Actually, that occurred under 10.5 as well - what happens is that some
operations, it would seem those involving Core Image, cause the
internal representation to go to RGBA. Which is fine, but there
doesn't seem to be a way to write a plain RGB format TIFF. I had to
incorporate a third-party TIFF module to do that, as RGBA TIFF files
aren't very compatible with anything other than Apple.
Sandy
On Oct 12, 2009, at 5:07 PM, Ken Ferry wrote:
On Mon, Oct 12, 2009 at 4:36 AM, Peter C <[email protected]>
wrote:
I just stumble into a feature (or a bug ?), NSImage
TIFFRepresentation
produce RGB TIFF with a layer (when open under Photoshop).
Previously it
produce plain RGB TIFF under OS 10.5 and below. This cause some
part of my
programs interpret wrong RGB data, expecting 3 bytes instead of 4
bytes for
a RGB pixel. There is no mention in the documents about this
"feature".
Is there a way to restore the previous behavior of
TIFFRepresentation ?
You can look at CGImageDestination to get more options, but I don't
think
there's anything that provides control at that level.
In many cases there _must_ be data munging between the in memory pixel
format and the on-disk file format. The precise munging is not
defined on
either input or output.
That is, don't make pixel format assumptions. The AppKit release
notes<http://developer.apple.com/mac/library/releasenotes/Cocoa/AppKit.html
>discuss
how to avoid making pixel format assumptions in the section
"NSBitmapImageRep: CoreGraphics impedence matching and performance
notes".
-Ken
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