Bug 340088

After a 8 Bits document is converted into 16 Bits Float, save and re-open it when OpenGL is ON, you will see pixelated glitches around the edges over a transparent background, especially when zoomed OUT as much as possible. Editing the picture will not fix this. The new generated edges will glitch out as well. Changing Krita's Monitor profile from sRGB built-in to System Monitor Profile seems to turn the glitches from yellow to grey.

Doesn't happen on:
1) Very soft edges;
2) Pictures of 8 Bits per channel;
3) Pictures created as 16 Bit Float per channel natively;
4) Pictures converted to 16 Bits Float per channel, with background not 100% transparent, 1% white (99% transparency) works fine;
5) When zoomed in more than 200%, you cannot see the glitches anymore;
6) When OpenGL is OFF
7) Immediately when a 8 Bits picture is converted into 16 Bits (it glitches next time you open it)

Reproducible: Always

Steps to Reproduce:
1. Create a new document, A4 (300dpi) / RGB / 8 Bits / sRGB
2. Turn white background layer invisible
3. On the layer above, use Elliptical Selection tool to make a very large selection, then fill it with pure green
4. Menu > Image > Convert Image Color Space > Depth = 16 Bits Float, LCMS optimization does not matter
5. Save and close Krita
6. Open the saved file
7. Zoom OUT to max and you will see yellow pixelated glitches around the edges over transparent background.

Actual Results:  
8 Bits to 16 Bits Float conversion causes pixelated glitches on the edges over transparent BG when OpenGL is ON

Expected Results:  
8 Bits to 16 Bits Float conversion does not cause pixelated glitches on the edges over transparent BG when OpenGL is ON