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cleanup, add commets

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This commit is contained in:
wsw 2016-11-21 14:51:07 +08:00
parent 1aa57065bb
commit 298fbeaa77
1 changed files with 9 additions and 18 deletions
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27
gradient.go
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@ -36,9 +36,6 @@ type Gradient interface {
// Linear Gradient
type linearGradient struct {
x0, y0, x1, y1 float64
dx, dy float64
mag float64
px0, py0 float64
stops stops
}
@ -48,8 +45,8 @@ func (g *linearGradient) ColorAt(x, y int) color.Color {
}
fx, fy := float64(x), float64(y)
x0, y0 := g.x0, g.y0
dx, dy := g.dx, g.dy
x0, y0, x1, y1 := g.x0, g.y0, g.x1, g.y1
dx, dy := x1-x0, y1-y0
// Horizontal
if dy == 0 && dx != 0 {
@ -61,15 +58,15 @@ func (g *linearGradient) ColorAt(x, y int) color.Color {
return getColor((fy-y0)/dy, g.stops)
}
px0, py0 := g.px0, g.py0
mag := g.mag
s0 := (px0-x0)*(fy-y0) - (py0-y0)*(fx-x0)
if s0 > 0 {
// Dot product
s0 := dx*(fx-x0) + dy*(fy-y0)
if s0 < 0 {
return g.stops[0].color
}
u := ((fx-x0)*(px0-x0) + (fy-y0)*(py0-y0)) / (mag * mag)
x2, y2 := x0+u*(px0-x0), y0+u*(py0-y0)
// Calculate distance to (x0,y0) alone (x0,y0)->(x1,y1)
mag := math.Hypot(dx, dy)
u := ((fx-x0)*-dy + (fy-y0)*dx) / (mag * mag)
x2, y2 := x0+u*-dy, y0+u*dx
d := math.Hypot(fx-x2, fy-y2) / mag
return getColor(d, g.stops)
}
@ -80,15 +77,9 @@ func (g *linearGradient) AddColorStop(offset float64, color color.Color) {
}
func NewLinearGradient(x0, y0, x1, y1 float64) Gradient {
dx, dy := x1-x0, y1-y0
mag := math.Hypot(dx, dy)
px0, py0 := x0-dy, y0+dx
g := &linearGradient{
x0: x0, y0: y0,
x1: x1, y1: y1,
dx: dx, dy: dy,
px0: px0, py0: py0,
mag: mag,
}
return g
}