quadpixels

uniform float opacity;
uniform bool invert_color;
uniform sampler2D tex;

        void main() {
            vec4 c = texture2D(tex, gl_TexCoord[0]);
            float eps = 0.004f;
            float eps1 = 1.0f / 255.0f;
            if (invert_color)
                c = vec4(vec3(c.a, c.a, c.a) - vec3(c), c.a);

quadpixels

uniform float opacity;
uniform bool invert_color;
uniform sampler2D tex;

void main() {
	vec4 c = texture2D(tex, gl_TexCoord[0]);
	float eps = 0.004f;
	float eps1 = 1.0f / 255.0f;
	if (invert_color)
		c = vec4(vec3(c.a, c.a, c.a) - vec3(c), c.a);