From e1e8d058a33f7566f9c565d04b0d8b56f9645c35 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Wed, 25 Apr 2018 09:28:54 +0200 Subject: add vendor --- vendor/golang.org/x/image/vp8/filter.go | 273 ++++++++++++++++++++++++++++++++ 1 file changed, 273 insertions(+) create mode 100644 vendor/golang.org/x/image/vp8/filter.go (limited to 'vendor/golang.org/x/image/vp8/filter.go') diff --git a/vendor/golang.org/x/image/vp8/filter.go b/vendor/golang.org/x/image/vp8/filter.go new file mode 100644 index 0000000..e34a811 --- /dev/null +++ b/vendor/golang.org/x/image/vp8/filter.go @@ -0,0 +1,273 @@ +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package vp8 + +// filter2 modifies a 2-pixel wide or 2-pixel high band along an edge. +func filter2(pix []byte, level, index, iStep, jStep int) { + for n := 16; n > 0; n, index = n-1, index+iStep { + p1 := int(pix[index-2*jStep]) + p0 := int(pix[index-1*jStep]) + q0 := int(pix[index+0*jStep]) + q1 := int(pix[index+1*jStep]) + if abs(p0-q0)<<1+abs(p1-q1)>>1 > level { + continue + } + a := 3*(q0-p0) + clamp127(p1-q1) + a1 := clamp15((a + 4) >> 3) + a2 := clamp15((a + 3) >> 3) + pix[index-1*jStep] = clamp255(p0 + a2) + pix[index+0*jStep] = clamp255(q0 - a1) + } +} + +// filter246 modifies a 2-, 4- or 6-pixel wide or high band along an edge. +func filter246(pix []byte, n, level, ilevel, hlevel, index, iStep, jStep int, fourNotSix bool) { + for ; n > 0; n, index = n-1, index+iStep { + p3 := int(pix[index-4*jStep]) + p2 := int(pix[index-3*jStep]) + p1 := int(pix[index-2*jStep]) + p0 := int(pix[index-1*jStep]) + q0 := int(pix[index+0*jStep]) + q1 := int(pix[index+1*jStep]) + q2 := int(pix[index+2*jStep]) + q3 := int(pix[index+3*jStep]) + if abs(p0-q0)<<1+abs(p1-q1)>>1 > level { + continue + } + if abs(p3-p2) > ilevel || + abs(p2-p1) > ilevel || + abs(p1-p0) > ilevel || + abs(q1-q0) > ilevel || + abs(q2-q1) > ilevel || + abs(q3-q2) > ilevel { + continue + } + if abs(p1-p0) > hlevel || abs(q1-q0) > hlevel { + // Filter 2 pixels. + a := 3*(q0-p0) + clamp127(p1-q1) + a1 := clamp15((a + 4) >> 3) + a2 := clamp15((a + 3) >> 3) + pix[index-1*jStep] = clamp255(p0 + a2) + pix[index+0*jStep] = clamp255(q0 - a1) + } else if fourNotSix { + // Filter 4 pixels. + a := 3 * (q0 - p0) + a1 := clamp15((a + 4) >> 3) + a2 := clamp15((a + 3) >> 3) + a3 := (a1 + 1) >> 1 + pix[index-2*jStep] = clamp255(p1 + a3) + pix[index-1*jStep] = clamp255(p0 + a2) + pix[index+0*jStep] = clamp255(q0 - a1) + pix[index+1*jStep] = clamp255(q1 - a3) + } else { + // Filter 6 pixels. + a := clamp127(3*(q0-p0) + clamp127(p1-q1)) + a1 := (27*a + 63) >> 7 + a2 := (18*a + 63) >> 7 + a3 := (9*a + 63) >> 7 + pix[index-3*jStep] = clamp255(p2 + a3) + pix[index-2*jStep] = clamp255(p1 + a2) + pix[index-1*jStep] = clamp255(p0 + a1) + pix[index+0*jStep] = clamp255(q0 - a1) + pix[index+1*jStep] = clamp255(q1 - a2) + pix[index+2*jStep] = clamp255(q2 - a3) + } + } +} + +// simpleFilter implements the simple filter, as specified in section 15.2. +func (d *Decoder) simpleFilter() { + for mby := 0; mby < d.mbh; mby++ { + for mbx := 0; mbx < d.mbw; mbx++ { + f := d.perMBFilterParams[d.mbw*mby+mbx] + if f.level == 0 { + continue + } + l := int(f.level) + yIndex := (mby*d.img.YStride + mbx) * 16 + if mbx > 0 { + filter2(d.img.Y, l+4, yIndex, d.img.YStride, 1) + } + if f.inner { + filter2(d.img.Y, l, yIndex+0x4, d.img.YStride, 1) + filter2(d.img.Y, l, yIndex+0x8, d.img.YStride, 1) + filter2(d.img.Y, l, yIndex+0xc, d.img.YStride, 1) + } + if mby > 0 { + filter2(d.img.Y, l+4, yIndex, 1, d.img.YStride) + } + if f.inner { + filter2(d.img.Y, l, yIndex+d.img.YStride*0x4, 1, d.img.YStride) + filter2(d.img.Y, l, yIndex+d.img.YStride*0x8, 1, d.img.YStride) + filter2(d.img.Y, l, yIndex+d.img.YStride*0xc, 1, d.img.YStride) + } + } + } +} + +// normalFilter implements the normal filter, as specified in section 15.3. +func (d *Decoder) normalFilter() { + for mby := 0; mby < d.mbh; mby++ { + for mbx := 0; mbx < d.mbw; mbx++ { + f := d.perMBFilterParams[d.mbw*mby+mbx] + if f.level == 0 { + continue + } + l, il, hl := int(f.level), int(f.ilevel), int(f.hlevel) + yIndex := (mby*d.img.YStride + mbx) * 16 + cIndex := (mby*d.img.CStride + mbx) * 8 + if mbx > 0 { + filter246(d.img.Y, 16, l+4, il, hl, yIndex, d.img.YStride, 1, false) + filter246(d.img.Cb, 8, l+4, il, hl, cIndex, d.img.CStride, 1, false) + filter246(d.img.Cr, 8, l+4, il, hl, cIndex, d.img.CStride, 1, false) + } + if f.inner { + filter246(d.img.Y, 16, l, il, hl, yIndex+0x4, d.img.YStride, 1, true) + filter246(d.img.Y, 16, l, il, hl, yIndex+0x8, d.img.YStride, 1, true) + filter246(d.img.Y, 16, l, il, hl, yIndex+0xc, d.img.YStride, 1, true) + filter246(d.img.Cb, 8, l, il, hl, cIndex+0x4, d.img.CStride, 1, true) + filter246(d.img.Cr, 8, l, il, hl, cIndex+0x4, d.img.CStride, 1, true) + } + if mby > 0 { + filter246(d.img.Y, 16, l+4, il, hl, yIndex, 1, d.img.YStride, false) + filter246(d.img.Cb, 8, l+4, il, hl, cIndex, 1, d.img.CStride, false) + filter246(d.img.Cr, 8, l+4, il, hl, cIndex, 1, d.img.CStride, false) + } + if f.inner { + filter246(d.img.Y, 16, l, il, hl, yIndex+d.img.YStride*0x4, 1, d.img.YStride, true) + filter246(d.img.Y, 16, l, il, hl, yIndex+d.img.YStride*0x8, 1, d.img.YStride, true) + filter246(d.img.Y, 16, l, il, hl, yIndex+d.img.YStride*0xc, 1, d.img.YStride, true) + filter246(d.img.Cb, 8, l, il, hl, cIndex+d.img.CStride*0x4, 1, d.img.CStride, true) + filter246(d.img.Cr, 8, l, il, hl, cIndex+d.img.CStride*0x4, 1, d.img.CStride, true) + } + } + } +} + +// filterParam holds the loop filter parameters for a macroblock. +type filterParam struct { + // The first three fields are thresholds used by the loop filter to smooth + // over the edges and interior of a macroblock. level is used by both the + // simple and normal filters. The inner level and high edge variance level + // are only used by the normal filter. + level, ilevel, hlevel uint8 + // inner is whether the inner loop filter cannot be optimized out as a + // no-op for this particular macroblock. + inner bool +} + +// computeFilterParams computes the loop filter parameters, as specified in +// section 15.4. +func (d *Decoder) computeFilterParams() { + for i := range d.filterParams { + baseLevel := d.filterHeader.level + if d.segmentHeader.useSegment { + baseLevel = d.segmentHeader.filterStrength[i] + if d.segmentHeader.relativeDelta { + baseLevel += d.filterHeader.level + } + } + + for j := range d.filterParams[i] { + p := &d.filterParams[i][j] + p.inner = j != 0 + level := baseLevel + if d.filterHeader.useLFDelta { + // The libwebp C code has a "TODO: only CURRENT is handled for now." + level += d.filterHeader.refLFDelta[0] + if j != 0 { + level += d.filterHeader.modeLFDelta[0] + } + } + if level <= 0 { + p.level = 0 + continue + } + if level > 63 { + level = 63 + } + ilevel := level + if d.filterHeader.sharpness > 0 { + if d.filterHeader.sharpness > 4 { + ilevel >>= 2 + } else { + ilevel >>= 1 + } + if x := int8(9 - d.filterHeader.sharpness); ilevel > x { + ilevel = x + } + } + if ilevel < 1 { + ilevel = 1 + } + p.ilevel = uint8(ilevel) + p.level = uint8(2*level + ilevel) + if d.frameHeader.KeyFrame { + if level < 15 { + p.hlevel = 0 + } else if level < 40 { + p.hlevel = 1 + } else { + p.hlevel = 2 + } + } else { + if level < 15 { + p.hlevel = 0 + } else if level < 20 { + p.hlevel = 1 + } else if level < 40 { + p.hlevel = 2 + } else { + p.hlevel = 3 + } + } + } + } +} + +// intSize is either 32 or 64. +const intSize = 32 << (^uint(0) >> 63) + +func abs(x int) int { + // m := -1 if x < 0. m := 0 otherwise. + m := x >> (intSize - 1) + + // In two's complement representation, the negative number + // of any number (except the smallest one) can be computed + // by flipping all the bits and add 1. This is faster than + // code with a branch. + // See Hacker's Delight, section 2-4. + return (x ^ m) - m +} + +func clamp15(x int) int { + if x < -16 { + return -16 + } + if x > 15 { + return 15 + } + return x +} + +func clamp127(x int) int { + if x < -128 { + return -128 + } + if x > 127 { + return 127 + } + return x +} + +func clamp255(x int) uint8 { + if x < 0 { + return 0 + } + if x > 255 { + return 255 + } + return uint8(x) +} -- cgit v1.2.3