vector: add example test
Fixes golang/go#45723
Change-Id: Id9131dd690a4496ed5ec8aae3bf4d54f44a53d79
Reviewed-on: https://go-review.googlesource.com/c/image/+/316069
Trust: Nigel Tao <nigeltao@golang.org>
Run-TryBot: Nigel Tao <nigeltao@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/font/sfnt/example_test.go b/font/sfnt/example_test.go
index 3e40a71..c023d1e 100644
--- a/font/sfnt/example_test.go
+++ b/font/sfnt/example_test.go
@@ -25,6 +25,7 @@
originY = 32
)
+ // Load the 'G' glyph from the Go Regular font.
f, err := sfnt.Parse(goregular.TTF)
if err != nil {
log.Fatalf("Parse: %v", err)
@@ -42,6 +43,7 @@
log.Fatalf("LoadGlyph: %v", err)
}
+ // Translate and scale that glyph as we pass it to a vector.Rasterizer.
r := vector.NewRasterizer(width, height)
r.DrawOp = draw.Src
for _, seg := range segments {
@@ -77,9 +79,12 @@
}
}
+ // Finish the rasterization: the conversion from vector graphics (shapes)
+ // to raster graphics (pixels).
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++ {
diff --git a/vector/example_test.go b/vector/example_test.go
new file mode 100644
index 0000000..859b6c4
--- /dev/null
+++ b/vector/example_test.go
@@ -0,0 +1,73 @@
+// 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+++................
+}
