Re: [artworks] Zooming changes image colour
- From: Martin Wuerthner <lists@xxxxxxxxxxxxxxx>
- To: artworks@xxxxxxxxxxxxx
- Date: Mon, 28 Sep 2009 15:43:26 +0200
In message <685f04a150.zen44412@xxxxxxxxx>
Simon Smith <simon_smith@xxxxxxxxx> wrote:
> The linked image demonstrates a colour change associated with high levels of
> zoom. At a zoom level of 3788% or less, the colours appear correct. At 3789%
> or higher, the colours go wrong. I have no idea why 3789% is the magic
> number. I'm on AW2.93. I also run at 1280x1024x16Mx75Hz using Geminus 1.32.
> just in case the Geminus settings matter, Geminus has Sprite cacheing turned
> on for ArtWorks, Sprite acceleration and Window contents caching off. DMA
> acceleration is on, as is JPEG decoding and plotting. I believe those are
> the Geminus/ArtWorks settings I'm supposed to have.
> http://simon-smith.org/images/chinese_mat.art
Yes, I see. This is a coordinate range problem with radial fills at
very high zoom levels. It happens because the radial fill end points
in zoomed coordinate space exceed the 32 bit number range. In practice
that means that you can only see a radial fill across a complete A4
page correctly up to about 3700% zooming. In most cases, the end
points are closer to each other in which case they work up to maximum
zoom (4000%). With even larger page sizes the problem can be noticed
earlier. I suppose this could be a problem if someone wanted to
produce a very high resolution bitmap of a large drawing. Since this
is a fundamental issue it is unlikely that it can be fixed easily.
With linear fills, there is a similar problem, but instead of
incorrect rendering you get an "Overflow while transforming point"
error, which is the usual indicator for a coordinate range problem.
Martin
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