From 5215390259a3b39c576b63853240bbf1f1f6dc46 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Sat, 27 Oct 2012 21:17:45 +0200 Subject: [PATCH] Revert "Use the bilinear sampling trick in ResampleEffect." On second thought, this doesn't really look correct; there are some artifacts. This reverts commit 1a06994ccdeedba95a1bdd2c3c12bb54a7a897f9. --- resample_effect.cpp | 83 ++++------------------------------------ resample_effect.h | 2 +- resample_effect_test.cpp | 2 +- 3 files changed, 9 insertions(+), 78 deletions(-) diff --git a/resample_effect.cpp b/resample_effect.cpp index a176074..5b01686 100644 --- a/resample_effect.cpp +++ b/resample_effect.cpp @@ -40,51 +40,6 @@ 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; - } - 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; - combine_two_samples(w1, w2, &offset, &total_weight); - - // 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() @@ -198,6 +153,8 @@ 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; @@ -274,7 +231,7 @@ 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); - int src_samples = int_radius * 2 + 1; + 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, @@ -291,31 +248,6 @@ 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(); @@ -327,11 +259,10 @@ 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_RG32F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_FLOAT, bilinear_weights); + glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_samples, dst_samples, 0, GL_RG, GL_FLOAT, weights); check_error(); delete[] weights; - delete[] bilinear_weights; } void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) @@ -356,13 +287,13 @@ 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_bilinear_samples); + set_uniform_int(glsl_program_num, prefix, "num_samples", src_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_bilinear_samples); - set_uniform_float(glsl_program_num, prefix, "sample_x_offset", 0.5f / src_bilinear_samples); + 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); // We specifically do not want mipmaps on the input texture; // they break minification. diff --git a/resample_effect.h b/resample_effect.h index 5867f25..1424bbf 100644 --- a/resample_effect.h +++ b/resample_effect.h @@ -87,7 +87,7 @@ private: 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_bilinear_samples, num_loops; + int src_samples, num_loops; float slice_height; }; diff --git a/resample_effect_test.cpp b/resample_effect_test.cpp index f05bb8a..462f5c9 100644 --- a/resample_effect_test.cpp +++ b/resample_effect_test.cpp @@ -91,7 +91,7 @@ TEST(ResampleEffectTest, DownscaleByTwoGetsCorrectPixelCenters) { float expected_data[size * size] = { 0.0045, -0.0067, -0.0598, -0.0067, 0.0045, -0.0067, 0.0099, 0.0886, 0.0099, -0.0067, - -0.0598, 0.0886, 0.7871, 0.0886, -0.0598, + -0.0598, 0.0886, 0.7930, 0.0886, -0.0598, -0.0067, 0.0099, 0.0886, 0.0099, -0.0067, 0.0045, -0.0067, -0.0598, -0.0067, 0.0045, }; -- 2.39.2