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