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()
//
// 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;
// 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,
}
}
+ // 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<int>(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();
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_RG32F, 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)
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.
projects / movit / commitdiff