status-go/vendor/github.com/fogleman/gg/gradient.go

203 lines
3.8 KiB
Go

package gg
import (
"image/color"
"math"
"sort"
)
type stop struct {
pos float64
color color.Color
}
type stops []stop
// Len satisfies the Sort interface.
func (s stops) Len() int {
return len(s)
}
// Less satisfies the Sort interface.
func (s stops) Less(i, j int) bool {
return s[i].pos < s[j].pos
}
// Swap satisfies the Sort interface.
func (s stops) Swap(i, j int) {
s[i], s[j] = s[j], s[i]
}
type Gradient interface {
Pattern
AddColorStop(offset float64, color color.Color)
}
// Linear Gradient
type linearGradient struct {
x0, y0, x1, y1 float64
stops stops
}
func (g *linearGradient) ColorAt(x, y int) color.Color {
if len(g.stops) == 0 {
return color.Transparent
}
fx, fy := float64(x), float64(y)
x0, y0, x1, y1 := g.x0, g.y0, g.x1, g.y1
dx, dy := x1-x0, y1-y0
// Horizontal
if dy == 0 && dx != 0 {
return getColor((fx-x0)/dx, g.stops)
}
// Vertical
if dx == 0 && dy != 0 {
return getColor((fy-y0)/dy, g.stops)
}
// Dot product
s0 := dx*(fx-x0) + dy*(fy-y0)
if s0 < 0 {
return g.stops[0].color
}
// 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)
}
func (g *linearGradient) AddColorStop(offset float64, color color.Color) {
g.stops = append(g.stops, stop{pos: offset, color: color})
sort.Sort(g.stops)
}
func NewLinearGradient(x0, y0, x1, y1 float64) Gradient {
g := &linearGradient{
x0: x0, y0: y0,
x1: x1, y1: y1,
}
return g
}
// Radial Gradient
type circle struct {
x, y, r float64
}
type radialGradient struct {
c0, c1, cd circle
a, inva float64
mindr float64
stops stops
}
func dot3(x0, y0, z0, x1, y1, z1 float64) float64 {
return x0*x1 + y0*y1 + z0*z1
}
func (g *radialGradient) ColorAt(x, y int) color.Color {
if len(g.stops) == 0 {
return color.Transparent
}
// copy from pixman's pixman-radial-gradient.c
dx, dy := float64(x)+0.5-g.c0.x, float64(y)+0.5-g.c0.y
b := dot3(dx, dy, g.c0.r, g.cd.x, g.cd.y, g.cd.r)
c := dot3(dx, dy, -g.c0.r, dx, dy, g.c0.r)
if g.a == 0 {
if b == 0 {
return color.Transparent
}
t := 0.5 * c / b
if t*g.cd.r >= g.mindr {
return getColor(t, g.stops)
}
return color.Transparent
}
discr := dot3(b, g.a, 0, b, -c, 0)
if discr >= 0 {
sqrtdiscr := math.Sqrt(discr)
t0 := (b + sqrtdiscr) * g.inva
t1 := (b - sqrtdiscr) * g.inva
if t0*g.cd.r >= g.mindr {
return getColor(t0, g.stops)
} else if t1*g.cd.r >= g.mindr {
return getColor(t1, g.stops)
}
}
return color.Transparent
}
func (g *radialGradient) AddColorStop(offset float64, color color.Color) {
g.stops = append(g.stops, stop{pos: offset, color: color})
sort.Sort(g.stops)
}
func NewRadialGradient(x0, y0, r0, x1, y1, r1 float64) Gradient {
c0 := circle{x0, y0, r0}
c1 := circle{x1, y1, r1}
cd := circle{x1 - x0, y1 - y0, r1 - r0}
a := dot3(cd.x, cd.y, -cd.r, cd.x, cd.y, cd.r)
var inva float64
if a != 0 {
inva = 1.0 / a
}
mindr := -c0.r
g := &radialGradient{
c0: c0,
c1: c1,
cd: cd,
a: a,
inva: inva,
mindr: mindr,
}
return g
}
func getColor(pos float64, stops stops) color.Color {
if pos <= 0.0 || len(stops) == 1 {
return stops[0].color
}
last := stops[len(stops)-1]
if pos >= last.pos {
return last.color
}
for i, stop := range stops[1:] {
if pos < stop.pos {
pos = (pos - stops[i].pos) / (stop.pos - stops[i].pos)
return colorLerp(stops[i].color, stop.color, pos)
}
}
return last.color
}
func colorLerp(c0, c1 color.Color, t float64) color.Color {
r0, g0, b0, a0 := c0.RGBA()
r1, g1, b1, a1 := c1.RGBA()
return color.RGBA{
lerp(r0, r1, t),
lerp(g0, g1, t),
lerp(b0, b1, t),
lerp(a0, a1, t),
}
}
func lerp(a, b uint32, t float64) uint8 {
return uint8(int32(float64(a)*(1.0-t)+float64(b)*t) >> 8)
}