Ignore .ld files.

[movit] / dither_effect.frag

diff --git a/dither_effect.frag b/dither_effect.frag
index 930bd94fe68d3587270e04de1cb7811e1e64ce6b..6994e8467f0c9645e47d9f74ff96700028eafddf 100644 (file)
--- a/dither_effect.frag
+++ b/dither_effect.frag
@@ -1,10 +1,21 @@
 uniform sampler2D PREFIX(dither_tex);
 uniform vec2 PREFIX(tc_scale);
+uniform float PREFIX(round_fac), PREFIX(inv_round_fac);
 
 vec4 FUNCNAME(vec2 tc) {
-       // We also choose to dither alpha, just in case.
-       // Maybe it should in theory have a separate dither,
-       // but I doubt it matters much. We currently don't
-       // really handle alpha in any case.
-       return INPUT(tc) + texture2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).xxxx;
+       vec4 result = INPUT(tc);
+
+       // Don't dither alpha; the case of alpha=255 (1.0) is very important to us,
+       // and if there's any inaccuracy earlier in the chain so that it becomes e.g.
+       // 254.8, it's better to just get it rounded off than to dither and have it
+       // possibly get down to 254. This is not the case for the color components.
+       result.rgb += texture2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).xxx;
+
+       // NEED_EXPLICIT_ROUND will be #defined to 1 if the GPU has inaccurate
+       // fp32 -> int8 framebuffer rounding, and 0 otherwise.
+#if NEED_EXPLICIT_ROUND
+       result = round(result * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac));
+#endif
+
+       return result;
 }