macos 在 OSX 上，如何渐变填充路径笔划？
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On OSX, how do I gradient fill a path stroke?
提问by Emiel
Using the plethora of drawing functions in Cocoa or Quartz it's rather easy to draw paths, and fill them using a gradient. I can't seem to find an acceptable way however, to 'stroke'-draw a path with a line width of a few pixels and fill this stroke using a gradient. How is this done?
使用 Cocoa 或 Quartz 中的大量绘图函数可以很容易地绘制路径，并使用渐变填充它们。然而，我似乎无法找到一种可接受的方法来“描边”-绘制一条线宽为几个像素的路径并使用渐变填充此描边。这是怎么做的？
Edit: Apparently the question wasn't clear enough. Thanks for the responses so far, but I already figured that out. What I want to do is this:
编辑：显然这个问题还不够清楚。感谢您到目前为止的答复，但我已经想通了。我想做的是这样的：
(source: emle.nl)
（来源：emle.nl）
The left square is NSGradient drawn in a path followed by a path stroke message. The right is what I want to do; I want to fill the stroke using the gradient.
左边的方块是在路径中绘制的 NSGradient，后跟路径笔画消息。正确的是我想做的；我想使用渐变填充笔划。
回答by Rob Keniger
If you convert the NSBezierPathto a CGPath, you can use the CGContextReplacePathWithStrokedPath()method to retrieve a path that is the outline of the stroked path. Graham Cox's excellent GCDrawKithas a -strokedPathcategory method on NSBezierPaththat will do this for you without needing to drop down to Core Graphics.
如果将 转换NSBezierPath为CGPath，则可以使用该CGContextReplacePathWithStrokedPath()方法检索作为描边路径轮廓的路径。Graham Cox 出色的GCDrawKit有一个-strokedPath类别方法NSBezierPath，可以为您完成此操作，而无需下拉到 Core Graphics。
Once you have the outlined path, you can fill that path with an NSGradient.
获得轮廓路径后，您可以使用NSGradient.
回答by Peter Hosey
I can't seem to find an acceptable way however, to 'stroke'-draw a path with a line width of a few pixels and fill this stroke using a gradient. How is this done?
然而，我似乎无法找到一种可接受的方法来“描边”-绘制一条线宽为几个像素的路径并使用渐变填充此描边。这是怎么做的？
[Original answer replaced with the following]
[原答案替换为以下内容]
Ah, I see. You want to apply the gradient to the stroke.
啊，我明白了。您想将渐变应用于笔划。
To do that, you use a blend mode. I explained how to do this in an answer on another question.Here's the list of steps, adapted to your goal:
为此，您可以使用混合模式。我在另一个问题的回答中解释了如何做到这一点。以下是适合您的目标的步骤列表：
- Begin a transparency layer.
- Stroke the path with any non-transparent color.
- Set the blend modeto source in.
- Draw the gradient.
- End the transparency layer.
回答by Bartosz Olszanowski
According to Peter Hosey's answer I've managed to do a simple gradient curve, which looks like this:
根据 Peter Hosey 的回答，我设法制作了一个简单的渐变曲线，如下所示：
I've done this in drawRect(_:) method of UIView class by writing the code below:
我通过编写以下代码在 UIView 类的 drawRect(_:) 方法中完成了此操作：
override func drawRect(rect: CGRect) {
let context = UIGraphicsGetCurrentContext()
CGContextBeginTransparencyLayer (context, nil)
let path = createCurvePath()
UIColor.blueColor().setStroke()
path.stroke()
CGContextSetBlendMode(context, .SourceIn)
let colors = [UIColor.blueColor().CGColor, UIColor.redColor().CGColor]
let colorSpace = CGColorSpaceCreateDeviceRGB()
let colorLocations :[CGFloat] = [0.0, 1.0]
let gradient = CGGradientCreateWithColors(colorSpace, colors, colorLocations)
let startPoint = CGPoint(x: 0.0, y: rect.size.height / 2)
let endPoint = CGPoint(x: rect.size.width, y: rect.size.height / 2)
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, CGGradientDrawingOptions.DrawsBeforeStartLocation)
CGContextEndTransparencyLayer(context)
}
Function createCurvePath() returns an UIBezierPath object. I've also set path.lineWidth to 5 points.
函数 createCurvePath() 返回一个 UIBezierPath 对象。我还将 path.lineWidth 设置为 5 点。
