Microoptimization in calculate_scaling_weights.

Doesn't actually influence the benchmarks much, but is useful to get 100%
equivalence with the coming compute shader.

diff --git a/resample_effect.cpp b/resample_effect.cpp
index 690f15a90e6622ed9a1c53194251491622eed855..b6da2e2aeea3be8f5605d6ec10525a37c082b152 100644 (file)
--- a/resample_effect.cpp
+++ b/resample_effect.cpp
@@ -605,15 +605,16 @@ ScalingWeights calculate_scaling_weights(unsigned src_size, unsigned dst_size, f
        // to compute the destination pixel, and how many depend on the scaling factor.
        // Thus, the kernel width will vary with how much we scale.
        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;
+       const int int_radius = lrintf(LANCZOS_RADIUS / radius_scaling_factor);
+       const int src_samples = int_radius * 2 + 1;
        unique_ptr<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);
+       float inv_scaling_factor = 1.0f / scaling_factor;
        for (unsigned y = 0; y < dst_samples; ++y) {
                // Find the point around which we want to sample the source image,
                // compensating for differing pixel centers as the scale changes.
-               float center_src_y = (y + 0.5f) / scaling_factor - 0.5f;
+               float center_src_y = (y + 0.5f) * inv_scaling_factor - 0.5f;
                int base_src_y = lrintf(center_src_y);
 
                // Now sample <int_radius> pixels on each side around that point.