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I have created a graphic in GIMP with a number of layers. I have exported this image as both a .png and .jpg. When opening the image I can see there are a number of white areas and speckles that do not show on the original image.

I thought this may be something to do with differences in the layers and automatic flattening of the image, so I opened the original image again and merged down the layers to one layer.

The graphic looks perfect in original format but the speckles are still there.

Can anyone please suggest a reason for the differences and how to correct please?

Please find some images below, the GIMP Screenshot, export to Powerpoint and the full image.

GIMP screenshot Powerpoint Screenshot Full GIMP image export


Please find some images below, the GIMP Screenshot, export to Powerpoint and the full image.

GIMP screenshot Powerpoint Screenshot Full GIMP image export

  • 2
    Please post an example image. – Rafael Jan 1 at 17:37
  • Do you see consistency on the location, shape and size of those "speckles" on each export? Do four png exports (different names) and four jpeg exports of the same file. Do all the speckles look the same? If they are random, you might have bad hardware, like an overheating processor or bad memory. Otherwise we need to see examples of the original area (screenshot in Gimp) and of the matching exports please. – Martin Zaske Jan 1 at 19:11
  • The "not show" within Gimp can also be due to some of your options or settings, like you turned one of your layers invisible - but it still feeds into the exports. It will be something less obvious (to you) of course. Consider to make a copy of the project and set your Gimp to full reset-to-default user-settings and maybe find out more. – Martin Zaske Jan 1 at 19:14
  • @Rafael thank you for your response. I will try to post the original GIMP and the export. – Emma Kirkbride Jan 2 at 7:27
  • @MartinZaske thank you for replying. Yes the speckles are the same on each export and the computer is new so I know this relates to the image rather than the hardware. There are lots of layers and I have checked that I can see them all. I will try to post an image. – Emma Kirkbride Jan 2 at 7:29
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If you have coincident transparent (or even partially transparent) areas in the layers, you will see white:

  • with the PNG image, when it is displayed over a white background.
  • with the JPG image, about all the time since transparent areas are filled with the default background color (usually white) before export.

These small areas can be hard to notice in Gimp if they are smaller than the squares of the checkerboard used to show transparency.

You can use a temporary bottom layer filled with a contrasting color to locate them in Gimp before exporting (make the bottom layer invisible before export).

Fixing them depends on how you created your image. If they are at the edge of things, they are likely anti-aliasing pixels. If you colored stuff by using plain bucket-fill (or a plain color or wand selection followed by a bucket-fill), then this is the reason, because these pixels are too different from their neighbors to be included. If this is the case, state so in the comment and I'll add the proper technique to this answer.

When you have colored areas on transparency the pixels on the edges are partially transparent. This is what make the edges look smooth (this is called 'anti-aliasing'). These pixels are not selected by the wand tool or the bucket-fill, and so are not painted by default. There are two techniques to know:

  • If you want to paint the colored pixels themselves, just set the "alpha-lock" on the layer (this is the checkerboard icon at the top of the Layers list). When this is done, the (partial) transparency of the pixels is kept, so you can just paint over the pixels (brush, bucket-fill...) and the edges will be magically preserved. If you need to have a selection, make sure that the edge pixels are included in the selection.
  • If you want to fill the transparent background, set the Paint tool to Behind mode (Mode selector in the Tool options of paint tools), then paint over the layer: transparent pixels will get the new color, partially transparent pixels on the edges will be complemented with the new color (so you keep the smooth edges) and opaque pixels remain unchanged.If you need a selection, make sure it includes the edge pixels (often done with Select>Grow if the selection stoprs just before them).
  • Thank you. Your reply makes a lot of sense and I was using wand selection and bucket fill. I am trying to find out how to upload an image and will try to do so but I think you have hit the nail on the head. – Emma Kirkbride Jan 2 at 7:31
  • Edited my answer to include proper paint techniques. – xenoid Jan 2 at 17:15
  • Amazing thank you for your help that has solved my problem. – Emma Kirkbride Jan 3 at 7:42
  • 1
    Then please accept the answer ("V" mark under the vote count) to show others that there is a solution. – xenoid Jan 3 at 8:19

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