1 #ifndef _RESAMPLE_EFFECT_H
2 #define _RESAMPLE_EFFECT_H 1
4 // High-quality image resizing, either up or down.
6 // The default scaling offered by the GPU (and as used in ResizeEffect)
7 // is bilinear (optionally mipmapped), which is not the highest-quality
8 // choice, especially for upscaling. ResampleEffect offers the three-lobed
9 // Lanczos kernel, which is among the most popular choices in image
10 // processing. While it does have its weaknesses, in particular a certain
11 // ringing/sharpening effect with artifacts that accumulate over several
12 // consecutive resizings, it is generally regarded as the best tradeoff.
14 // Works in two passes; first horizontal, then vertical (ResampleEffect,
15 // which is what the user is intended to use, instantiates two copies of
16 // SingleResamplePassEffect behind the scenes).
20 class SingleResamplePassEffect;
22 class ResampleEffect : public Effect {
26 virtual std::string effect_type_id() const { return "ResampleEffect"; }
28 // We want this for the same reason as ResizeEffect; we could end up scaling
30 virtual bool needs_texture_bounce() const { return true; }
31 virtual bool needs_srgb_primaries() const { return false; }
33 virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height);
35 virtual std::string output_fragment_shader() {
38 virtual void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) {
42 virtual void rewrite_graph(EffectChain *graph, Node *self);
43 virtual bool set_float(const std::string &key, float value);
48 SingleResamplePassEffect *hpass, *vpass;
49 int input_width, input_height, output_width, output_height;
52 class SingleResamplePassEffect : public Effect {
54 // If parent is non-NULL, calls to inform_input_size will be forwarded,
55 // so that it can inform both passes about the right input and output
57 SingleResamplePassEffect(ResampleEffect *parent);
58 ~SingleResamplePassEffect();
59 virtual std::string effect_type_id() const { return "SingleResamplePassEffect"; }
61 std::string output_fragment_shader();
63 virtual bool needs_texture_bounce() const { return true; }
64 virtual bool needs_srgb_primaries() const { return false; }
66 virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height) {
68 parent->inform_input_size(input_num, width, height);
71 virtual bool changes_output_size() const { return true; }
73 virtual void get_output_size(unsigned *width, unsigned *height) const {
74 *width = this->output_width;
75 *height = this->output_height;
78 void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
80 enum Direction { HORIZONTAL = 0, VERTICAL = 1 };
83 void update_texture(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
85 ResampleEffect *parent;
88 int input_width, input_height, output_width, output_height;
89 int last_input_width, last_input_height, last_output_width, last_output_height;
90 int src_bilinear_samples, num_loops;
94 #endif // !defined(_RESAMPLE_EFFECT_H)