My (very limited) understanding of RPGM parallaxes is that they're the background images for maps that the player can walk about on. This works like an image map. If the color of a given pixel is changed, it breaks the image map so players can walk where they shouldn't, and cannot walk where the should be able to. Lossless doesn't change the colors, lossy does.
As for the issue that
0011 was having; cruncher works by re-encoding files to more efficient formats but leaving the filename and (just as importantly) file extensions the same. I.e., it will take a 5MB image.png, re-encode it to a lossy webp image that's maybe 200KB, but the filename/extension is still image.png. This allows you to compress assets of a game without changing any of the script/code. When an image is loaded by the game, it looks at the header of the file to decode & display, not the file extension.
cwebp breaks image transparency when re-encoding webp files. I've added nconvert to the latest couple versions of cruncher as it preserves transparency. However, it's much slower than cwebp so I only set it run on files with a webp file extension.
0011 ran cruncher on a game that had already been crunched by the author, so cwebp was run on files with png extension that were actually encoded as webp already.
Hope this helps clarify?
Hello bas ,Thanks for your reply
my english is not good, sorry
1.RPGM parallaxes lossy issue
I understand what you mean.
I compress a lot of rpg maker vx ace and woldrpg game, some game parallaxes folder use jpg and png
and i use some png lossy tool to compress that parallaxes folder...
until see this bug issue, i know rpg maker mv is difference vx ace and wolfrpg *1,
but i very worry, maybe lossy parallaxes will break some game,
so i try to reproduce this issue, know how to trigger this issue in rpg maker mv
but my test project can't reproduce this.
I create a movement route in my test parallaxes picture
and change lossy picture try to trigger this issue,
but still fail, maybe i lost something in important setting.
2. webp breaks image transparency issue
this bug can reproduce,
cwebp resample will break alpha channel.
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*1 RPG Maker MV editor only support .png, but nw.js core is support .webp
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update 20200316
I think conversion to lossless webp will change png structure.
BlueSky.png(original png)
Input file: BlueSky.png | 873563 bytes
Image: 816x816 pixels | 8 bits/sample | RGB | 27773 color(s)
Delta filter: None
Filter per scanline:
000000000000000000000000000000000000000000000000
Chunks: only critical
dwebp BlueSky.webp => BlueSky.png
Input file: BlueSky.png | 614860 bytes
Image: 816x816 pixels | 8 bits/sample | RGB | 27773 color(s)
Delta filter: Paeth
Filter per scanline:
111111111111111111112122122111112111111111111111
Chunks: gAMA, sRGB