There are 2 methods. The first method is a simple one, without file modifications, that filters the graphics to make it less pixelated. The second method adds a high quality image upscaling filter by Zenju “xBRZ”.

1. Launch the game
2. Press F1 or CTRL+F5 or [Mac: fn +F5] (might need to select difficulty first)
3. Click “Return to Launcher”
4. Click “Options”
5. Select “Filter Graphics”
6. Click “Apply”
7. Click “OK”
8. Click “Start”

You only need to do this once. Next time you launch the game it will remember these settings.

1. Go here: https://sourceforge.net/projects/xbrz/files/ScummVM/
2. Download: "ScummVM_2.0.0+xBRZ_Win32.zip"
3. Extract the content of the folder "scummvm-2.0.0-win32" from the above zip into:
\Steam\steamapps\common\The Curse of Monkey Island\ScummVM
4. Overwrite everything
5. Delete scummvm.exe
6. Rename “ScummVM+xBRZ.exe” to “scummvm.exe”
7. Launch the game through Steam
8. Press F1 or CTRL+F5 or [Mac: fn +F5] (might need to select difficulty first)
9. Click “Return to Launcher”
10. Click “Options”
11. Set "Graphics mode" to 'OpenGL + xBRZ scaler'
12. Select “Filter Graphics”
13. Click “Apply”
14. Click “OK”

You only need to do this once. Next time you launch the game it will remember these settings.

WARNING: The first time you set this up you might get flickering, unable to go to window mode or it might even crash. If you have any of these issues then just quit the game and launch it again from Steam. All should be working fine from then on.

UPDATE: Some people have let me know that they get micro-stuttering after doing the second method. I did not encounter this issue on windows 10 myself. BUT a solution that worked for them was to use "ScummVM_1.9.0+xBRZ" instead of 2.0.0. So if you are having stuttering try that version instead.

Example of the high quality image upscaling filter by Zenju “xBRZ”:


And another example:

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