Created an elliptical border pattern

artist/circlebordered.go

@@ -0,0 +1,33 @@
+package artist
+
+import "math"
+import "image/color"
+
+// EllipticallyBordered is a pattern with a border and a fill that is elliptical
+// in shape.
+type EllipticallyBordered struct {
+	Fill Pattern
+	Stroke
+}
+
+// AtWhen satisfies the Pattern interface.
+func (pattern EllipticallyBordered) AtWhen (x, y, width, height int) (c color.RGBA) {
+	xf := (float64(x) + 0.5) / float64(width ) * 2 - 1
+	yf := (float64(y) + 0.5) / float64(height) * 2 - 1
+	distance := math.Sqrt(xf * xf + yf * yf)
+
+	var radius float64
+	if width < height {
+		// vertical
+		radius = 1 - float64(pattern.Weight * 2) / float64(width)
+	} else {
+		// horizontal
+		radius = 1 - float64(pattern.Weight * 2) / float64(height)
+	}
+
+	if distance < radius {
+		return pattern.Fill.AtWhen(x, y, width, height)
+	} else {
+		return pattern.Stroke.AtWhen(x, y, width, height)
+	}
+}

elements/testing/artist.go

@@ -20,7 +20,7 @@ type Artist struct {
 func NewArtist () (element *Artist) {
 	element = &Artist { }
 	element.Core, element.core = core.NewCore(element)
-	element.core.SetMinimumSize(400, 512)
+	element.core.SetMinimumSize(400, 600)
 	return
 }
 
@@ -28,7 +28,7 @@ func (element *Artist) Resize (width, height int) {
 	element.core.AllocateCanvas(width, height)
 	bounds := element.Bounds()
 	element.cellBounds.Max.X = bounds.Dx() / 4
-	element.cellBounds.Max.Y = (bounds.Dy() - 48) / 7
+	element.cellBounds.Max.Y = (bounds.Dy() - 48) / 8
 
 	drawStart := time.Now()
 
@@ -202,6 +202,15 @@ func (element *Artist) Resize (width, height int) {
 			},
 			element.cellAt(x, 6))
 	}
+
+	// 0, 7
+	artist.FillEllipse (
+		element,
+		artist.EllipticallyBordered {
+			Fill: uhex(0xFF0000FF),
+			Stroke: artist.Stroke { Pattern: uhex(0x00FF00), Weight: 5 },
+		},
+		element.cellAt(0, 7))
 }
 
 func (element *Artist) lines (weight int, bounds image.Rectangle) {