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Re: Drawing transparent images?
From: |
Björn Giesler |
Subject: |
Re: Drawing transparent images? |
Date: |
Mon, 03 Nov 2003 08:03:59 +0100 |
Hi,
On 2003-11-02 18:46:33 +0100 Alexander Malmberg <alexander@malmberg.org> wrote:
> How do you check what you got in the image?
I'm using the image (perhaps a bit naively) for -[NSView
dragImage:at:offset:...]. I just supposed that since images read from TIFF
files can be dragged with transparency, the same is valid for self-drawn images.
>> [[NSColor clearColor] set];
>> NSRectFill(NSMakeRect(0, 0, size.width, size.height));
> This is a noop. Drawing an invisible rectangle doesn't change the
> contents of the buffer. What you want is probably:
>
> NSRectFillUsingOperation(NSMakeRect(...), NSCompositeClear);
Point taken. This *seems* to work if the backend doesn't handle transparent
dragging of self-drawn images (I get black patches where the transparency
should be). However, filling the rect with clearColor set and NSCompositeCopy
gives me a lightgray rect.
> back-art doesn't do text drawing in buffers with alpha (ie. the alpha
> channel is ignored, which causes problems).
I'm not using back-art, just plain old gnustep-back. However, to reduce
problems, I'll be taking the alpha out for now.
Regards & thanks,
Björn