Initial commit

canvas/canvas.go

@@ -0,0 +1,96 @@
+package xcanvas
+
+import "image"
+import "image/color"
+import "github.com/jezek/xgbutil"
+import "git.tebibyte.media/tomo/ggfx"
+import "github.com/jezek/xgbutil/xgraphics"
+import "git.tebibyte.media/tomo/tomo/canvas"
+
+// Canvas satisfies the canvas.Canvas interface. It draws to an xgraphics.Image.
+type Canvas struct {
+	*xgraphics.Image
+}
+
+// New creates a new canvas from a bounding rectangle.
+func New (x *xgbutil.XUtil, bounds image.Rectangle) Canvas {
+	return Canvas { xgraphics.New(x, bounds) }
+}
+
+// NewFrom creates a new canvas from an existing xgraphics.Image.
+func NewFrom (image *xgraphics.Image) Canvas {
+	return Canvas { image }
+}
+
+// Pen returns a new drawing context.
+func (this Canvas) Pen () canvas.Pen {
+	return pen {
+		image: this.Image,
+		gfx:   ggfx.Image[uint8] {
+			Pix:    this.Image.Pix,
+			Stride: this.Image.Stride,
+			Bounds: this.Image.Rect,
+			Width: 4,
+		},
+	}
+}
+
+// Clip returns a sub-canvas of this canvas.
+func (this Canvas) Clip (bounds image.Rectangle) Canvas {
+	return Canvas { this.Image.SubImage(bounds).(*xgraphics.Image) }
+}
+
+// TODO: we need to implement:
+//  - cap
+//  - joint
+//  - align
+
+type pen struct {
+	image *xgraphics.Image
+	gfx    ggfx.Image[uint8]
+
+	closed bool
+	endCap canvas.Cap
+	joint  canvas.Joint
+	weight int
+	align  canvas.StrokeAlign
+	stroke [4]uint8
+	fill   [4]uint8
+}
+
+func (this pen) Rectangle (bounds image.Rectangle) {
+	if this.weight == 0 {
+		this.gfx.FillRectangle(this.fill[:], bounds)
+	} else {
+		this.gfx.StrokeRectangle(this.stroke[:], this.weight, bounds)
+	}
+}
+
+func (this pen) Path (points ...image.Point) {
+	if this.weight == 0 {
+		this.gfx.FillPolygon(this.fill[:], points...)
+	} else if this.closed {
+		this.gfx.StrokePolygon(this.stroke[:], this.weight, points...)
+	} else {
+		this.gfx.PolyLine(this.stroke[:], this.weight, points...)
+	}
+}
+ 
+func (this pen) Closed       (closed bool)              { this.closed = closed }
+func (this pen) Cap          (endCap canvas.Cap)        { this.endCap = endCap }
+func (this pen) Joint        (joint  canvas.Joint)      { this.joint  = joint  }
+func (this pen) StrokeWeight (weight int)               { this.weight = weight }
+func (this pen) StrokeAlign  (align canvas.StrokeAlign) { this.align  = align  }
+
+func (this pen) Stroke (stroke color.Color) { this.stroke = convertColor(stroke) }
+func (this pen) Fill (fill color.Color)     { this.fill   = convertColor(fill)   }
+
+func convertColor (c color.Color) [4]uint8 {
+	r, g, b, a := c.RGBA()
+	return [4]uint8 {
+		uint8(b >> 8),
+		uint8(g >> 8),
+		uint8(a >> 8),
+		uint8(r >> 8),
+	}
+}