// Three-lobed Lanczos, the most common choice.
#define LANCZOS_RADIUS 3.0
-#include <GL/glew.h>
+#include <epoxy/gl.h>
#include <assert.h>
#include <limits.h>
#include <math.h>
using namespace std;
+namespace movit {
+
namespace {
float sinc(float x)
assert(false);
}
-
// For many resamplings (e.g. 640 -> 1280), we will end up with the same
// set of samples over and over again in a loop. Thus, we can compute only
// the first such loop, and then ask the card to repeat the texture for us.
int base_src_y = lrintf(center_src_y);
// Now sample <int_radius> pixels on each side around that point.
- double sum = 0.0;
for (int i = 0; i < src_samples; ++i) {
int src_y = base_src_y + i - int_radius;
float weight = lanczos_weight(radius_scaling_factor * (src_y - center_src_y), LANCZOS_RADIUS);
weights[(y * src_samples + i) * 2 + 0] = weight * radius_scaling_factor;
weights[(y * src_samples + i) * 2 + 1] = (src_y + 0.5) / float(src_size);
- sum += weights[(y * src_samples + i) * 2 + 0];
}
- // Normalize so that the sum becomes one.
- for (int i = 0; i < src_samples; ++i) {
- weights[(y * src_samples + i) * 2 + 0] /= sum;
- }
}
// Now make use of the bilinear filtering in the GPU to reduce the number of samples
src_samples,
src_samples - src_bilinear_samples);
assert(int(src_samples) - int(num_samples_saved) == src_bilinear_samples);
+
+ // Normalize so that the sum becomes one. Note that we do it twice;
+ // this sometimes helps a tiny little bit when we have many samples.
+ for (int normalize_pass = 0; normalize_pass < 2; ++normalize_pass) {
+ float sum = 0.0;
+ for (int i = 0; i < src_bilinear_samples; ++i) {
+ sum += bilinear_weights[(y * src_bilinear_samples + i) * 2 + 0];
+ }
+ for (int i = 0; i < src_bilinear_samples; ++i) {
+ bilinear_weights[(y * src_bilinear_samples + i) * 2 + 0] /= sum;
+ }
+ }
}
// Encode as a two-component texture. Note the GL_REPEAT.
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
check_error();
}
+
+} // namespace movit