mirror of https://github.com/nothings/stb.git
stb_image: SSE2 YCbCr->RGB kernel
This commit is contained in:
Fabian Giesen
parent
d95f7acb32
commit
aabf2c5c49
126
stb_image.h
126
stb_image.h
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@ -25,7 +25,7 @@
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- decode from memory or through FILE (define STBI_NO_STDIO to remove code)
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- decode from arbitrary I/O callbacks
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- overridable dequantizing-IDCT, YCbCr-to-RGB conversion (define STBI_SIMD)
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- SIMD acceleration on x86/x64
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Latest revisions:
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1.48 (2014-12-14) fix incorrectly-named assert()
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@ -326,20 +326,6 @@ STBIDEF char *stbi_zlib_decode_noheader_malloc(const char *buffer, int len, int
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STBIDEF int stbi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);
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// define faster low-level operations (typically SIMD support)
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#ifdef STBI_SIMD
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typedef void (*stbi_YCbCr_to_RGB_run)(stbi_uc *output, stbi_uc const *y, stbi_uc const *cb, stbi_uc const *cr, int count, int step);
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// compute a conversion from YCbCr to RGB
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// 'count' pixels
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// write pixels to 'output'; each pixel is 'step' bytes (either 3 or 4; if 4, write '255' as 4th), order R,G,B
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// y: Y input channel
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// cb: Cb input channel; scale/biased to be 0..255
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// cr: Cr input channel; scale/biased to be 0..255
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STBIDEF void stbi_install_YCbCr_to_RGB(stbi_YCbCr_to_RGB_run func);
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#endif // STBI_SIMD
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#ifdef __cplusplus
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}
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#endif
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@ -1074,6 +1060,7 @@ typedef struct
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// kernels
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void (*idct_block_kernel)(stbi_uc *out, int out_stride, short data[64]);
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void (*YCbCr_to_RGB_kernel)(stbi_uc *out, const stbi_uc *y, const stbi_uc *pcb, const stbi_uc *pcr, int count, int step);
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} stbi__jpeg;
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static int stbi__build_huffman(stbi__huffman *h, int *count)
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@ -1355,15 +1342,6 @@ stbi_inline static stbi_uc stbi__clamp(int x)
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t1 += p2+p4; \
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t0 += p1+p3;
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#ifdef STBI_SIMD
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static unsigned short stbi__dq_ones[64] = {
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1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
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1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
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1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
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1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1,1,
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};
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#endif
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// .344 seconds on 3*anemones.jpg
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static void stbi__idct_block(stbi_uc *out, int out_stride, short data[64])
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{
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@ -2045,12 +2023,94 @@ static void stbi__YCbCr_to_RGB_row(stbi_uc *out, const stbi_uc *y, const stbi_uc
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}
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}
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#ifdef STBI_SIMD
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static stbi_YCbCr_to_RGB_run stbi__YCbCr_installed = stbi__YCbCr_to_RGB_row;
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STBIDEF void stbi_install_YCbCr_to_RGB(stbi_YCbCr_to_RGB_run func)
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#ifdef STBI_SSE2
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static void stbi__YCbCr_to_RGB_sse2(stbi_uc *out, stbi_uc const *y, stbi_uc const *pcb, stbi_uc const *pcr, int count, int step)
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{
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stbi__YCbCr_installed = func;
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int i = 0;
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// step == 3 is pretty ugly on the final interleave, and i'm not convinced
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// it's useful in practice (you wouldn't use it for textures, for example).
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// so just accelerate step == 4 case.
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//
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// note: unlike the IDCT, this isn't bit-identical to the integer version.
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if (step == 4) {
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// this is a fairly straightforward implementation and not super-optimized.
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__m128i signflip = _mm_set1_epi8(-0x80);
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__m128i cr_const0 = _mm_set1_epi16((short) ( 1.40200f*4096.0f));
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__m128i cr_const1 = _mm_set1_epi16((short) (-0.71414f*4096.0f));
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__m128i cb_const0 = _mm_set1_epi16((short) (-0.34414f*4096.0f));
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__m128i cb_const1 = _mm_set1_epi16((short) ( 1.77200f*4096.0f));
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__m128i y_bias = _mm_set1_epi16(8);
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__m128i xw = _mm_set1_epi16(255);
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for (; i+7 < count; i += 8) {
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// load
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__m128i zero = _mm_setzero_si128();
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__m128i y_bytes = _mm_loadl_epi64((__m128i *) (y+i));
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__m128i cr_bytes = _mm_loadl_epi64((__m128i *) (pcr+i));
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__m128i cb_bytes = _mm_loadl_epi64((__m128i *) (pcb+i));
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__m128i cr_bias = _mm_xor_si128(cr_bytes, signflip); // -128
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__m128i cb_bias = _mm_xor_si128(cb_bytes, signflip); // -128
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// unpack to short (and left-shift cr, cb by 8)
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__m128i yw = _mm_unpacklo_epi8(y_bytes, zero);
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__m128i crw = _mm_unpacklo_epi8(_mm_setzero_si128(), cr_bias);
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__m128i cbw = _mm_unpacklo_epi8(_mm_setzero_si128(), cb_bias);
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// color transform
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__m128i yws = _mm_slli_epi16(yw, 4);
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__m128i cr0 = _mm_mulhi_epi16(cr_const0, crw);
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__m128i cb0 = _mm_mulhi_epi16(cb_const0, cbw);
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__m128i ywb = _mm_add_epi16(yws, y_bias);
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__m128i cb1 = _mm_mulhi_epi16(cbw, cb_const1);
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__m128i cr1 = _mm_mulhi_epi16(crw, cr_const1);
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__m128i rws = _mm_add_epi16(cr0, ywb);
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__m128i gwt = _mm_add_epi16(cb0, ywb);
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__m128i bws = _mm_add_epi16(ywb, cb1);
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__m128i gws = _mm_add_epi16(gwt, cr1);
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// descale
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__m128i rw = _mm_srai_epi16(rws, 4);
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__m128i bw = _mm_srai_epi16(bws, 4);
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__m128i gw = _mm_srai_epi16(gws, 4);
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// back to byte, set up for transpose
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__m128i brb = _mm_packus_epi16(rw, bw);
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__m128i gxb = _mm_packus_epi16(gw, xw);
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// transpose to interleave channels
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__m128i t0 = _mm_unpacklo_epi8(brb, gxb);
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__m128i t1 = _mm_unpackhi_epi8(brb, gxb);
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__m128i o0 = _mm_unpacklo_epi16(t0, t1);
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__m128i o1 = _mm_unpackhi_epi16(t0, t1);
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// store
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_mm_storeu_si128((__m128i *) (out + 0), o0);
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_mm_storeu_si128((__m128i *) (out + 16), o1);
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out += 32;
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}
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}
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for (; i < count; ++i) {
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int y_fixed = (y[i] << 16) + 32768; // rounding
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int r,g,b;
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int cr = pcr[i] - 128;
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int cb = pcb[i] - 128;
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r = y_fixed + cr*float2fixed(1.40200f);
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g = y_fixed - cr*float2fixed(0.71414f) - cb*float2fixed(0.34414f);
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b = y_fixed + cb*float2fixed(1.77200f);
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r >>= 16;
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g >>= 16;
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b >>= 16;
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if ((unsigned) r > 255) { if (r < 0) r = 0; else r = 255; }
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if ((unsigned) g > 255) { if (g < 0) g = 0; else g = 255; }
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if ((unsigned) b > 255) { if (b < 0) b = 0; else b = 255; }
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out[0] = (stbi_uc)r;
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out[1] = (stbi_uc)g;
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out[2] = (stbi_uc)b;
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out[3] = 255;
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out += step;
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}
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}
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#endif
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@ -2058,10 +2118,12 @@ STBIDEF void stbi_install_YCbCr_to_RGB(stbi_YCbCr_to_RGB_run func)
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static void stbi__setup_jpeg(stbi__jpeg *j)
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{
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j->idct_block_kernel = stbi__idct_block;
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j->YCbCr_to_RGB_kernel = stbi__YCbCr_to_RGB_row;
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#ifdef STBI_SSE2
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if (stbi__sse2_available()) {
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j->idct_block_kernel = stbi__idct_sse2;
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j->YCbCr_to_RGB_kernel = stbi__YCbCr_to_RGB_sse2;
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}
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#endif
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}
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@ -2167,11 +2229,7 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
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if (n >= 3) {
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stbi_uc *y = coutput[0];
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if (z->s->img_n == 3) {
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#ifdef STBI_SIMD
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stbi__YCbCr_installed(out, y, coutput[1], coutput[2], z->s->img_x, n);
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#else
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stbi__YCbCr_to_RGB_row(out, y, coutput[1], coutput[2], z->s->img_x, n);
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#endif
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z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
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} else
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for (i=0; i < z->s->img_x; ++i) {
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out[0] = out[1] = out[2] = y[i];
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