Remove C++11 dependency from ResampleEffect.

[movit] / dither_effect.frag

diff --git a/dither_effect.frag b/dither_effect.frag
index f9c6ad13c443e1919c4506790159c9134106d8a7..f12530dbdd7cd904b8ae820928c66cf471259f20 100644 (file)
--- a/dither_effect.frag
+++ b/dither_effect.frag
@@ -1,12 +1,43 @@
-uniform sampler2D PREFIX(dither_tex);
-uniform vec2 PREFIX(tc_scale);
-uniform float PREFIX(round_fac), PREFIX(inv_round_fac);
+// Implicit uniforms:
+// uniform sampler2D PREFIX(dither_tex);
+// uniform vec2 PREFIX(tc_scale);
+// uniform float PREFIX(round_fac), PREFIX(inv_round_fac);
+
+// See footer.frag for details about this if statement.
+#ifndef YCBCR_ALSO_OUTPUT_RGBA
+#define YCBCR_ALSO_OUTPUT_RGBA 0
+#endif
+
+#if YCBCR_ALSO_OUTPUT_RGBA
+
+// There are two values to dither; otherwise, exactly the same as the algorithm below
+// (so comments are not duplicated).
+
+vec4[2] FUNCNAME(vec2 tc) {
+       vec4[2] result = INPUT(tc);
+       float d = tex2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).x;
+       result[0].rgb += vec3(d);
+       result[1].rgb += vec3(d);
+
+#if NEED_EXPLICIT_ROUND
+       result[0] = round(result[0] * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac));
+       result[1] = round(result[1] * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac));
+#endif
+
+       return result;
+}
+
+#else
 
 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.
-       vec4 result = INPUT(tc) + texture2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).xxxx;
+       vec4 result = INPUT(tc);
+       float d = tex2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).x;
+
+       // 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 += vec3(d);
 
        // NEED_EXPLICIT_ROUND will be #defined to 1 if the GPU has inaccurate
        // fp32 -> int8 framebuffer rounding, and 0 otherwise.
@@ -16,3 +47,5 @@ vec4 FUNCNAME(vec2 tc) {
 
        return result;
 }
+
+#endif