1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
|
// Copyright 2011 The Graphics-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 graphics
import (
"code.google.com/p/graphics-go/graphics/interp"
"errors"
"image"
"image/draw"
"math"
)
// I is the identity Affine transform matrix.
var I = Affine{
1, 0, 0,
0, 1, 0,
0, 0, 1,
}
// Affine is a 3x3 2D affine transform matrix.
// M(i,j) is Affine[i*3+j].
type Affine [9]float64
// Mul returns the multiplication of two affine transform matrices.
func (a Affine) Mul(b Affine) Affine {
return Affine{
a[0]*b[0] + a[1]*b[3] + a[2]*b[6],
a[0]*b[1] + a[1]*b[4] + a[2]*b[7],
a[0]*b[2] + a[1]*b[5] + a[2]*b[8],
a[3]*b[0] + a[4]*b[3] + a[5]*b[6],
a[3]*b[1] + a[4]*b[4] + a[5]*b[7],
a[3]*b[2] + a[4]*b[5] + a[5]*b[8],
a[6]*b[0] + a[7]*b[3] + a[8]*b[6],
a[6]*b[1] + a[7]*b[4] + a[8]*b[7],
a[6]*b[2] + a[7]*b[5] + a[8]*b[8],
}
}
func (a Affine) transformRGBA(dst *image.RGBA, src *image.RGBA, i interp.RGBA) error {
srcb := src.Bounds()
b := dst.Bounds()
for y := b.Min.Y; y < b.Max.Y; y++ {
for x := b.Min.X; x < b.Max.X; x++ {
sx, sy := a.pt(x, y)
if inBounds(srcb, sx, sy) {
c := i.RGBA(src, sx, sy)
off := (y-dst.Rect.Min.Y)*dst.Stride + (x-dst.Rect.Min.X)*4
dst.Pix[off+0] = c.R
dst.Pix[off+1] = c.G
dst.Pix[off+2] = c.B
dst.Pix[off+3] = c.A
}
}
}
return nil
}
// Transform applies the affine transform to src and produces dst.
func (a Affine) Transform(dst draw.Image, src image.Image, i interp.Interp) error {
if dst == nil {
return errors.New("graphics: dst is nil")
}
if src == nil {
return errors.New("graphics: src is nil")
}
// RGBA fast path.
dstRGBA, dstOk := dst.(*image.RGBA)
srcRGBA, srcOk := src.(*image.RGBA)
interpRGBA, interpOk := i.(interp.RGBA)
if dstOk && srcOk && interpOk {
return a.transformRGBA(dstRGBA, srcRGBA, interpRGBA)
}
srcb := src.Bounds()
b := dst.Bounds()
for y := b.Min.Y; y < b.Max.Y; y++ {
for x := b.Min.X; x < b.Max.X; x++ {
sx, sy := a.pt(x, y)
if inBounds(srcb, sx, sy) {
dst.Set(x, y, i.Interp(src, sx, sy))
}
}
}
return nil
}
func inBounds(b image.Rectangle, x, y float64) bool {
if x < float64(b.Min.X) || x >= float64(b.Max.X) {
return false
}
if y < float64(b.Min.Y) || y >= float64(b.Max.Y) {
return false
}
return true
}
func (a Affine) pt(x0, y0 int) (x1, y1 float64) {
fx := float64(x0) + 0.5
fy := float64(y0) + 0.5
x1 = fx*a[0] + fy*a[1] + a[2]
y1 = fx*a[3] + fy*a[4] + a[5]
return x1, y1
}
// TransformCenter applies the affine transform to src and produces dst.
// Equivalent to
// a.CenterFit(dst, src).Transform(dst, src, i).
func (a Affine) TransformCenter(dst draw.Image, src image.Image, i interp.Interp) error {
if dst == nil {
return errors.New("graphics: dst is nil")
}
if src == nil {
return errors.New("graphics: src is nil")
}
return a.CenterFit(dst.Bounds(), src.Bounds()).Transform(dst, src, i)
}
// Scale produces a scaling transform of factors x and y.
func (a Affine) Scale(x, y float64) Affine {
return a.Mul(Affine{
1 / x, 0, 0,
0, 1 / y, 0,
0, 0, 1,
})
}
// Rotate produces a clockwise rotation transform of angle, in radians.
func (a Affine) Rotate(angle float64) Affine {
s, c := math.Sincos(angle)
return a.Mul(Affine{
+c, +s, +0,
-s, +c, +0,
+0, +0, +1,
})
}
// Shear produces a shear transform by the slopes x and y.
func (a Affine) Shear(x, y float64) Affine {
d := 1 - x*y
return a.Mul(Affine{
+1 / d, -x / d, 0,
-y / d, +1 / d, 0,
0, 0, 1,
})
}
// Translate produces a translation transform with pixel distances x and y.
func (a Affine) Translate(x, y float64) Affine {
return a.Mul(Affine{
1, 0, -x,
0, 1, -y,
0, 0, +1,
})
}
// Center produces the affine transform, centered around the provided point.
func (a Affine) Center(x, y float64) Affine {
return I.Translate(-x, -y).Mul(a).Translate(x, y)
}
// CenterFit produces the affine transform, centered around the rectangles.
// It is equivalent to
// I.Translate(-<center of src>).Mul(a).Translate(<center of dst>)
func (a Affine) CenterFit(dst, src image.Rectangle) Affine {
dx := float64(dst.Min.X) + float64(dst.Dx())/2
dy := float64(dst.Min.Y) + float64(dst.Dy())/2
sx := float64(src.Min.X) + float64(src.Dx())/2
sy := float64(src.Min.Y) + float64(src.Dy())/2
return I.Translate(-sx, -sy).Mul(a).Translate(dx, dy)
}
|
