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tomo-old/canvas/canvas.go

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package canvas
import "image"
import "image/draw"
import "image/color"
// Image represents an immutable canvas.
type Image interface {
image.Image
RGBAAt (x, y int) color.RGBA
}
// 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
}