MOHAWK: Myst ME: Wrong map colors in the GOG Polish version

[iGom]

An error pops up when I try to view the map in GOG Polish version of Myst

ERROR: Could not decode Myst bitmap!

Edit:
someone has written about it before
​https://forums.scummvm.org/viewtopic.php?t=13980&p=87348

[iGom]

I just checked the retail Polish version (not via ScummVM) and the map is present, but still crashes in ScummVM.

​https://discord.com/channels/581224060529148060/581224061091446795/795393141578006610

[dafioram]

Confirmed for polish version. The other versions work just fine.

[digitall]

Pushed a partial fix for this as commit ​https://github.com/scummvm/scummvm/commit/3853bcf2628912e98681fda26d121c2b1f161c7a

The relevant image is uncompressed i.e. no LZSS compression which is indicated by an
uncompressed size field of 0. This was not being handled correctly hence why this failed.

However, there is still a further problem here as the colors for the map are inverted with a white edging (not black as expected) and purple island (not green). There is no
color palette and the image is 24bpp, so not sure why that is happening, but no crash at least.

[iGom]

I can confirm that fix works also with the retail Polish version.
Checked in the latest daily build.

[digitall]

iGom: To be clear, are the colors of the map correct for the retail Polish version?

[iGom]

Oh, sorry for didn't mention that, no, colors are still inverted.

[tag2015]

Fixed in commit ​fd86bf0

[digitall]

This bug was reopened as the fix was limited to the Myst Island Map i.e. Card 9934, but this issue is present on the maps on the other islands as well, hence iGom has added savegames to allow these to be tested. The fix required should be just to add the other card numbers to the workaround / fix line.

[digitall]

It should be noted that I have tested this with Myst ME - 25th Anniversary from GOG in Polish language and even with this fix being triggered (I added a debug to check this), the colours on the Myst map do not look quite right i.e. Green is OK, but the mountains are blue, not brown so I think the colorspace is off still. Will attach a screenshot.

[digitall]

Image from Myst ME 25th Showing Colors Still Off With Fix

[digitall]

Screenshot attached.

[tag2015]

@digitall did a quick test now, it seems that the fix only works in OpenGL mode (in SDL Surface mode, the colors are still off). I wonder if the culprit is convertToInPlace

[digitall]

Have expanded the workaround / conversion to cover all Map images in the ME Polish version in commit ​541badb

This doesn't fix the color conversion / palette issues but the workaround code now applies to all the affected slides.

[tag2015]

Thanks! Definitely cleaner than checking all the ids

[digitall]

Further notes, on Linux x86_64 with SDL Surface output, the colors are off, but they are fine if I switch to OpenGL output.

[tag2015]

Yes, same thing on Win10. This was clearly a half-baked effort on my end, it seems the fix isn't as trivial as anticipated.
If anybody wants to attempt a proper fix, please go ahead (I'm really not focusing on this engine right now)