When using a core-only profile (by requesting a minimum version of OpenGL 3.2 at context creation), using GL_SLUMINANCE8 reports the following error:
GL_INVALID_VALUE error generated. <internalFormat> not valid.
This is understandable because of the deprecation of luminance formats. However, I would expect a GL_INTERNALFORMAT_SUPPORTED glGetInternalformativ query to then report GL_FALSE, however, this reports GL_TRUE:
GLint param = 0;
glGetInternalformativ(GL_TEXTURE_2D, GL_SLUMINANCE8, GL_INTERNALFORMAT_SUPPORTED, 1, ¶m);
I would expect that either it should report that the format is unsupported, or it should not be rejected as a format to begin with.
Apropos, is there any replacement for sluminance formats at all? Unlike regular luminance formats, it appears that the same effect cannot be achieved using swizzles since there is not a GL_SR8 format.