To those complaining that it doesn't run in general (all black): You'll need to setup a viewport, just like in the example room.
I had a problem specifically with the HTML5 export. Gamemaker seems to be doing a weird implicit type conversion which results in errors.
Simply adding a real() call to line 83 in the crt object's Create event solved the HTML problem: texture_set_stage(sampler_id, sprite_get_texture(mask_type, real(mask_rgbx_repeat_on_threes)));
Great shader, thanks for the work!











