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Re: Problem with image scaling with back-art

From: Alexander Malmberg
Subject: Re: Problem with image scaling with back-art
Date: Mon, 22 Sep 2003 13:11:15 +0200

Tima Vaisburd wrote:
> Here is the code (rotation part does not contribute to the problem and has
> been removed):
> My first question is whether this approach is semantically correct,
> i.e. is this supposed to work?

It looks ok.

> It seems to work fine with xlib, but with back-art I often get garbage in the
> scale range 0.5 < scale < 1.0 if the image to clip from is large enough.
> For instance, the following call produced garbage for 2272 x 1704 source
> image:
> NSImage * clipped =
>     [image imageFromRect: NSMakeRect(502, 369, 1167, 937) scaledBy: 0.655];
> Do you have any ideas what could it be?

Some calculations in back-art were overflowing when the image was too
large. I've added some code to detect this and scale the numbers down a
bit when this is a risk. This loses a bit of accuracy, but prevents the

The test case works here now, so it should be fixed in cvs.

- Alexander Malmberg

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