Add an effect for Lanczos resampling.

[movit] / resample_effect.h

diff --git a/resample_effect.h b/resample_effect.h
new file mode 100644 (file)
index 0000000..fbe5fc5
--- /dev/null
+++ b/resample_effect.h
@@ -0,0 +1,93 @@
+#ifndef _RESAMPLE_EFFECT_H
+#define _RESAMPLE_EFFECT_H 1
+
+// High-quality image resizing, either up or down.
+//
+// The default scaling offered by the GPU (and as used in ResizeEffect)
+// is bilinear (optionally mipmapped), which is not the highest-quality
+// choice, especially for upscaling. ResampleEffect offers the three-lobed
+// Lanczos kernel, which is among the most popular choices in image
+// processing. While it does have its weaknesses, in particular a certain
+// ringing/sharpening effect with artifacts that accumulate over several
+// consecutive resizings, it is generally regarded as the best tradeoff.
+//
+// Works in two passes; first horizontal, then vertical (ResampleEffect,
+// which is what the user is intended to use, instantiates two copies of
+// SingleResamplePassEffect behind the scenes).
+
+#include "effect.h"
+
+class SingleResamplePassEffect;
+
+class ResampleEffect : public Effect {
+public:
+       ResampleEffect();
+
+       virtual std::string effect_type_id() const { return "ResampleEffect"; }
+
+       // We want this for the same reason as ResizeEffect; we could end up scaling
+       // down quite a lot.
+       virtual bool needs_texture_bounce() const { return true; }
+       virtual bool needs_srgb_primaries() const { return false; }
+
+       virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height);
+
+       virtual std::string output_fragment_shader() {
+               assert(false);
+       }
+       virtual void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) {
+               assert(false);
+       }
+
+       virtual void rewrite_graph(EffectChain *graph, Node *self);
+       virtual bool set_float(const std::string &key, float value);
+       
+private:
+       void update_size();
+       
+       SingleResamplePassEffect *hpass, *vpass;
+       int input_width, input_height, output_width, output_height;
+};
+
+class SingleResamplePassEffect : public Effect {
+public:
+       // If parent is non-NULL, calls to inform_input_size will be forwarded,
+       // so that it can inform both passes about the right input and output
+       // resolutions.
+       SingleResamplePassEffect(ResampleEffect *parent);
+       ~SingleResamplePassEffect();
+       virtual std::string effect_type_id() const { return "SingleResamplePassEffect"; }
+
+       std::string output_fragment_shader();
+
+       virtual bool needs_texture_bounce() const { return true; }
+       virtual bool needs_srgb_primaries() const { return false; }
+
+       virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height) {
+               if (parent != NULL) {
+                       parent->inform_input_size(input_num, width, height);
+               }
+       }
+       virtual bool changes_output_size() const { return true; }
+
+       virtual void get_output_size(unsigned *width, unsigned *height) const {
+               *width = this->output_width;
+               *height = this->output_height;
+       }
+
+       void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
+       
+       enum Direction { HORIZONTAL = 0, VERTICAL = 1 };
+
+private:
+       void update_texture(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
+
+       ResampleEffect *parent;
+       Direction direction;
+       GLuint texnum;
+       int input_width, input_height, output_width, output_height;
+       int last_input_width, last_input_height, last_output_width, last_output_height;
+       int src_samples;
+};
+
+#endif // !defined(_RESAMPLE_EFFECT_H)