I have an image which I wanted to set the background as transparent for, which was pretty straightforward in Pinta due to a great tutorial. But I was left with a faint whiteish grayish outline when I pasted the image over a dark background.

The advice I found online for this was to increase the "tolerance" of the bucket fill param, but this didn't work for me. Adjusting the tolerance bit-by-bit, I found tolerance of 35 still didn't get rid of the border, and tolerance 36 applied fill-transparent to parts of my actual image.

So now I'm zoomed in to 1200% and filling-transparent pixel by pixel around my image. All these pixels are shades of gray, and I just leave alone everything that's black (which delineates the outline of my image). But there's got to be a better way to "fill everything in this region lighter than black" right?

  • Tutorial can look great but can still be wrong. Anything that doesn't produce partial opacity on the edge pixels can only be sneered at. I don't know Pinta so cannot explain the "right" method. Elsewhere it is called "color to alpha".
    – xenoid
    Jun 12, 2017 at 18:01

2 Answers 2


you can use the The Free & Open Source Image Editor GIMP. GIMP is a cross-platform image editor available for GNU/Linux, OS X, Windows and more operating systems.

You can do Color -> Color to Alpha. See this Stack Exchange about Color to Alpha for an example of getting started.

Alternatively, you can Select -> Select by Color


GIMP is awesome, but it is also quite the heavyweight. I looked around for an open source bitmap editor with more features than Pinta but fewer than GIMP and came across Krita (KDE project).

It wasn't quite what I was hoping for, but it might be a good balance for others. It also has a color-to-alpha feature.

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