Alpha/Color issues with Gosu/Ashton

[Aerotune]

I'm having some issues with getting Gosu and Ashton to render clean images.

Without Ashton I've found out that drawing a Gosu::Image on any non-whole position or up/down scaling makes some dark edges appear. It's not noticeable on a blurry picture.

With Ashton a shader that does nothing on the pyramides it messes up the colors and alpha channel. (gl_FragColor = texture2D(in_Texture, var_TexCoord); I'm not opengl savvy, am I doing something wrong?)

I've made a test case project here: https://github.com/Aerotune/ashton_alpha_issue
I'm using Gosu 0.7.50, Ashton 0.1.3 and I'm running Mac OS 10.7.5

[bil-bas]

Well, first off, best bug report ever!

You are right in your assumption - the effect should be identical with or without the post-processing shader. Although I haven't looked at Ashton in a long while, I've been doing a lot of work with OpenGL lately, so maybe I can divine a cause.

Note that Ashton 0.1.4 was released a couple of days ago and uses a newer version of OpenGL gem which fixes some things in Ashton (probably not this, though). Also Gosu 0.8, but all that does is move to SDL2 as a backend and I think is still a bit buggy.

[Aerotune]

OK I just tried updating Ashton to 0.1.4 and I still have the same dark edges.

[Aerotune]

Updating to Gosu 0.8.2 doesn't change anything as well.

[bil-bas]

I didn't particularly expect it to, but worth a try.