG export not implemented
Fix: Add -_PNGRepresentationWithProperties: to
NSBitmapImageRep+PNG.h and implement NSBitmapImageRep+PNG.m
Comment: No support yet for planar bitmaps. Only supports
NS*WhiteColorSpace and NS*RGBColorSpace. Does support alpha. Support for
reading and writing NSImageGamma is experimental. In keeping with Cocoa,
the property NSImageGamma ranges from 0.0 to 1.0; representing the range
of minimum supported gamma to maximum supported gamma, in this case 1.0
to 2.5. This is in contrast to GNUstep where by convention the property
would range from 0.0 to 255.0.
To do: proper error message support
11. GIF export not implemented
Fix: Add -_GIFRepresentationWithPropterties:errorMessage: to
NSBitmapImageRep+GIF.h and implement in NSBitmapImageRep+GIF.m
Comments: Supports only RGB(A) colorspaces, but ignores alpha. Supports
planar or interleaved bitmaps. Supports properties NSImageRGBColorTable.
12. -_initBitmapFromGIF:errorMessage: did not support transparency
Fix: Don't ignore control blocks in NSBitmapImageRep+GIF.m; check for
transparency.
Comment: If a transparent color is found, it adds an alpha channel to the
bitmap. Also, save the color table in properties.
13. -_initBitmapFromGIF:errorMessage: would show the last image in a
multi-image GIF file
Fix: Break the parsing loop after the first image in NSBitmapImageRep+GIF.m
Comment: Also check for frame duration, and set that property. There is not
yet any support for animated GIF. This will require some additional
infrastructure, and I won't do it unless asked.
git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/gui/trunk@24140 72102866-910b-0410-8b05-ffd578937521
