namespace {
+template<class T>
+struct Tap {
+ T weight;
+ T pos;
+};
+
float sinc(float x)
{
if (fabs(x) < 1e-6) {
return a;
}
-unsigned combine_samples(float *src, float *dst, unsigned num_src_samples, unsigned max_samples_saved)
+unsigned combine_samples(Tap<float> *src, Tap<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];
+ dst[j] = src[i];
}
if (i == num_src_samples - 1) {
continue;
}
- float w1 = src[i * 2 + 0];
- float w2 = src[(i + 1) * 2 + 0];
+ float w1 = src[i].weight;
+ float w2 = src[i + 1].weight;
if (w1 * w2 < 0.0f) {
// Differing signs; cannot combine.
continue;
}
- float pos1 = src[i * 2 + 1];
- float pos2 = src[(i + 1) * 2 + 1];
+ float pos1 = src[i].pos;
+ float pos2 = src[i + 1].pos;
assert(pos2 > pos1);
float offset, total_weight, sum_sq_error;
// 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);
+ dst[j].weight = total_weight;
+ dst[j].pos = pos1 + offset * (pos2 - pos1);
}
++i; // Skip the next sample.
float radius_scaling_factor = min(scaling_factor, 1.0f);
int int_radius = lrintf(LANCZOS_RADIUS / radius_scaling_factor);
int src_samples = int_radius * 2 + 1;
- float *weights = new float[dst_samples * src_samples * 2];
+ Tap<float> *weights = new Tap<float>[dst_samples * src_samples];
float subpixel_offset = offset - lrintf(offset); // The part not covered by whole_pixel_offset.
assert(subpixel_offset >= -0.5f && subpixel_offset <= 0.5f);
for (unsigned y = 0; y < dst_samples; ++y) {
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 - subpixel_offset), 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);
+ weights[y * src_samples + i].weight = weight * radius_scaling_factor;
+ weights[y * src_samples + i].pos = (src_y + 0.5) / float(src_size);
}
}
// 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);
+ unsigned num_samples_saved = combine_samples(weights + y * src_samples, NULL, src_samples, UINT_MAX);
src_bilinear_samples = 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];
- fp16_int_t *bilinear_weights_fp16 = new fp16_int_t[dst_samples * src_bilinear_samples * 2];
+ Tap<float> *bilinear_weights = new Tap<float>[dst_samples * src_bilinear_samples];
+ Tap<fp16_int_t> *bilinear_weights_fp16 = new Tap<fp16_int_t>[dst_samples * src_bilinear_samples];
for (unsigned y = 0; y < dst_samples; ++y) {
- float *bilinear_weights_ptr = bilinear_weights + (y * src_bilinear_samples) * 2;
- fp16_int_t *bilinear_weights_fp16_ptr = bilinear_weights_fp16 + (y * src_bilinear_samples) * 2;
+ Tap<float> *bilinear_weights_ptr = bilinear_weights + y * src_bilinear_samples;
+ Tap<fp16_int_t> *bilinear_weights_fp16_ptr = bilinear_weights_fp16 + y * src_bilinear_samples;
unsigned num_samples_saved = combine_samples(
- weights + (y * src_samples) * 2,
+ weights + y * src_samples,
bilinear_weights_ptr,
src_samples,
src_samples - src_bilinear_samples);
// Convert to fp16.
for (int i = 0; i < src_bilinear_samples; ++i) {
- bilinear_weights_fp16_ptr[i * 2 + 0] = fp64_to_fp16(bilinear_weights_ptr[i * 2 + 0]);
- bilinear_weights_fp16_ptr[i * 2 + 1] = fp64_to_fp16(bilinear_weights_ptr[i * 2 + 1]);
+ bilinear_weights_fp16_ptr[i].weight = fp64_to_fp16(bilinear_weights_ptr[i].weight);
+ bilinear_weights_fp16_ptr[i].pos = fp64_to_fp16(bilinear_weights_ptr[i].pos);
}
// Normalize so that the sum becomes one. Note that we do it twice;
for (int normalize_pass = 0; normalize_pass < 2; ++normalize_pass) {
double sum = 0.0;
for (int i = 0; i < src_bilinear_samples; ++i) {
- sum += fp16_to_fp64(bilinear_weights_fp16_ptr[i * 2 + 0]);
+ sum += fp16_to_fp64(bilinear_weights_fp16_ptr[i].weight);
}
for (int i = 0; i < src_bilinear_samples; ++i) {
- bilinear_weights_fp16_ptr[i * 2 + 0] = fp64_to_fp16(
- fp16_to_fp64(bilinear_weights_fp16_ptr[i * 2 + 0]) / sum);
+ bilinear_weights_fp16_ptr[i].weight = fp64_to_fp16(
+ fp16_to_fp64(bilinear_weights_fp16_ptr[i].weight) / sum);
}
}
}