NSBitMapImageRep gives error when copying existing image

[OS X 10.5.6. Xcode 3. All updates. No funny stuff.]

I'm getting the following error in my log

<Error>: CGBitmapContextCreate: unsupported parameter combination: 8
integer bits/component; 24 bits/pixel; 3-component colorspace;
kCGImageAlphaNone; 1536 bytes/row.

when I execute the last line of the following:

NSBitmapImageRep* showListRep = nil;
showListRep = [[[[leftImageView image] representations] objectAtIndex:0]
copy];

[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:[NSGraphicsContext
graphicsContextWithBitmapImageRep:showListRep]];


The 'leftImageView' in question is an NSView which has had an image
dragged into it from the Finder. I have tried it with two images
(generated by other people and working perfectly in all other situations)
and both give similar messages. In each case the maths makes sense.

I also tried making up my own image using 'initWithBitmapDataPlanes' and
got the same error when I used the same parameters. However, if I set it
to use 4 samples per pixel (even though I don't need Alpha for this) the
error went away.

If I understand this correctly, the complaint is that it can't use a 3-
component representation as a graphics context. If that's the case, how
come my programs can use these images for other image operations without
problems ?

My finished program doesn't need to work with and OS X < 10.4.

Simon.
--
http://www.hearsay.demon.co.uk

In article <1P%4l.78083$Xy3.43162@newsfe01.ams2>,
Simon Slavin <slavins.delete.these.four.words DeleteThis @hearsay.demon.co.uk>
wrote:

> [OS X 10.5.6. Xcode 3. All updates. No funny stuff.]
>
> I'm getting the following error in my log
>
> <Error>: CGBitmapContextCreate: unsupported parameter combination: 8
> integer bits/component; 24 bits/pixel; 3-component colorspace;
> kCGImageAlphaNone; 1536 bytes/row.


Only certain parameter combinations are supported.

<http://developer.apple.com/documentation/GraphicsImaging/Conceptual/draw
ingwithquartz2d/dq_context/chapter_3_section_4.html#//apple_ref/doc/uid/T
P30001066-CH203-BCIBHHBB>

> If I understand this correctly, the complaint is that it can't use a 3-
> component representation as a graphics context. If that's the case, how
> come my programs can use these images for other image operations without
> problems ?

Because those other operations aren't trying to create bitmap graphics
context from the same images along the way.

--
"Harry?" Ron's voice was a mere whisper. "Do you smell something ... burning?"
- Harry Potter and the Odor of the Phoenix