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ScaleAbout

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This commit is contained in:
Michael Fogleman 2016-02-20 14:45:17 -05:00
parent 52d268d7a2
commit e08199f06f
3 changed files with 16 additions and 0 deletions
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1
README.md
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@ -101,6 +101,7 @@ 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) RotateAbout(angle, x, y float64)
Shear(x, y float64) Shear(x, y float64)

4
context.go
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@ -388,6 +388,10 @@ func (dc *Context) Scale(x, y float64) {
dc.matrix = dc.matrix.Scale(x, y) dc.matrix = dc.matrix.Scale(x, y)
} }
func (dc *Context) ScaleAbout(sx, sy, x, y float64) {
dc.matrix = dc.matrix.ScaleAbout(sx, sy, x, y)
}
func (dc *Context) Rotate(angle float64) { func (dc *Context) Rotate(angle float64) {
dc.matrix = dc.matrix.Rotate(angle) dc.matrix = dc.matrix.Rotate(angle)
} }

11
matrix.go
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@ -30,6 +30,13 @@ func Scale(x, y float64) Matrix {
} }
} }
func ScaleAbout(sx, sy, x, y float64) Matrix {
a := Translate(-x, -y)
b := Scale(sx, sy)
c := Translate(x, y)
return a.Multiply(b).Multiply(c)
}
func Rotate(angle float64) Matrix { func Rotate(angle float64) Matrix {
c := math.Cos(angle) c := math.Cos(angle)
s := math.Sin(angle) s := math.Sin(angle)
@ -86,6 +93,10 @@ func (a Matrix) Scale(x, y float64) Matrix {
return Scale(x, y).Multiply(a) return Scale(x, y).Multiply(a)
} }
func (a Matrix) ScaleAbout(sx, sy, x, y float64) Matrix {
return ScaleAbout(sx, sy, x, y).Multiply(a)
}
func (a Matrix) Rotate(angle float64) Matrix { func (a Matrix) Rotate(angle float64) Matrix {
return Rotate(angle).Multiply(a) return Rotate(angle).Multiply(a)
} }