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Document reference for working with bitmaps in Cocoa?
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Document reference for working with bitmaps in Cocoa?


  • Subject: Document reference for working with bitmaps in Cocoa?
  • From: Rob Ross <email@hidden>
  • Date: Tue, 24 Oct 2006 11:54:42 -0700

Hi all.

I've been working with the NSBitmapImageRep class in order to create bitmaps from Raster/Sample data I am obtaining from an external source.

I'm having problems getting the "alpha channel" to work correctly.

If I exclude alpha, my bitMapData is just an array of bytes (unsigned char*) that contains the pixels samples in RGB format (three bytes per pixel.)

But if I include an alpha byte in ARGB format, my bitmap no longer displays. Actually, it's all white, but when I draw it selected, with a blue background, my image shows up but only the Red colors show.

So clearly, I'm not understanding how I'm supposed to format the bitMapData array when I want to include an alpha channel.

I would appreciate any document references on this subject. I've read the API docs for NSImage, NSImageRep, and NSBitmapImageRep. I also have the Bunny Core Graphics book, but that's a much lower-level API and doesn't cover this topic.

Thanks,


Rob Ross, Lead Software Engineer
E! Networks
email@hidden
---------------------------------------------------
"Beware of he who would deny you access to information, for in his heart he dreams himself your master." -- Commissioner Pravin Lal



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