GO 图像操作-遮罩

Go 图像操作-遮罩

GO 1.20 以下两种常用遮罩，用于绘制圆形与圆角矩形

package img

import (
	"image"
	"image/color"
)

// CircleMask 圆形遮罩
type CircleMask struct {
	Radius int
}

func (c CircleMask) ColorModel() color.Model {
	return color.AlphaModel
}

func (c CircleMask) Bounds() image.Rectangle {
	return image.Rect(0, 0, c.Radius*2, c.Radius*2)
}

func (c CircleMask) At(x, y int) color.Color {
	var xx, yy, r = x - c.Radius, y - c.Radius, c.Radius
	if xx*xx+yy*yy < r*r {
		return color.Alpha{A: 0xFF}
	}
	return color.Transparent
}

// RoundedRectMask 圆角矩形遮罩
type RoundedRectMask struct {
	End    image.Point
	Radius int
}

func (r RoundedRectMask) ColorModel() color.Model {
	return color.AlphaModel
}

func (r RoundedRectMask) Bounds() image.Rectangle {
	return image.Rect(0, 0, r.End.X, r.End.Y)
}

func (r RoundedRectMask) At(x, y int) color.Color {
	var xx, yy int
	rr := r.Radius
	inArea := false
	if x < rr && y < rr {
		xx, yy = x-rr, y-rr
		inArea = true
	}
	if x > r.End.X-rr && y < rr {
		xx, yy = x-r.End.X+rr, y-rr
		inArea = true
	}
	if x < rr && y > r.End.Y-rr {
		xx, yy = x-rr, y-r.End.Y+rr
		inArea = true
	}
	if x > r.End.X-rr && y > r.End.Y-rr {
		xx, yy = x-r.End.X+rr, y-r.End.Y+rr
		inArea = true
	}
	if inArea && xx*xx+yy*yy > rr*rr {
		return color.Transparent
	}
	return color.Alpha{A: 0xFF}
}

使用例

func main() {
	dest := image.NewRGBA(image.Rect(0, 0, 500, 500))

	//圆形图案
	draw.DrawMask(dest, dest.Bounds(), image.NewUniform(color.Black), image.Pt(0, 0),
		img.CircleMask{Radius: 250}, image.Pt(0, 0), draw.Over)
	//圆角图案
	draw.DrawMask(dest, dest.Bounds(), image.NewUniform(color.White), image.Pt(0, 0),
		img.RoundedRectMask{End: image.Pt(250, 250), Radius: 30}, image.Pt(-125, -125), draw.Over)

	//Output
	file, _ := os.Create("dest.png")
	_ = png.Encode(file, dest)
}

输出结果

dest.png