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nitrospectide

GIF export, white bkgrd goes off-white

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This file is set up with the map in front of a solid 255/255/255 white rectangle as the background. When I export it as a 256 color GIF, the background goes off-white, and parts of it dither. Why, and how do I stop that?

post-54273-0-45406400-1494000341_thumb.gif

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Actually, I don’t know why it doesn’t work, but here is a workaround:

  • Export it as a PNG file
  • Open this file in Preview.app
  • Export from Preview.app as a GIF file. In order to do so, select File > Export … in Preview, in the following dialog hold down the Alt (Option) key while clicking the Export Options menu, select GIF.

Hope that helps …  :)

Alex

post-1198-0-29658700-1494520277_thumb.gif

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Actually, I don’t know why it doesn’t work, but here is a workaround:

  • Export it as a PNG file
  • Open this file in Preview.app
  • Export from Preview.app as a GIF file. In order to do so, select File > Export … in Preview, in the following dialog hold down the Alt (Option) key while clicking the Export Options menu, select GIF.

Hope that helps …  :)

Alex

I appreciate the help - though I'm puzzled as to why anyone should have to do this.

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Sure, it shouldn’t be like that. I haven’t used GIF images for a long time, but unless I am mistaken, a palette table of a GIF file can hold up to 256 values drawn from an RGB/8 color space. So if your drawing would need more than 256 different color values to be rendered perfectly, the export algorithm will have to decide what color values to put in the table and how to render your document in the best possible way on the basis of these values. So dithering is some sort of compromise.

 

In any case, I fear the GIF export algorithm is somewhat unfinished at the moment. Preview does it apparently better. And whenever I select a “Custom” palette in Affinity Photo, I will get an error (see below). Hmm …  :unsure:

post-1198-0-14622100-1494532908_thumb.png

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@MEB Hi. The issue still exists in Photo for Windows. I need to save dozens of GIFs and the export tool is incapable of realising that the colours used most of all in the image should be preserved and not dithered. i.e. the plentiful solid white background shouldn't be exported as slightly off-white with dithering. It's a big deal because when the images are on the final web page the off-white colour is very obvious against proper solid white surrounding it on the page.

I also tried saving as PNG 8bit and the results were almost as disappointing. My workaround is to use an old copy of Photoshop, but it just makes me angry because I shouldn't have to leave Photo to achieve something so basic. (I appreciate the coding to do good palette management it isn't so basic!)

After Photo launched years ago I asked if the exporter was going to be enhanced to provide real-time previews and better indexed palette management like Photoshop... 😞 I don't suppose a 3rd party plugin for Photo exists that will export GIFs better?

Thanks.

Gary.

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