Atomized the functionality of the base tomo package

canvas/canvas.go

@@ -0,0 +1,90 @@
+package canvas
+
+import "image"
+import "image/draw"
+import "image/color"
+
+// Canvas is like draw.Image but is also able to return a raw pixel buffer for
+// more efficient drawing. This interface can be easily satisfied using a
+// BasicCanvas struct.
+type Canvas interface {
+	draw.Image
+	Buffer () (data []color.RGBA, stride int)
+}
+
+// BasicCanvas is a general purpose implementation of tomo.Canvas.
+type BasicCanvas struct {
+	pix    []color.RGBA
+	stride int
+	rect   image.Rectangle
+}
+
+// NewBasicCanvas creates a new basic canvas with the specified width and
+// height, allocating a buffer for it.
+func NewBasicCanvas (width, height int) (canvas BasicCanvas) {
+	canvas.pix    = make([]color.RGBA, height * width)
+	canvas.stride = width
+	canvas.rect = image.Rect(0, 0, width, height)
+	return
+}
+
+// you know what it do
+func (canvas BasicCanvas) Bounds () (bounds image.Rectangle) {
+	return canvas.rect
+}
+
+// you know what it do
+func (canvas BasicCanvas) At (x, y int) (color.Color) {
+	if !image.Pt(x, y).In(canvas.rect) { return nil }
+	return canvas.pix[x + y * canvas.stride]
+}
+
+// you know what it do
+func (canvas BasicCanvas) ColorModel () (model color.Model) {
+	return color.RGBAModel
+}
+
+// you know what it do
+func (canvas BasicCanvas) Set (x, y int, c color.Color) {
+	if !image.Pt(x, y).In(canvas.rect) { return }
+	r, g, b, a := c.RGBA()
+	canvas.pix[x + y * canvas.stride] = color.RGBA {
+		R: uint8(r >> 8),
+		G: uint8(g >> 8),
+		B: uint8(b >> 8),
+		A: uint8(a >> 8),
+	}
+}
+
+// you know what it do
+func (canvas BasicCanvas) Buffer () (data []color.RGBA, stride int) {
+	return canvas.pix, canvas.stride
+}
+
+// Reallocate efficiently reallocates the canvas. The data within will be
+// garbage. This method will do nothing if this is a cut image.
+func (canvas *BasicCanvas) Reallocate (width, height int) {
+	if canvas.rect.Min != (image.Point { }) { return }
+
+	previousLen := len(canvas.pix)
+	newLen := width * height
+	bigger  := newLen > previousLen
+	smaller := newLen < previousLen / 2
+	if bigger || smaller {
+		canvas.pix = make (
+			[]color.RGBA,
+			((height * width) / 4096) * 4096 + 4096)
+	}
+	canvas.stride = width
+	canvas.rect = image.Rect(0, 0, width, height)
+}
+
+// Cut returns a sub-canvas of a given canvas.
+func Cut (canvas Canvas, bounds image.Rectangle) (reduced BasicCanvas) {
+	// println(canvas.Bounds().String(), bounds.String())
+	bounds = bounds.Intersect(canvas.Bounds())
+	if bounds.Empty() { return }
+	reduced.rect = bounds
+	reduced.pix, reduced.stride = canvas.Buffer()
+	return
+}