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-rw-r--r--vendor/golang.org/x/image/vp8/filter.go273
1 files changed, 273 insertions, 0 deletions
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)
+}