NSBitmapImageRep

[Mark Tracy]

I noticed while porting my chromatogram viewer from Mac to GNUstep  
that NSBitmapImageRep -representationUsingType:properties: didn't do  
anything. I thought I would try to get it working. This patch is a  
beginning on that. At the moment, it only supports NSTIFFFileType,  
but stubs for PNG, GIF and JPEG now exist. Along the way, I  
implemented a few TODO and FIXME items.

As I have time and energy, I will work on adding the real support for  
the other formats. If one of the original authors, or someone else  
wants to do it, that is OK with me.

System details: Suse Linux 10.1 running on Parallels Virtual Machine  
on MacOSX 10.4.8(intel). Gcc 4.1.0, libc 2.4, gnustep-make-1.13.0,  
gnustep-base-1.13.0, gnustep-gui-0.11.0, gnustep-back-0.11.0,  
libtiff-3.8.2, libart_lgpl_2-2.3.17 with the default art backend.

I have attached the patch file and a test application I used to  
validate the changes (rough piece of work, but not for public  
consumption).

Cheers,
Mark Tracy

ChangeLog

Sun. 29-Oct-2006 Mark Tracy <tracy454 at concentric dot net>

        1. NSBitmapImageRep 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. One  
because ColorSync is Apple's own data format, and one because there  
is no EXIF support in GNUstep, yet. I propose adding GSICCProfileData  
if and when GNUstep supports color management.

	2. LZW compression in TIFF was disabled for lack of a test to  
determine its availability
        Fix: Implemented NSTiffIsCodecConfigured(codec) in tiff.m
	Comment: As of libtiff-3.7.0 there is a function call to determine  
whether or not a compressor is configured at runtime. For  
libtiff-3.6.0 (earlier?) there are macros #defined in tiffconf.h. The  
implementation checks library version at build-time and uses one of  
the two methods. I don't have an installation of version 3.6, so I  
have not been able to test the second method.

        3. -canCompressUsing:  relied on a static list of capabilities
	Fix: In NSBitmapImageRep.m used the new NSTiffIsCodecConfigured 
(codec) to check for available compressor
	Comment: The static list could be wrong, as it was on my  
installation. The default libtiff-3.8.2 no longer supports oldJPEG.  
Also, libtiff depends on libjpeg to provide that compression service.  
The pay-for edition of Suse does include the patented LZW features  
for TIFF and GIF. (Mercifully that patent expired this year.)

	4. +getTIFFCompressionTypes:count: relied on a static list of  
capabilities
		Fix: In NSBitmapImageRep.m used the new NSTiffIsCodecConfigured 
(codec) to check for available compressors. Also changed the private  
methods _localFromCompressionType: and _compressionTypeFromLocal to  
private class methods so that they could be used within other class  
methods. Altered -initFromTIFFImage:number: and - 
TIFFRepresentationUsingCompression:factor: to use the new class methods.
	Comment: Probably a sub-optimal implementation of checking, but it  
works.

        5. -setProperty:toValue: and -valueForProperty: were not implemented
	Fix: in NSBitmapImageRep.m added a new instance variable  
NSMutableDictionary *  _properties and implemented the accessors.  
Patched -initFromTIFFImage:number: to set the properties  
NSImageCompressionMethod and NSImageCompressionFactor.
	Comment: This feature is used to pass options to/from TIFF, PNG, GIF  
and JPEG in Cocoa. This is not clear from the documentation, but that  
is clearly the behavior for PNG, JPEG and GIF. I have not implemented  
the use of properties in PNG, GIF or JPEG; that will have to wait for  
a future patch. (Probably by someone better than myself.) The - 
setCompression:factor and -getCompressionFactor methods seem to be  
independent of the properties in Cocoa. In one case, the Cocoa docs  
said that reading a TIFF would set the compression  property, but the  
framework did not work that way; I implemented the properties for TIFF.

        6. Checked and updated NSBitmapImageFileType in NSBitmapImageRep.h
	Fix: confirmed the enumeration values against Cocoa, and added  
NSJPEG2000FileType = 5
        Comment: JPEG2000 is not implemented, just reserved a spot for it.

        7. -representationUsingType:properties: was not implemented.
	Fix: Partly implemented in NSBitmapImageRep.m with support for  
NSTIFFFileType. Added stubs for _PNGRepresentationWithProperties: to  
NSBitmapimageRep+PNG.h and .m. Added stubs for  
_GIFRepresentationWithProperties: to NSBitmapImageRep+GIF.h and .m.  
Added stubs for _JPEGRepresentationWithPropertie: to NSBitmapImageRep 
+JPEG.h and .m.
	Comment: All the unimplemented formats issue an NSLog() and return  
nil. It is not clear from Cocoa docs, but if you pass nil for the  
properties, it uses the values stored internally by - 
setProperty:toValue:. I suppose there are some reasonable defaults if  
those have not been set. That is the behavior I implemented.

	8. +representationOfImageRepsInArray:UsingType:properties: was not  
implemented
	Fix: Incomplete implementation in NSBitmapImageRep.m by borrowing  
code from the corresponding TIFF method. I have yet to find the  
explanation of how that actually ought to work.

gnustep-gui-0.11.0-bitmap.patch
Description: Binary data

TestApp.tar.gz
Description: GNU Zip compressed data