From 500caaeda74dd9c660279036293f4b2997cf0b03 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Sat, 9 Sep 2017 09:42:37 +0200 Subject: Add vendor --- vendor/golang.org/x/image/vp8/idct.go | 98 +++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 vendor/golang.org/x/image/vp8/idct.go (limited to 'vendor/golang.org/x/image/vp8/idct.go') diff --git a/vendor/golang.org/x/image/vp8/idct.go b/vendor/golang.org/x/image/vp8/idct.go new file mode 100644 index 0000000..929af2c --- /dev/null +++ b/vendor/golang.org/x/image/vp8/idct.go @@ -0,0 +1,98 @@ +// Copyright 2011 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 + +// This file implements the inverse Discrete Cosine Transform and the inverse +// Walsh Hadamard Transform (WHT), as specified in sections 14.3 and 14.4. + +func clip8(i int32) uint8 { + if i < 0 { + return 0 + } + if i > 255 { + return 255 + } + return uint8(i) +} + +func (z *Decoder) inverseDCT4(y, x, coeffBase int) { + const ( + c1 = 85627 // 65536 * cos(pi/8) * sqrt(2). + c2 = 35468 // 65536 * sin(pi/8) * sqrt(2). + ) + var m [4][4]int32 + for i := 0; i < 4; i++ { + a := int32(z.coeff[coeffBase+0]) + int32(z.coeff[coeffBase+8]) + b := int32(z.coeff[coeffBase+0]) - int32(z.coeff[coeffBase+8]) + c := (int32(z.coeff[coeffBase+4])*c2)>>16 - (int32(z.coeff[coeffBase+12])*c1)>>16 + d := (int32(z.coeff[coeffBase+4])*c1)>>16 + (int32(z.coeff[coeffBase+12])*c2)>>16 + m[i][0] = a + d + m[i][1] = b + c + m[i][2] = b - c + m[i][3] = a - d + coeffBase++ + } + for j := 0; j < 4; j++ { + dc := m[0][j] + 4 + a := dc + m[2][j] + b := dc - m[2][j] + c := (m[1][j]*c2)>>16 - (m[3][j]*c1)>>16 + d := (m[1][j]*c1)>>16 + (m[3][j]*c2)>>16 + z.ybr[y+j][x+0] = clip8(int32(z.ybr[y+j][x+0]) + (a+d)>>3) + z.ybr[y+j][x+1] = clip8(int32(z.ybr[y+j][x+1]) + (b+c)>>3) + z.ybr[y+j][x+2] = clip8(int32(z.ybr[y+j][x+2]) + (b-c)>>3) + z.ybr[y+j][x+3] = clip8(int32(z.ybr[y+j][x+3]) + (a-d)>>3) + } +} + +func (z *Decoder) inverseDCT4DCOnly(y, x, coeffBase int) { + dc := (int32(z.coeff[coeffBase+0]) + 4) >> 3 + for j := 0; j < 4; j++ { + for i := 0; i < 4; i++ { + z.ybr[y+j][x+i] = clip8(int32(z.ybr[y+j][x+i]) + dc) + } + } +} + +func (z *Decoder) inverseDCT8(y, x, coeffBase int) { + z.inverseDCT4(y+0, x+0, coeffBase+0*16) + z.inverseDCT4(y+0, x+4, coeffBase+1*16) + z.inverseDCT4(y+4, x+0, coeffBase+2*16) + z.inverseDCT4(y+4, x+4, coeffBase+3*16) +} + +func (z *Decoder) inverseDCT8DCOnly(y, x, coeffBase int) { + z.inverseDCT4DCOnly(y+0, x+0, coeffBase+0*16) + z.inverseDCT4DCOnly(y+0, x+4, coeffBase+1*16) + z.inverseDCT4DCOnly(y+4, x+0, coeffBase+2*16) + z.inverseDCT4DCOnly(y+4, x+4, coeffBase+3*16) +} + +func (d *Decoder) inverseWHT16() { + var m [16]int32 + for i := 0; i < 4; i++ { + a0 := int32(d.coeff[384+0+i]) + int32(d.coeff[384+12+i]) + a1 := int32(d.coeff[384+4+i]) + int32(d.coeff[384+8+i]) + a2 := int32(d.coeff[384+4+i]) - int32(d.coeff[384+8+i]) + a3 := int32(d.coeff[384+0+i]) - int32(d.coeff[384+12+i]) + m[0+i] = a0 + a1 + m[8+i] = a0 - a1 + m[4+i] = a3 + a2 + m[12+i] = a3 - a2 + } + out := 0 + for i := 0; i < 4; i++ { + dc := m[0+i*4] + 3 + a0 := dc + m[3+i*4] + a1 := m[1+i*4] + m[2+i*4] + a2 := m[1+i*4] - m[2+i*4] + a3 := dc - m[3+i*4] + d.coeff[out+0] = int16((a0 + a1) >> 3) + d.coeff[out+16] = int16((a3 + a2) >> 3) + d.coeff[out+32] = int16((a0 - a1) >> 3) + d.coeff[out+48] = int16((a3 - a2) >> 3) + out += 64 + } +} -- cgit v1.2.3