X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=resample_effect.cpp;h=f0c57c78ad772d42a20bb50c887199ea77c34ab5;hp=5b016861fafac36d0c55c4133323f1a6315b1846;hb=ad66f9714e4a36008c341355700272a52484a785;hpb=5215390259a3b39c576b63853240bbf1f1f6dc46 diff --git a/resample_effect.cpp b/resample_effect.cpp index 5b01686..f0c57c7 100644 --- a/resample_effect.cpp +++ b/resample_effect.cpp @@ -1,13 +1,17 @@ // Three-lobed Lanczos, the most common choice. #define LANCZOS_RADIUS 3.0 -#include +#include #include +#include +#include +#include +#include -#include "resample_effect.h" #include "effect_chain.h" +#include "effect_util.h" +#include "resample_effect.h" #include "util.h" -#include "opengl.h" namespace { @@ -40,6 +44,61 @@ unsigned gcd(unsigned a, unsigned b) return a; } +unsigned combine_samples(float *src, float *dst, unsigned num_src_samples, unsigned max_samples_saved) +{ + unsigned num_samples_saved = 0; + for (unsigned i = 0, j = 0; i < num_src_samples; ++i, ++j) { + // Copy the sample directly; it will be overwritten later if we can combine. + if (dst != NULL) { + dst[j * 2 + 0] = src[i * 2 + 0]; + dst[j * 2 + 1] = src[i * 2 + 1]; + } + + if (i == num_src_samples - 1) { + // Last sample; cannot combine. + continue; + } + assert(num_samples_saved <= max_samples_saved); + if (num_samples_saved == max_samples_saved) { + // We could maybe save more here, but other rows can't, so don't bother. + continue; + } + + float w1 = src[i * 2 + 0]; + float w2 = src[(i + 1) * 2 + 0]; + if (w1 * w2 < 0.0f) { + // Differing signs; cannot combine. + continue; + } + + float pos1 = src[i * 2 + 1]; + float pos2 = src[(i + 1) * 2 + 1]; + assert(pos2 > pos1); + + float offset, total_weight, sum_sq_error; + combine_two_samples(w1, w2, &offset, &total_weight, &sum_sq_error); + + // If the interpolation error is larger than that of about sqrt(2) of + // a level at 8-bit precision, don't combine. (You'd think 1.0 was enough, + // but since the artifacts are not really random, they can get quite + // visible. On the other hand, going to 0.25f, I can see no change at + // all with 8-bit output, so it would not seem to be worth it.) + if (sum_sq_error > 0.5f / (256.0f * 256.0f)) { + continue; + } + + // OK, we can combine this and the next sample. + if (dst != NULL) { + dst[j * 2 + 0] = total_weight; + dst[j * 2 + 1] = pos1 + offset * (pos2 - pos1); + } + + ++i; // Skip the next sample. + ++num_samples_saved; + } + return num_samples_saved; +} + } // namespace ResampleEffect::ResampleEffect() @@ -51,9 +110,9 @@ ResampleEffect::ResampleEffect() // The first blur pass will forward resolution information to us. hpass = new SingleResamplePassEffect(this); - hpass->set_int("direction", SingleResamplePassEffect::HORIZONTAL); + CHECK(hpass->set_int("direction", SingleResamplePassEffect::HORIZONTAL)); vpass = new SingleResamplePassEffect(NULL); - vpass->set_int("direction", SingleResamplePassEffect::VERTICAL); + CHECK(vpass->set_int("direction", SingleResamplePassEffect::VERTICAL)); update_size(); } @@ -153,8 +212,6 @@ std::string SingleResamplePassEffect::output_fragment_shader() // // For horizontal scaling, we fill in the exact same texture; // the shader just interprets is differently. -// -// TODO: Support optimization using free linear sampling, like in BlurEffect. void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) { unsigned src_size, dst_size; @@ -231,7 +288,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std // Thus, the kernel width will vary with how much we scale. float radius_scaling_factor = std::min(float(dst_size) / float(src_size), 1.0f); int int_radius = lrintf(LANCZOS_RADIUS / radius_scaling_factor); - src_samples = int_radius * 2 + 1; + int src_samples = int_radius * 2 + 1; float *weights = new float[dst_samples * src_samples * 2]; for (unsigned y = 0; y < dst_samples; ++y) { // Find the point around which we want to sample the source image, @@ -248,6 +305,31 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std } } + // Now make use of the bilinear filtering in the GPU to reduce the number of samples + // we need to make. This is a bit more complex than BlurEffect since we cannot combine + // two neighboring samples if their weights have differing signs, so we first need to + // figure out the maximum number of samples. Then, we downconvert all the weights to + // that number -- we could have gone for a variable-length system, but this is simpler, + // and the gains would probably be offset by the extra cost of checking when to stop. + // + // The greedy strategy for combining samples is optimal. + src_bilinear_samples = 0; + for (unsigned y = 0; y < dst_samples; ++y) { + unsigned num_samples_saved = combine_samples(weights + (y * src_samples) * 2, NULL, src_samples, UINT_MAX); + src_bilinear_samples = std::max(src_bilinear_samples, src_samples - num_samples_saved); + } + + // Now that we know the right width, actually combine the samples. + float *bilinear_weights = new float[dst_samples * src_bilinear_samples * 2]; + for (unsigned y = 0; y < dst_samples; ++y) { + unsigned num_samples_saved = combine_samples( + weights + (y * src_samples) * 2, + bilinear_weights + (y * src_bilinear_samples) * 2, + src_samples, + src_samples - src_bilinear_samples); + assert(int(src_samples) - int(num_samples_saved) == src_bilinear_samples); + } + // Encode as a two-component texture. Note the GL_REPEAT. glActiveTexture(GL_TEXTURE0 + *sampler_num); check_error(); @@ -259,16 +341,22 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std check_error(); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); check_error(); - glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_samples, dst_samples, 0, GL_RG, GL_FLOAT, weights); + glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_FLOAT, bilinear_weights); check_error(); delete[] weights; + delete[] bilinear_weights; } void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) { Effect::set_gl_state(glsl_program_num, prefix, sampler_num); + assert(input_width > 0); + assert(input_height > 0); + assert(output_width > 0); + assert(output_height > 0); + if (input_width != last_input_width || input_height != last_input_height || output_width != last_output_width || @@ -287,13 +375,13 @@ void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std:: set_uniform_int(glsl_program_num, prefix, "sample_tex", *sampler_num); ++sampler_num; - set_uniform_int(glsl_program_num, prefix, "num_samples", src_samples); + set_uniform_int(glsl_program_num, prefix, "num_samples", src_bilinear_samples); set_uniform_float(glsl_program_num, prefix, "num_loops", num_loops); set_uniform_float(glsl_program_num, prefix, "slice_height", slice_height); // Instructions for how to convert integer sample numbers to positions in the weight texture. - set_uniform_float(glsl_program_num, prefix, "sample_x_scale", 1.0f / src_samples); - set_uniform_float(glsl_program_num, prefix, "sample_x_offset", 0.5f / src_samples); + set_uniform_float(glsl_program_num, prefix, "sample_x_scale", 1.0f / src_bilinear_samples); + set_uniform_float(glsl_program_num, prefix, "sample_x_offset", 0.5f / src_bilinear_samples); // We specifically do not want mipmaps on the input texture; // they break minification.