Fix a bug where intermediate phase outputs could get too low height.

[movit] / dither_effect.h

diff --git a/dither_effect.h b/dither_effect.h
index 943220aed55ad3dc524e4404b06ef2838f917831..cad6488921b67c5f60a3a1ac17fb97dec440b474 100644 (file)
--- a/dither_effect.h
+++ b/dither_effect.h
@@ -46,12 +46,22 @@
 #include "effect.h"
 
 class DitherEffect : public Effect {
-public:
+private:
+       // Should not be instantiated by end users;
+       // call EffectChain::set_dither_bits() instead.
        DitherEffect();
+       friend class EffectChain;
+
+public:
        ~DitherEffect();
        virtual std::string effect_type_id() const { return "DitherEffect"; }
        std::string output_fragment_shader();
 
+       // Note that if we did error diffusion, we'd actually want to diffuse the
+       // premultiplied error. However, we need to do dithering in the same
+       // space as quantization, whether that be pre- or postmultiply.
+       virtual AlphaHandling alpha_handling() const { return DONT_CARE_ALPHA_TYPE; }
+
        void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
 
 private: