Added striped patterns

artist/chisel.go

@@ -10,14 +10,9 @@ type Chiseled struct {
 
 // AtWhen satisfies the Pattern interface.
 func (chiseled Chiseled) AtWhen (x, y, width, height int) (c color.RGBA) {
-	var highlighted bool
-	// FIXME: this doesn't work quite right, the
-	// slope of the line is somewhat off.
-	// bottomCorner :=
-		// float64(x) < float64(y) *
-		// (float64(width) / float64(height))
-	bottomCorner := false
-
+	var highlighted  bool
+	var bottomCorner bool
+	
 	if width > height {
 		bottomCorner = y > height / 2
 	} else {

artist/striped.go

@@ -0,0 +1,47 @@
+package artist
+
+import "image/color"
+
+// StripeDirection specifies the direction of stripes.
+type StripeDirection int
+
+const (
+	StripeDirectionVertical StripeDirection = iota
+	StripeDirectionDiagonalRight
+	StripeDirectionHorizontal
+	StripeDirectionDiagonalLeft
+)
+
+// Striped is a pattern that produces stripes of two alternating colors.
+type Striped struct {
+	First     Pattern
+	Second    Pattern
+	Direction StripeDirection
+	Weight    int
+}
+
+// AtWhen satisfies the Pattern interface.
+func (pattern Striped) AtWhen (x, y, width, height int) (c color.RGBA) {
+	position := 0
+	switch pattern.Direction {
+	case StripeDirectionVertical:
+		position = x
+	case StripeDirectionDiagonalRight:
+		position = x + y
+	case StripeDirectionHorizontal:
+		position = y
+	case StripeDirectionDiagonalLeft:
+		position = x - y
+	}
+
+	position %= pattern.Weight * 2
+	if position < 0 {
+		position += pattern.Weight * 2
+	}
+	
+	if position < pattern.Weight {
+		return pattern.First.AtWhen(x, y, width, height)
+	} else {
+		return pattern.Second.AtWhen(x, y, width, height)
+	}
+}