Re: remove alpha channel from bitmap
Re: remove alpha channel from bitmap
- Subject: Re: remove alpha channel from bitmap
- From: email@hidden
- Date: Wed, 30 Apr 2003 19:35:02 +0200
On mercredi, avril 30, 2003, at 01:20 PM, Jason Alexander wrote:
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
imageRepWithData: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?
Maybe it's easier to just use QuickTime and its import/export features.
There must be at least one sample code on this topic on the ADC site.
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