@Override
    public boolean isMainFrameBufferSrgb() {
        if (!caps.contains(Caps.Srgb)) {
            return false;
        } else {
            return gl.glIsEnabled(GLExt.GL_FRAMEBUFFER_SRGB_EXT);
        }
    }
Test whether colors rendered to the main framebuffer undergo
linear-to-sRGB conversion.

@return true for conversion, false for no conversion
jme3-core/src/main/java/com/jme3/renderer/opengl/GLRenderer.java