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ShearAbout

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This commit is contained in:
Michael Fogleman 2016-02-20 14:53:33 -05:00
parent 1d5fd3d775
commit b77c5f2881
3 changed files with 20 additions and 4 deletions
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5
README.md
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@ -101,10 +101,11 @@ SetFillRule(fillRule FillRule)
Identity() Identity()
Translate(x, y float64) Translate(x, y float64)
Scale(x, y float64) Scale(x, y float64)
ScaleAbout(sx, sy, x, y float64)
Rotate(angle float64) Rotate(angle float64)
RotateAbout(angle, x, y float64)
Shear(x, y float64) Shear(x, y float64)
ScaleAbout(sx, sy, x, y float64)
RotateAbout(angle, x, y float64)
ShearAbout(sx, sy, x, y float64)
TransformPoint(x, y float64) (tx, ty float64) TransformPoint(x, y float64) (tx, ty float64)
InvertY() InvertY()
Push() Push()

4
context.go
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@ -404,6 +404,10 @@ func (dc *Context) Shear(x, y float64) {
dc.matrix = dc.matrix.Shear(x, y) dc.matrix = dc.matrix.Shear(x, y)
} }
func (dc *Context) ShearAbout(sx, sy, x, y float64) {
dc.matrix = dc.matrix.ShearAbout(sx, sy, x, y)
}
func (dc *Context) TransformPoint(x, y float64) (tx, ty float64) { func (dc *Context) TransformPoint(x, y float64) (tx, ty float64) {
return dc.matrix.TransformPoint(x, y) return dc.matrix.TransformPoint(x, y)
} }

15
matrix.go
View File

@ -56,12 +56,19 @@ func RotateAbout(angle, x, y float64) Matrix {
func Shear(x, y float64) Matrix { func Shear(x, y float64) Matrix {
return Matrix{ return Matrix{
1, x, 1, y,
y, 1, x, 1,
0, 0, 0, 0,
} }
} }
func ShearAbout(sx, sy, x, y float64) Matrix {
a := Translate(-x, -y)
b := Shear(sx, sy)
c := Translate(x, y)
return a.Multiply(b).Multiply(c)
}
func (a Matrix) Multiply(b Matrix) Matrix { func (a Matrix) Multiply(b Matrix) Matrix {
return Matrix{ return Matrix{
a.XX*b.XX + a.YX*b.XY, a.XX*b.XX + a.YX*b.XY,
@ -108,3 +115,7 @@ func (a Matrix) RotateAbout(angle, x, y float64) Matrix {
func (a Matrix) Shear(x, y float64) Matrix { func (a Matrix) Shear(x, y float64) Matrix {
return Shear(x, y).Multiply(a) return Shear(x, y).Multiply(a)
} }
func (a Matrix) ShearAbout(sx, sy, x, y float64) Matrix {
return ShearAbout(sx, sy, x, y).Multiply(a)
}