commit fb5dbbe661c420509c1aa71dc3e8ff742d9d59fe
parent ade9a207881fca816fe2a630b18e0d1ff2655e3e
Author: Sebastian Frysztak <sebfry@gmail.com>
Date: Sat, 22 Oct 2016 15:30:27 +0200
Add SSE2-optimized blur.
About 4-6 times faster than naive implementation.
Diffstat:
| M | blur.c | | | 3 | ++- |
| M | blur.h | | | 2 | ++ |
| A | blur_simd.c | | | 116 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
3 files changed, 120 insertions(+), 1 deletion(-)
diff --git a/blur.c b/blur.c
@@ -69,7 +69,8 @@ blur_image_surface (cairo_surface_t *surface, int radius)
dst = (uint32_t*)cairo_image_surface_get_data (tmp);
dst_stride = cairo_image_surface_get_stride (tmp);
- blur_impl_naive(src, dst, width, height, src_stride, dst_stride, 10000);
+ //blur_impl_naive(src, dst, width, height, src_stride, dst_stride, 10000);
+ blur_impl_sse2(src, dst, width, height, 2.5);
cairo_surface_destroy (tmp);
cairo_surface_flush (surface);
diff --git a/blur.h b/blur.h
@@ -6,6 +6,8 @@
void blur_image_surface (cairo_surface_t *surface, int radius);
void blur_impl_naive(uint32_t* src, uint32_t* dst, int width, int height, int src_stride, int dst_stride, int radius);
+void blur_impl_sse2(uint32_t* src, uint32_t* dst, int width, int height, float sigma);
+void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, float *kernel, int width, int height);
#endif
diff --git a/blur_simd.c b/blur_simd.c
@@ -0,0 +1,116 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * © 2016 Sebastian Frysztak
+ *
+ * See LICENSE for licensing information
+ *
+ */
+
+#include "blur.h"
+#include <math.h>
+#include <xmmintrin.h>
+
+#define ALIGN16 __attribute__((aligned(16)))
+#define KERNEL_SIZE 7
+#define HALF_KERNEL KERNEL_SIZE / 2
+
+void blur_impl_sse2(uint32_t *src, uint32_t *dst, int width, int height, float sigma) {
+ // prepare kernel
+ float kernel[KERNEL_SIZE];
+ float coeff = 1.0 / sqrtf(2 * M_PI * sigma * sigma), sum = 0;
+
+ for (int i = 0; i < KERNEL_SIZE; i++) {
+ float x = HALF_KERNEL - i;
+ kernel[i] = coeff * expf(-x * x / (2.0 * sigma * sigma));
+ sum += kernel[i];
+ }
+
+ // normalize kernel
+ for (int i = 0; i < KERNEL_SIZE; i++)
+ kernel[i] /= sum;
+
+ // horizontal pass includes image transposition:
+ // instead of writing pixel src[x] to dst[x],
+ // we write it to transposed location.
+ // (to be exact: dst[height * current_column + current_row])
+ blur_impl_horizontal_pass_sse2(src, dst, kernel, width, height);
+ blur_impl_horizontal_pass_sse2(dst, src, kernel, height, width);
+}
+
+void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, float *kernel, int width, int height) {
+ for (int row = 0; row < height; row++) {
+ // remember first and last pixel in a row
+ // (used to handle borders)
+ uint32_t firstPixel = *src;
+ uint32_t lastPixel = *(src + width - 1);
+
+ for (int column = 0; column < width; column++, src++) {
+ __m128i rgbaIn1, rgbaIn2;
+
+ // handle borders
+ int leftBorder = column < HALF_KERNEL;
+ int rightBorder = column + HALF_KERNEL >= width;
+ if (leftBorder || rightBorder) {
+ uint32_t rgbaIn[KERNEL_SIZE] ALIGN16;
+ int i = 0;
+ if (leftBorder) {
+ // for kernel size 7x7 and column == 0, we have:
+ // x x x P0 P1 P2 P3
+ // first loop fills x's with P0, second one loads P{0..3}
+ for (; i < HALF_KERNEL - column; i++)
+ rgbaIn[i] = firstPixel;
+ for (; i < KERNEL_SIZE; i++)
+ rgbaIn[i] = *(src + i - HALF_KERNEL);
+ } else {
+ for (; width < column; i++)
+ rgbaIn[i] = *(src - i - HALF_KERNEL);
+ for (; i < KERNEL_SIZE; i++)
+ rgbaIn[i] = lastPixel;
+ }
+
+ rgbaIn1 = _mm_load_si128((__m128i *)(rgbaIn));
+ rgbaIn2 = _mm_load_si128((__m128i *)(rgbaIn + 4));
+ } else {
+ rgbaIn1 = _mm_loadu_si128((__m128i *)(src - 3));
+ rgbaIn2 = _mm_loadu_si128((__m128i *)(src + 1));
+ }
+
+ // unpack each pixel, convert to float,
+ // multiply by corresponding kernel value
+ // and add to accumulator
+ __m128i tmp;
+ __m128i zero = _mm_setzero_si128();
+ __m128 rgba_ps;
+ __m128 acc = _mm_setzero_ps();
+ int counter = 0;
+
+ tmp = _mm_unpacklo_epi8(rgbaIn1, zero);
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpackhi_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+
+ tmp = _mm_unpackhi_epi8(rgbaIn1, zero);
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpackhi_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+
+ tmp = _mm_unpacklo_epi8(rgbaIn2, zero);
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpackhi_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+
+ tmp = _mm_unpackhi_epi8(rgbaIn2, zero);
+ rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero));
+ acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++])));
+
+ __m128i rgbaOut = _mm_cvtps_epi32(acc);
+ rgbaOut = _mm_packs_epi32(rgbaOut, zero);
+ rgbaOut = _mm_packus_epi16(rgbaOut, zero);
+ *(dst + height * column + row) = _mm_cvtsi128_si32(rgbaOut);
+ }
+ }
+}
