Glitches and dirt on image

[Wohlstand]

As we know, if we using sprites with transparency masks, we must made mask with black [#000000] as non-transparent, and while [#FFFFFF] colors as transparent.

But if colors not black or not white, we will see this glitch:


Try to open mask image via GIMP or other image editor, and try pipette tool:


And we see: color isn't black [must be #000000], and it also is the dirt reason on the image:


We must:
1) change color mode to RGB
2) Change to Indexed colors with B/W mode, i.e. replace ALL colors to black and white.
3) Overwrite mask image

And color must be #000000 as black and #FFFFFF as white:


and after this work, we will see:

Image was fixed.