Soooo. I have an earth map that contains all the worlds borders in red (1,0,0) and each countries with a different grayscale color (I have the country names in a file attached to the color codes). I try to add it to a shader as a texture but it doesnt matter how I set no lossy compression, no srgb, highest quality compression, maps, its still badly deteriorating the original colors. so badly that I have to set the error limit to 0.1 to get back all the borders, but then many countries will fall into the same red range. is there a way to use a pixelperfect texture to mask the main texture?
hmm, besides setting the texture to uncompressed there will always be some data loss because of a variety of reasons, one of them definitely being compression artifacts.
I would suggest using two textures in this case.
One of them would be the borders as a black/white image set to alpha compression.
The other would be the country map, again set to alpha compression.
in your shader, you can multiply the border with any color you want.
Keep in mind that you can only have so many grayscale values for your countries, you might have to split them up between two textures, both containing half (with a grayscale value between 0-1) of the countries.
That might give you enough grayscale info to get separate values for each country.
Good luck!