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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package vector_test
import (
"image"
"image/draw"
"os"
"golang.org/x/image/vector"
)
func Example_draw() {
const (
width = 30
height = 20
)
// Define a closed shape with three edges: two linear and one quadratic.
// One of its vertices is at the top-left corner of the (1, 2) pixel, which
// is also the bottom-right corner of the (0, 1) pixel.
//
// Co-ordinates can be floating point numbers, not just integers. They can
// also be outside the vector.Rasterizer's dimensions. The shapes will be
// clipped during rasterization.
r := vector.NewRasterizer(width, height)
r.DrawOp = draw.Src
r.MoveTo(1, 2)
r.LineTo(20, 2)
r.QuadTo(40.5, 15, 10, 20)
r.ClosePath()
// Finish the rasterization: the conversion from vector graphics (shapes)
// to raster graphics (pixels). Co-ordinates are now integers.
dst := image.NewAlpha(image.Rect(0, 0, width, height))
r.Draw(dst, dst.Bounds(), image.Opaque, image.Point{})
// Visualize the pixels.
const asciiArt = ".++8"
buf := make([]byte, 0, height*(width+1))
for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
a := dst.AlphaAt(x, y).A
buf = append(buf, asciiArt[a>>6])
}
buf = append(buf, '\n')
}
os.Stdout.Write(buf)
// Output:
// ..............................
// ..............................
// .8888888888888888888+.........
// .+88888888888888888888+.......
// ..888888888888888888888+......
// ..+888888888888888888888+.....
// ...8888888888888888888888+....
// ...+8888888888888888888888+...
// ....88888888888888888888888+..
// ....+88888888888888888888888..
// .....88888888888888888888888..
// .....+8888888888888888888888..
// ......8888888888888888888888..
// ......+88888888888888888888+..
// .......8888888888888888888+...
// .......+88888888888888888.....
// ........888888888888888+......
// ........+88888888888+.........
// .........8888888++............
// .........+8+++................
}
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