diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/image/jpeg/fdct.go | 34 | ||||
| -rw-r--r-- | src/image/jpeg/idct.go | 88 |
2 files changed, 63 insertions, 59 deletions
diff --git a/src/image/jpeg/fdct.go b/src/image/jpeg/fdct.go index 201a5abd0b..c7a973ec3c 100644 --- a/src/image/jpeg/fdct.go +++ b/src/image/jpeg/fdct.go @@ -86,14 +86,16 @@ const ( func fdct(b *block) { // Pass 1: process rows. for y := 0; y < 8; y++ { - x0 := b[y*8+0] - x1 := b[y*8+1] - x2 := b[y*8+2] - x3 := b[y*8+3] - x4 := b[y*8+4] - x5 := b[y*8+5] - x6 := b[y*8+6] - x7 := b[y*8+7] + y8 := y * 8 + s := b[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857 + x0 := s[0] + x1 := s[1] + x2 := s[2] + x3 := s[3] + x4 := s[4] + x5 := s[5] + x6 := s[6] + x7 := s[7] tmp0 := x0 + x7 tmp1 := x1 + x6 @@ -110,12 +112,12 @@ func fdct(b *block) { tmp2 = x2 - x5 tmp3 = x3 - x4 - b[y*8+0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits - b[y*8+4] = (tmp10 - tmp11) << pass1Bits + s[0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits + s[4] = (tmp10 - tmp11) << pass1Bits z1 := (tmp12 + tmp13) * fix_0_541196100 z1 += 1 << (constBits - pass1Bits - 1) - b[y*8+2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits) - b[y*8+6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits) + s[2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits) + s[6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits) tmp10 = tmp0 + tmp3 tmp11 = tmp1 + tmp2 @@ -134,10 +136,10 @@ func fdct(b *block) { tmp12 += z1 tmp13 += z1 - b[y*8+1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits) - b[y*8+3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits) - b[y*8+5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits) - b[y*8+7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits) + s[1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits) + s[3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits) + s[5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits) + s[7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits) } // Pass 2: process columns. // We remove pass1Bits scaling, but leave results scaled up by an overall factor of 8. diff --git a/src/image/jpeg/idct.go b/src/image/jpeg/idct.go index 46fcaecb79..a3957c8ada 100644 --- a/src/image/jpeg/idct.go +++ b/src/image/jpeg/idct.go @@ -73,30 +73,31 @@ func idct(src *block) { // Horizontal 1-D IDCT. for y := 0; y < 8; y++ { y8 := y * 8 + s := src[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857 // If all the AC components are zero, then the IDCT is trivial. - if src[y8+1] == 0 && src[y8+2] == 0 && src[y8+3] == 0 && - src[y8+4] == 0 && src[y8+5] == 0 && src[y8+6] == 0 && src[y8+7] == 0 { - dc := src[y8+0] << 3 - src[y8+0] = dc - src[y8+1] = dc - src[y8+2] = dc - src[y8+3] = dc - src[y8+4] = dc - src[y8+5] = dc - src[y8+6] = dc - src[y8+7] = dc + if s[1] == 0 && s[2] == 0 && s[3] == 0 && + s[4] == 0 && s[5] == 0 && s[6] == 0 && s[7] == 0 { + dc := s[0] << 3 + s[0] = dc + s[1] = dc + s[2] = dc + s[3] = dc + s[4] = dc + s[5] = dc + s[6] = dc + s[7] = dc continue } // Prescale. - x0 := (src[y8+0] << 11) + 128 - x1 := src[y8+4] << 11 - x2 := src[y8+6] - x3 := src[y8+2] - x4 := src[y8+1] - x5 := src[y8+7] - x6 := src[y8+5] - x7 := src[y8+3] + x0 := (s[0] << 11) + 128 + x1 := s[4] << 11 + x2 := s[6] + x3 := s[2] + x4 := s[1] + x5 := s[7] + x6 := s[5] + x7 := s[3] // Stage 1. x8 := w7 * (x4 + x5) @@ -126,14 +127,14 @@ func idct(src *block) { x4 = (r2*(x4-x5) + 128) >> 8 // Stage 4. - src[y8+0] = (x7 + x1) >> 8 - src[y8+1] = (x3 + x2) >> 8 - src[y8+2] = (x0 + x4) >> 8 - src[y8+3] = (x8 + x6) >> 8 - src[y8+4] = (x8 - x6) >> 8 - src[y8+5] = (x0 - x4) >> 8 - src[y8+6] = (x3 - x2) >> 8 - src[y8+7] = (x7 - x1) >> 8 + s[0] = (x7 + x1) >> 8 + s[1] = (x3 + x2) >> 8 + s[2] = (x0 + x4) >> 8 + s[3] = (x8 + x6) >> 8 + s[4] = (x8 - x6) >> 8 + s[5] = (x0 - x4) >> 8 + s[6] = (x3 - x2) >> 8 + s[7] = (x7 - x1) >> 8 } // Vertical 1-D IDCT. @@ -141,16 +142,17 @@ func idct(src *block) { // Similar to the horizontal 1-D IDCT case, if all the AC components are zero, then the IDCT is trivial. // However, after performing the horizontal 1-D IDCT, there are typically non-zero AC components, so // we do not bother to check for the all-zero case. + s := src[x : x+57 : x+57] // Small cap improves performance, see https://golang.org/issue/27857 // Prescale. - y0 := (src[8*0+x] << 8) + 8192 - y1 := src[8*4+x] << 8 - y2 := src[8*6+x] - y3 := src[8*2+x] - y4 := src[8*1+x] - y5 := src[8*7+x] - y6 := src[8*5+x] - y7 := src[8*3+x] + y0 := (s[8*0] << 8) + 8192 + y1 := s[8*4] << 8 + y2 := s[8*6] + y3 := s[8*2] + y4 := s[8*1] + y5 := s[8*7] + y6 := s[8*5] + y7 := s[8*3] // Stage 1. y8 := w7*(y4+y5) + 4 @@ -180,13 +182,13 @@ func idct(src *block) { y4 = (r2*(y4-y5) + 128) >> 8 // Stage 4. - src[8*0+x] = (y7 + y1) >> 14 - src[8*1+x] = (y3 + y2) >> 14 - src[8*2+x] = (y0 + y4) >> 14 - src[8*3+x] = (y8 + y6) >> 14 - src[8*4+x] = (y8 - y6) >> 14 - src[8*5+x] = (y0 - y4) >> 14 - src[8*6+x] = (y3 - y2) >> 14 - src[8*7+x] = (y7 - y1) >> 14 + s[8*0] = (y7 + y1) >> 14 + s[8*1] = (y3 + y2) >> 14 + s[8*2] = (y0 + y4) >> 14 + s[8*3] = (y8 + y6) >> 14 + s[8*4] = (y8 - y6) >> 14 + s[8*5] = (y0 - y4) >> 14 + s[8*6] = (y3 - y2) >> 14 + s[8*7] = (y7 - y1) >> 14 } } |