[pygame] pygame.scrap bitmap stuff

[Bob Ippolito <bob@xxxxxxxxxx>]

I went ahead and implemented (read: prototyped) scrap bitmap support  
for Mac OS X, but the implementation is terribly inefficient. Pygame  
surfaces aren't terribly accessible from Python outside of surfarray  
(which I didn't want to depend on).

Going from a Surface to the pasteboard is particularly painful in  
this implementation:

1. Surface to PNG (on disk!)
2. NSImage from on-disk PNG
3. NSImage to TIFF
4. TIFF to pasteboard

The absolute fastest route (which doesn't exist in pygame) would be:

1. Surface to TIFF (in memory)
2. TIFF to pasteboard

pygame doesn't have any TIFF writing capability at all, a compromise  
here would to at least avoid hitting the disk and zlib:

1. Surface to BMP (in memory)
2. BMP to NSImage
3. NSImage to TIFF
4. TIFF to pasteboard

Unfortunately this also isn't currently possible because pygame  
doesn't support BMP writing anymore (or so it seems from a quick look  
at the code) and it definitely won't do it to memory instead of disk.  
Cocoa does not support TGA.

Going the other way is also gnarly, but mostly because I didn't want  
to think more than I had to:

1. pasteboard to NSImage
2. NSImage to TIFF
3. TIFF to NSBitmapImageRep
4. NSBitmapImageRep to BMP (in memory)
5. Surface from BMP

Getting a NSBitmapImageRep directly from the NSImage (steps 2+3  
combined) is definitely possible without going between TIFF, but I  
was too lazy to think about what that would do for vector graphics  
(e.g. PDF on the pasteboard) and screen representations. It's not  
necessarily true that NSImage will have a NSBitmapImageRep cached  
already.

Going from NSBitmapImageRep to a Surface without hitting BMP is  
possible, but there's a bunch of formats the NSBitmapImageRep could  
be in and I didn't want to think about that either :)

In any case, pygame.scrap is 100% implemented on Mac OS X, and it's  
kinda fun to play with. An easy way to test is to take a partial  
screen cap to the pasteboard (shift-ctrl-cmd-4) and blit it in your  
pygame app. You should be able to bring in anything from the  
pasteboard that NSImage can load: icons, jpeg, png, pdf (!), tiff, etc.

-bob