英文:
Golang how do you crop a circular image out of a rectangular jpeg.
问题
在Golang中，如何从矩形的jpeg图像中裁剪出一个圆形图像。矩形的大小可能会有所变化。如果你有一个image.Image对象，你可以如何从图像的中心裁剪出一个尽可能占据空间的圆形？我想保留圆形部分并移除其他部分。
英文:
In Golang how do you crop a circular image out of a rectangular jpeg. The rectangle can vary in size. If you have an image.Image would you crop out a circle from the center of the image where the circle takes up as much space as possible? I want to keep the circle and remove the rest.
答案1
得分: 7
这个例子使用了来自golang博客的绘图包，大致可以满足你的需求；
type circle struct {
p image.Point
r int
}
func (c *circle) ColorModel() color.Model {
return color.AlphaModel
}
func (c *circle) Bounds() image.Rectangle {
return image.Rect(c.p.X-c.r, c.p.Y-c.r, c.p.X+c.r, c.p.Y+c.r)
}
func (c *circle) At(x, y int) color.Color {
xx, yy, rr := float64(x-c.p.X)+0.5, float64(y-c.p.Y)+0.5, float64(c.r)
if xx*xx+yy*yy < rr*rr {
return color.Alpha{255}
}
return color.Alpha{0}
}
draw.DrawMask(dst, dst.Bounds(), src, image.ZP, &circle{p, r}, image.ZP, draw.Over)
请注意，它接受一个矩形，并使用以点p为起点、半径为r的圆形遮罩除了圆形之外的所有内容。完整的文章可以在这里找到：http://blog.golang.org/go-imagedraw-package
在你的情况下，你希望遮罩只是你的普通背景，而源图像是你想要使用部分的矩形图像。
英文:
This example using the drawing package from the golang blog should do roughly what you want;
type circle struct {
p image.Point
r int
}
func (c *circle) ColorModel() color.Model {
return color.AlphaModel
}
func (c *circle) Bounds() image.Rectangle {
return image.Rect(c.p.X-c.r, c.p.Y-c.r, c.p.X+c.r, c.p.Y+c.r)
}
func (c *circle) At(x, y int) color.Color {
xx, yy, rr := float64(x-c.p.X)+0.5, float64(y-c.p.Y)+0.5, float64(c.r)
if xx*xx+yy*yy < rr*rr {
return color.Alpha{255}
}
return color.Alpha{0}
}
draw.DrawMask(dst, dst.Bounds(), src, image.ZP, &circle{p, r}, image.ZP, draw.Over)
Note that it takes a rectangle and masks everything but the circle beginning at point p with radius r. The full article can be found here http://blog.golang.org/go-imagedraw-package
In your case you would like the mask to just be your normal background and the src to be the currently rectangular image you'd like to use part of.
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