A small collection of shaders that make black pixels transparent using different methods. They should work in all Game Maker Studio versions that support GLSL.
Usage
shader_set(shader)
var shader_params = shader_get_uniform(shader, "image_alpha");
shader_set_uniform_f(shader_params, image_alpha);
//Draw your sprite/surface
shader_reset()
End User Licence Agreement (EULA).