Add an effect for Lanczos resampling.

[movit] / resample_effect.frag

diff --git a/resample_effect.frag b/resample_effect.frag
new file mode 100644 (file)
index 0000000..6aac29d
--- /dev/null
+++ b/resample_effect.frag
@@ -0,0 +1,38 @@
+// DIRECTION_VERTICAL will be #defined to 1 if we are scaling vertically,
+// and 0 otherwise.
+
+uniform sampler2D PREFIX(sample_tex);
+uniform int PREFIX(num_samples);
+uniform float PREFIX(sample_x_scale);
+uniform float PREFIX(sample_x_offset);
+
+// Sample a single weight. First fetch information about where to sample
+// and the weight from sample_tex, and then read the pixel itself.
+vec4 PREFIX(do_sample)(vec2 tc, int i)
+{
+       vec2 sample_tc;
+       sample_tc.x = float(i) * PREFIX(sample_x_scale) + PREFIX(sample_x_offset);
+#if DIRECTION_VERTICAL
+       sample_tc.y = tc.y;
+#else
+       sample_tc.y = tc.x;
+#endif
+       vec2 sample = texture2D(PREFIX(sample_tex), sample_tc).rg;
+
+#if DIRECTION_VERTICAL
+       tc.y = sample.g;
+#else
+       tc.x = sample.g;
+#endif
+       return vec4(sample.r) * INPUT(tc);
+}
+
+vec4 FUNCNAME(vec2 tc) {
+       vec4 sum = PREFIX(do_sample)(tc, 0);
+       for (int i = 1; i < PREFIX(num_samples); ++i) {
+               sum += PREFIX(do_sample)(tc, i);
+       }
+       return sum;
+}
+
+#undef DIRECTION_VERTICAL