Make the PaddingEffect border 1-pixel soft.

[movit] / padding_effect.frag

diff --git a/padding_effect.frag b/padding_effect.frag
index 4f1adc1fd257f54318f38a7ada6c3e296d29089f..32ae84067503b395ecf6d27d9e90bcf75e5e091f 100644 (file)
--- a/padding_effect.frag
+++ b/padding_effect.frag
@@ -1,16 +1,24 @@
 uniform vec2 PREFIX(offset);
 uniform vec2 PREFIX(scale);
-uniform vec2 PREFIX(texcoord_min);
-uniform vec2 PREFIX(texcoord_max);
+
+uniform vec2 PREFIX(normalized_coords_to_texels);
+uniform vec2 PREFIX(offset_bottomleft);
+uniform vec2 PREFIX(offset_topright);
 
 vec4 FUNCNAME(vec2 tc) {
        tc -= PREFIX(offset);
        tc *= PREFIX(scale);
 
-       if (any(lessThan(tc, PREFIX(texcoord_min))) ||
-           any(greaterThan(tc, PREFIX(texcoord_max)))) {
+       vec2 tc_texels = tc * PREFIX(normalized_coords_to_texels);
+       vec2 coverage_bottomleft = clamp(tc_texels + PREFIX(offset_bottomleft), 0.0f, 1.0f);
+       vec2 coverare_topright = clamp(PREFIX(offset_topright) - tc_texels, 0.0f, 1.0f);
+       vec2 coverage_both = coverage_bottomleft * coverare_topright;
+       float coverage = coverage_both.x * coverage_both.y;
+
+       if (coverage <= 0.0f) {
+               // Short-circuit in case the underlying function is expensive to call.
                return PREFIX(border_color);
+       } else {
+               return mix(PREFIX(border_color), INPUT(tc), coverage);
        }
-
-       return INPUT(tc);
 }