1 #ifndef _DECONVOLUTION_SHARPEN_EFFECT_H
2 #define _DECONVOLUTION_SHARPEN_EFFECT_H 1
4 // DeconvolutionSharpenEffect is an effect that sharpens by way of deconvolution
5 // (i.e., trying to reverse the blur kernel, as opposed to just boosting high
6 // frequencies), more specifically by FIR Wiener filters. It is the same
7 // algorithm as used by the (now largely abandoned) Refocus plug-in for GIMP,
8 // and I suspect the same as in Photoshop's “Smart Sharpen” filter.
9 // The implementation is, however, distinct from either.
11 // The effect gives generally better results than unsharp masking, but can be very
12 // GPU intensive, and requires a fair bit of tweaking to get good results without
13 // ringing and/or excessive noise. It should be mentioned that for the larger
14 // convolutions (e.g. R approaching 10), we should probably move to FFT-based
15 // convolution algorithms, especially as Mesa's shader compiler starts having
16 // problems compiling our shader.
18 // We follow the same book as Refocus was implemented from, namely
20 // Jain, Anil K.: “Fundamentals of Digital Image Processing”, Prentice Hall, 1988.
24 #include <Eigen/Dense>
26 class DeconvolutionSharpenEffect : public Effect {
28 DeconvolutionSharpenEffect();
29 virtual std::string effect_type_id() const { return "DeconvolutionSharpenEffect"; }
30 std::string output_fragment_shader();
32 virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height)
35 this->height = height;
38 void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
42 unsigned width, height;
44 // The maximum radius of the (de)convolution kernel.
45 // Note that since this extends both ways, and we also have a center element,
46 // the actual convolution matrix will be (2R + 1) x (2R + 1).
48 // Must match the definition in the shader, and as such, cannot be set once
49 // the chain has been finalized.
52 // The parameters. Typical OK values are circle_radius = 2, gaussian_radius = 0
53 // (ie., blur is assumed to be a 2px circle), correlation = 0.95, and noise = 0.01.
54 // Note that once the radius starts going too far past R, you will get nonsensical results.
55 float circle_radius, gaussian_radius, correlation, noise;
57 // The deconvolution kernel, and the parameters last time we did an update.
60 float last_circle_radius, last_gaussian_radius, last_correlation, last_noise;
62 void update_deconvolution_kernel();
65 #endif // !defined(_DECONVOLUTION_SHARPEN_EFFECT_H)