implemented software gradients

backend/gogl/shaders.go

@@ -244,7 +244,7 @@ void main() {
 		return;
 	}
 	float o = max(o1, o2);
-	float r = radFrom + o * (radTo - radFrom);
+	//float r = radFrom + o * (radTo - radFrom);
     vec4 col = texture2D(gradient, vec2(o, 0.0));
     col.a *= texture2D(alphaTex, v_atc).a * globalAlpha;
 	gl_FragColor = col;

backend/software/fill.go

@@ -3,6 +3,7 @@ package softwarebackend
 import (
 	"image"
 	"image/color"
+	"math"
 
 	"github.com/tfriedel6/canvas/backend/backendbase"
 )
@@ -19,23 +20,50 @@ func (b *SoftwareBackend) Clear(pts [4][2]float64) {
 }
 
 func (b *SoftwareBackend) Fill(style *backendbase.FillStyle, pts [][2]float64) {
-	p2 := b.mask.Pix
+	b.clearMask()
-	for i := range p2 {
-		p2[i] = 0
-	}
 
-	iterateTriangles(pts[:], func(tri [][2]float64) {
+	if lg := style.LinearGradient; lg != nil {
-		b.fillTriangle(tri, func(x, y int) {
+		lg := lg.(*LinearGradient)
-			if b.clip.AlphaAt(x, y).A == 0 {
+		from := [2]float64{style.Gradient.X0, style.Gradient.Y0}
+		dir := [2]float64{style.Gradient.X1 - style.Gradient.X0, style.Gradient.Y1 - style.Gradient.Y0}
+		dirlen := math.Sqrt(dir[0]*dir[0] + dir[1]*dir[1])
+		dir[0] /= dirlen
+		dir[1] /= dirlen
+		b.fillTriangles(pts, func(x, y int) {
+			pos := [2]float64{float64(x) - from[0], float64(y) - from[1]}
+			r := (pos[0]*dir[0] + pos[1]*dir[1]) / dirlen
+			color := lg.data.ColorAt(r)
+			b.Image.SetRGBA(x, y, mix(color, b.Image.RGBAAt(x, y)))
+		})
+	} else if rg := style.RadialGradient; rg != nil {
+		rg := rg.(*RadialGradient)
+		from := [2]float64{style.Gradient.X0, style.Gradient.Y0}
+		to := [2]float64{style.Gradient.X1, style.Gradient.Y1}
+		radFrom := style.Gradient.RadFrom
+		radTo := style.Gradient.RadTo
+		b.fillTriangles(pts, func(x, y int) {
+			pos := [2]float64{float64(x), float64(y)}
+			oa := 0.5 * math.Sqrt(
+				math.Pow(-2.0*from[0]*from[0]+2.0*from[0]*to[0]+2.0*from[0]*pos[0]-2.0*to[0]*pos[0]-2.0*from[1]*from[1]+2.0*from[1]*to[1]+2.0*from[1]*pos[1]-2.0*to[1]*pos[1]+2.0*radFrom*radFrom-2.0*radFrom*radTo, 2.0)-
+					4.0*(from[0]*from[0]-2.0*from[0]*pos[0]+pos[0]*pos[0]+from[1]*from[1]-2.0*from[1]*pos[1]+pos[1]*pos[1]-radFrom*radFrom)*
+						(from[0]*from[0]-2.0*from[0]*to[0]+to[0]*to[0]+from[1]*from[1]-2.0*from[1]*to[1]+to[1]*to[1]-radFrom*radFrom+2.0*radFrom*radTo-radTo*radTo))
+			ob := (from[0]*from[0] - from[0]*to[0] - from[0]*pos[0] + to[0]*pos[0] + from[1]*from[1] - from[1]*to[1] - from[1]*pos[1] + to[1]*pos[1] - radFrom*radFrom + radFrom*radTo)
+			oc := (from[0]*from[0] - 2.0*from[0]*to[0] + to[0]*to[0] + from[1]*from[1] - 2.0*from[1]*to[1] + to[1]*to[1] - radFrom*radFrom + 2.0*radFrom*radTo - radTo*radTo)
+			o1 := (-oa + ob) / oc
+			o2 := (oa + ob) / oc
+			if math.IsNaN(o1) && math.IsNaN(o2) {
 				return
 			}
-			if b.mask.AlphaAt(x, y).A > 0 {
+			o := math.Max(o1, o2)
-				return
+			col := rg.data.ColorAt(o)
-			}
+			b.Image.SetRGBA(x, y, mix(col, b.Image.RGBAAt(x, y)))
-			b.mask.SetAlpha(x, y, color.Alpha{A: 255})
+			b.Image.SetRGBA(x, y, color.RGBA{R: 255, A: 255})
+		})
+	} else {
+		b.fillTriangles(pts, func(x, y int) {
 			b.Image.SetRGBA(x, y, mix(style.Color, b.Image.RGBAAt(x, y)))
 		})
-	})
+	}
 }
 
 func (b *SoftwareBackend) FillImageMask(style *backendbase.FillStyle, mask *image.Alpha, pts [4][2]float64) {
@@ -52,6 +80,13 @@ func (b *SoftwareBackend) FillImageMask(style *backendbase.FillStyle, mask *imag
 	})
 }
 
+func (b *SoftwareBackend) clearMask() {
+	p := b.mask.Pix
+	for i := range p {
+		p[i] = 0
+	}
+}
+
 func (b *SoftwareBackend) ClearClip() {
 	p := b.clip.Pix
 	for i := range p {

backend/software/triangles.go

@@ -1,6 +1,7 @@
 package softwarebackend
 
 import (
+	"image/color"
 	"math"
 )
 
@@ -173,3 +174,18 @@ func iterateTriangles(pts [][2]float64, fn func(tri [][2]float64)) {
 		fn(pts[i-3 : i])
 	}
 }
+
+func (b *SoftwareBackend) fillTriangles(pts [][2]float64, fn func(x, y int)) {
+	iterateTriangles(pts[:], func(tri [][2]float64) {
+		b.fillTriangle(tri, func(x, y int) {
+			if b.clip.AlphaAt(x, y).A == 0 {
+				return
+			}
+			if b.mask.AlphaAt(x, y).A > 0 {
+				return
+			}
+			b.mask.SetAlpha(x, y, color.Alpha{A: 255})
+			fn(x, y)
+		})
+	})
+}