I'm working on a simple cover art and I initially designed it like this:

enter image description here

This image is 400 x 400 pixels. However, now I have upscaled it and added some cool stuff to the image to make it look like this: enter image description here

This image is 1920 x 1080 as it's the right size for video's. I've also have some other sizes for various other uses.

The problem is that there are little upscaling arteffects from upscaling the small image. As you can see all of the squares in the bottom image have little "spikes" instead of a straight line. I tried removing these spikes by hand using the pen tool in paint.net however it's slow and I was hoping it could be done better.

As far as I know you cannot diagonally select inside paint.net otherwise I could use that to select all the spikes and then delete them.

Is there a simple way to delete the spikes and smothe the squares inside the image in paint.net?

  • 3
    Realize these aren't "errors". It is the nature of pixels to not scale smoothly.
    – Scott
    Jan 16, 2019 at 8:23
  • OK, but now that they are there, is there a way to remove them?
    – BRHSM
    Jan 16, 2019 at 8:24
  • 1
    Sorry I'm completely unfamiliar with paint.net. I can't give any guidance there. But generally, it takes careful manual editing to correct bad pixel edges. Typically you'd create such artwork with vectors rather than pixels and avoid the issue entirely.
    – Scott
    Jan 16, 2019 at 8:37
  • Yeah, I'm not really a pro and just do this for fun. Paint.net is the only program I really know well and it's pixel based.
    – BRHSM
    Jan 16, 2019 at 8:44
  • 1
    Hi. Welcome to GDSE. Have a look at Inkscape. It's a vector image editor, and it's free! Sadly, pixels based images and raster image editors don't scale up well, so best to avoid them completely for work like this.
    – Billy Kerr
    Jan 16, 2019 at 9:36

1 Answer 1


Get free G'MIC filter pack. The same is available for GIMP and Krita. Make a polygonal selection which covers your problematic squares. Apply G'MIC filter Artistic > Cutout. It simplifies edges and reduces colors. My screenshot is from Krita:

enter image description here

Cutout rounds easily corners, too. Be sure your selection covers no texts nor other already acceptable. Here's the result. My selection contained only the big black square:

enter image description here

**Not asked:**Fixing with filters generally do not give perfect results in resolution problems, the only perfect method is to draw the shape using the final resolution. It maybe is a good moment to get into the vector domain, as already suggested and avoid future problems like this. Redrawing you work in a vector program cannot take more than 20 minutes if one can use the program. Complex programs like Illustrator or Inkscape can seem frightening and the cost of Illustrator is a real obstacle for many people. But there exists simpler programs for beginners and there's low cost commercial stuff which can satisfy also professional users.


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