remove alpha channel from bitmap
remove alpha channel from bitmap
- Subject: remove alpha channel from bitmap
- From: Jason Alexander <email@hidden>
- Date: Wed, 30 Apr 2003 12:20:25 +0100
If I have an instance of NSImage, anImage, initialized from a PDF file,
I know I can save that to a bitmap file in TIFF format via
[[anImage TIFFRepresentation] writeToFile: @"/tmp/foo.tiff"
atomically: YES];
To get the bitmap in PNG format, I tried the following variant:
NSData *tiffData = [anImage TIFFRepresentation];
NSBitmapImageRep *bitmap = [NSBitmapImageRep
imageRepWith
Data:tiffData];
[[bitmap representationUsingType:NSPNGFileType properties:nil]
writeToFile: @"/tmp/foo.png" atomically: YES];
However, although Preview.app displays foo.png correctly, other apps
(like GraphicConverter) don't -- all I see in GC is a black square, and
an inverse of the bitmap if I choose "Show Alpha Channel."
How can I strip the alpha channel from the TIFF representation to get a
"pure" PNG file (or JPEG, or BMP,...) that doesn't contain an alpha
channel, so that other apps can import the bitmap?
Thanks,
Jason
--
J. McKenzie Alexander
Department of Philosophy, Logic and Scientific Method
London School of Economics and Political Science
Houghton Street, London WC2A 2AE
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