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i3lock-color/blur_simd.c
Sebastian Frysztak 95c333cba5 SSSE3: use 16-bit weights.
Overall, I'm very happy with performance of this code, but not so much
with resulting image. It seems like integer approximations won't do.
I might remove this code altogether, so I didn't update comments.
2016-11-03 20:16:06 +01:00

265 lines
12 KiB
C

/*
* vim:ts=4:sw=4:expandtab
*
* © 2016 Sebastian Frysztak
*
* See LICENSE for licensing information
*
*/
#include "blur.h"
#include <math.h>
#include <xmmintrin.h>
#include <tmmintrin.h>
#define ALIGN16 __attribute__((aligned(16)))
#define KERNEL_SIZE 15
#define HALF_KERNEL KERNEL_SIZE / 2
// number of xmm registers needed to store
// input pixels for given kernel size
#define REGISTERS_CNT (KERNEL_SIZE + 4/2) / 4
// scaling factor for kernel coefficients.
// higher values cause desaturation.
// used in SSSE3 implementation.
#define SCALE_FACTOR 14
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++) {
for (int column = 0; column < width; column++, src++) {
__m128i rgbaIn[REGISTERS_CNT];
// handle borders
int leftBorder = column < HALF_KERNEL;
int rightBorder = column > width - HALF_KERNEL;
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 mirrors P{0..3} to fill x's,
// second one loads P{0..3}
for (; i < HALF_KERNEL - column; i++)
_rgbaIn[i] = *(src + (HALF_KERNEL - i));
for (; i < KERNEL_SIZE; i++)
_rgbaIn[i] = *(src - (HALF_KERNEL - i));
} else {
for (; i < width - column; i++)
_rgbaIn[i] = *(src + i);
for (int k = 0; i < KERNEL_SIZE; i++, k++)
_rgbaIn[i] = *(src - k);
}
for (int k = 0; k < REGISTERS_CNT; k++)
rgbaIn[k] = _mm_load_si128((__m128i*)(_rgbaIn + 4*k));
} else {
for (int k = 0; k < REGISTERS_CNT; k++)
rgbaIn[k] = _mm_loadu_si128((__m128i*)(src + 4*k - HALF_KERNEL));
}
// 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;
for (int i = 0; i < 3; i++)
{
tmp = _mm_unpacklo_epi8(rgbaIn[i], 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(rgbaIn[i], 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(rgbaIn[3], 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(rgbaIn[3], 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);
}
}
}
void blur_impl_ssse3(uint32_t *src, uint32_t *dst, int width, int height, float sigma) {
// prepare kernel
float kernelf[KERNEL_SIZE];
int16_t kernel[KERNEL_SIZE + 1];
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;
kernelf[i] = coeff * expf(-x * x / (2.0 * sigma * sigma));
sum += kernelf[i];
}
// normalize kernel
for (int i = 0; i < KERNEL_SIZE; i++)
kernelf[i] /= sum;
// round to nearest integer and convert to int
for (int i = 0; i < KERNEL_SIZE; i++)
kernel[i] = (int16_t)lrintf(kernelf[i] * (1 << SCALE_FACTOR));
kernel[KERNEL_SIZE] = 0;
// 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_ssse3(src, dst, kernel, width, height);
blur_impl_horizontal_pass_ssse3(dst, src, kernel, height, width);
}
void blur_impl_horizontal_pass_ssse3(uint32_t *src, uint32_t *dst, int16_t *kernel, int width, int height) {
__m128i _kern[2];
_kern[0] = _mm_loadu_si128((__m128i*)kernel);
_kern[1] = _mm_loadu_si128((__m128i*)(kernel + 8));
__m128i rgbaIn[REGISTERS_CNT];
for (int row = 0; row < height; row++) {
for (int column = 0; column < width; column++, src++) {
uint32_t _rgbaIn[KERNEL_SIZE] ALIGN16;
// handle borders
int leftBorder = column < HALF_KERNEL;
int rightBorder = column > width - HALF_KERNEL;
if (leftBorder || rightBorder) {
int i = 0;
if (leftBorder) {
// for kernel size 7x7 and column == 0, we have:
// x x x P0 P1 P2 P3
// first loop mirrors P{0..3} to fill x's,
// second one loads P{0..3}
for (; i < HALF_KERNEL - column; i++)
_rgbaIn[i] = *(src + (HALF_KERNEL - i));
for (; i < KERNEL_SIZE; i++)
_rgbaIn[i] = *(src - (HALF_KERNEL - i));
} else {
for (; i < width - column; i++)
_rgbaIn[i] = *(src + i);
for (int k = 0; i < KERNEL_SIZE; i++, k++)
_rgbaIn[i] = *(src - k);
}
for (int k = 0; k < REGISTERS_CNT; k++)
rgbaIn[k] = _mm_load_si128((__m128i*)(_rgbaIn + 4*k));
} else {
for (int k = 0; k < REGISTERS_CNT; k++)
rgbaIn[k] = _mm_loadu_si128((__m128i*)(src + 4*k - HALF_KERNEL));
}
// basis of this implementation is _mm_maddubs_epi16 (aka pmaddubsw).
// 'rgba' holds 16 unsigned bytes, so 4 pixels.
// 'kern' holds 16 signed bytes kernel values multiplied by (1 << SCALE_FACTOR).
// before multiplication takes place, vectors need to be prepared:
// 'rgba' is shuffled from R1B1G1A1...R4B4G4A4 to R1R2R3R4...A1A2A3A4
// 'kern' is shuffled from w1w2w3w4...w13w14w15w16 to w1w2w3w4 repeated 4 times
// then we call _mm_maddubs_epi16 and we get:
// --------------------------------------------------------------------------------------
// | R1*w1 + R2*w2 | R3*w3 + R4*w4 | G1*w1 + G2*w2 | G3*w3 + G4*w4 | repeat for B and A |
// --------------------------------------------------------------------------------------
// each 'rectangle' is a 16-byte signed int.
// then we repeat the process for the rest of input pixels,
// call _mm_hadds_epi16 to add adjacent ints and shift right to scale by SCALE_FACTOR.
__m128i rgba, rg, ba, kern;
__m128i zero = _mm_setzero_si128();
__m128i acc_rg = _mm_setzero_si128();
__m128i acc_ba = _mm_setzero_si128();
const __m128i rgba_shuf_mask = _mm_setr_epi8(0, 4, 8, 12,
1, 5, 9, 13,
2, 6, 10, 14,
3, 7, 11, 15);
const __m128i kern_shuf_mask = _mm_setr_epi8(0, 1, 2, 3,
4, 5, 6, 7,
0, 1, 2, 3,
4, 5, 6, 7);
rgba = _mm_shuffle_epi8(rgbaIn[0], rgba_shuf_mask);
rg = _mm_unpacklo_epi8(rgba, zero);
ba = _mm_unpackhi_epi8(rgba, zero);
kern = _mm_shuffle_epi8(_kern[0], kern_shuf_mask);
acc_rg = _mm_add_epi32(acc_rg, _mm_madd_epi16(rg, kern));
acc_ba = _mm_add_epi32(acc_ba, _mm_madd_epi16(ba, kern));
rgba = _mm_shuffle_epi8(rgbaIn[1], rgba_shuf_mask);
rg = _mm_unpacklo_epi8(rgba, zero);
ba = _mm_unpackhi_epi8(rgba, zero);
kern = _mm_shuffle_epi8(_mm_srli_si128(_kern[0], 8), kern_shuf_mask);
acc_rg = _mm_add_epi32(acc_rg, _mm_madd_epi16(rg, kern));
acc_ba = _mm_add_epi32(acc_ba, _mm_madd_epi16(ba, kern));
rgba = _mm_shuffle_epi8(rgbaIn[2], rgba_shuf_mask);
rg = _mm_unpacklo_epi8(rgba, zero);
ba = _mm_unpackhi_epi8(rgba, zero);
kern = _mm_shuffle_epi8(_kern[1], kern_shuf_mask);
acc_rg = _mm_add_epi32(acc_rg, _mm_madd_epi16(rg, kern));
acc_ba = _mm_add_epi32(acc_ba, _mm_madd_epi16(ba, kern));
rgba = _mm_shuffle_epi8(rgbaIn[3], rgba_shuf_mask);
rg = _mm_unpacklo_epi8(rgba, zero);
ba = _mm_unpackhi_epi8(rgba, zero);
kern = _mm_shuffle_epi8(_mm_srli_si128(_kern[1], 8), kern_shuf_mask);
acc_rg = _mm_add_epi32(acc_rg, _mm_madd_epi16(rg, kern));
acc_ba = _mm_add_epi32(acc_ba, _mm_madd_epi16(ba, kern));
rgba = _mm_hadd_epi32(acc_rg, acc_ba);
rgba = _mm_srai_epi32(rgba, SCALE_FACTOR);
// Cairo sets alpha channel to 255
// (or -1, depending how you look at it)
// this quickly overflows accumulator,
// and alpha is calculated completely wrong.
// I assume most people don't use semi-transparent
// lock screen images, so no one will mind if we
// 'correct it' by setting alpha to 255.
*(dst + height * column + row) =
_mm_cvtsi128_si32(_mm_shuffle_epi8(rgba, rgba_shuf_mask));
}
}
}