用对角线绘制线条填充UIView？

Question

如何填充像这样的UIView（用一些对角线绘制的白线）。

PS：我的意图是填补而不是边界。

有帮助吗？

Answer 1

实现这一目标的一种方法是覆盖draw(_:)的UIView方法并在那里进行自定义绘制。

绘制对角线非常简单，您只需要：

• 从0到宽度+高度（沿着矩形的水平边缘，然后向上），通过间隙+线宽，从对角线（45º）长度转换为平行于绘制的矩形边缘在。
• 在每次迭代时，从该迭代的给定点绘制一条直线到相对边缘上的点（45°）。我们通过简单地处理矩形的垂直边缘然后沿着水平方向得到这一点。

这样的事情应该达到预期的效果：

class StripeyView : UIView {

    let lineGap: CGFloat = 7
    let lineWidth: CGFloat = 3
    let lineColor = UIColor.white

    override func draw(_ rect: CGRect) {

        let ctx = UIGraphicsGetCurrentContext()!

        // flip y-axis of context, so (0,0) is the bottom left of the context
        ctx.scaleBy(x: 1, y: -1)
        ctx.translateBy(x: 0, y: -bounds.size.height)

        // generate a slightly larger rect than the view,
        // to allow the lines to appear seamless
        let renderRect = bounds.insetBy(dx: -lineWidth * 0.5, dy: -lineWidth * 0.5)

        // the total distance to travel when looping (each line starts at a point that
        // starts at (0,0) and ends up at (width, height)).
        let totalDistance = renderRect.size.width + renderRect.size.height

        // loop through distances in the range 0 ... totalDistance
        for distance in stride(from: 0, through: totalDistance,
                               // divide by cos(45º) to convert from diagonal length
                               by: (lineGap + lineWidth) / cos(.pi / 4)) {

            // the start of one of the stripes
            ctx.move(to: CGPoint(
                // x-coordinate based on whether the distance is less than the width of the
                // rect (it should be fixed if it is above, and moving if it is below)
                x: distance < renderRect.width ?
                    renderRect.origin.x + distance :
                    renderRect.origin.x + renderRect.width,

                // y-coordinate based on whether the distance is less than the width of the
                // rect (it should be moving if it is above, and fixed if below)
                y: distance < renderRect.width ?
                    renderRect.origin.y :
                    distance - (renderRect.width - renderRect.origin.x)
            ))

            // the end of one of the stripes
            ctx.addLine(to: CGPoint(
                // x-coordinate based on whether the distance is less than the height of
                // the rect (it should be moving if it is above, and fixed if it is below)
                x: distance < renderRect.height ?
                    renderRect.origin.x :
                    distance - (renderRect.height - renderRect.origin.y),

                // y-coordinate based on whether the distance is less than the height of
                // the rect (it should be fixed if it is above, and moving if it is below)
                y: distance < renderRect.height ?
                    renderRect.origin.y + distance :
                    renderRect.origin.y + renderRect.height
            ))
        }

        // stroke all of the lines added
        ctx.setStrokeColor(lineColor.cgColor)
        ctx.setLineWidth(lineWidth)
        ctx.strokePath()
    }
}

输出：

（假设视图有红色backgroundColor）

您可以调整lineGap和lineWidth属性以生成不同的结果。

Answer 2

Amazingly simple algorithm ...

说你有这些价值观：

    let T: CGFloat = 15     // desired thickness of lines
    let G: CGFloat = 30     // desired gap between lines
    let W = rect.size.width
    let H = rect.size.height

值得注意的是，就是这么简单......

    var p = -(W > H ? W : H) - T
    while p <= W {

        c.move( to: CGPoint(x: p-T, y: -T) )
        c.addLine( to: CGPoint(x: p+T+H, y: T+H) )
        c.strokePath()
        p += G + T + T
    }

这是一个完整的UIView类：

class Ruled: UIView {

    override func draw(_ rect: CGRect) {

        let T: CGFloat = 15     // desired thickness of lines
        let G: CGFloat = 30     // desired gap between lines
        let W = rect.size.width
        let H = rect.size.height

        guard let c = UIGraphicsGetCurrentContext() else { return }
        c.setStrokeColor(UIColor.orange.cgColor)
        c.setLineWidth(T)

        var p = -(W > H ? W : H) - T
        while p <= W {

            c.move( to: CGPoint(x: p-T, y: -T) )
            c.addLine( to: CGPoint(x: p+T+H, y: T+H) )
            c.strokePath()
            p += G + T + T
        }
    }
}

而已 ！

整个基本算法：

1. Start at the top-left, minus the longest side

2. Draw diagonals until you come to the right

好，易于！ :)

---

To clip to a rectangle:

上面的类只是绘制一个大小与UIView相同的“盒子”。

通常，您希望在一个视图中，在不同位置绘制许多“框”。一个典型的例子是日历。

此示例将绘制一个框。为您需要绘制的每个方框调用它：

此外，此示例显式绘制两个条纹，而不是在背景颜色上绘制一个条纹：

func simpleStripes(x: CGFloat, y: CGFloat, width: CGFloat, height: CGFloat) {

    let stripeWidth: CGFloat = 20.0 // whatever you want
    let m = stripeWidth / 2.0

    guard let c = UIGraphicsGetCurrentContext() else { return }
    c.setLineWidth(stripeWidth)

    let r = CGRect(x: x, y: y, width: width, height: height)
    let longerSide = width > height ? width : height

    c.saveGState()
    c.clip(to: r)

        var p = x - longerSide
        while p <= x + width {

            c.setStrokeColor(pale blue)
            c.move( to: CGPoint(x: p-m, y: y-m) )
            c.addLine( to: CGPoint(x: p+m+height, y: y+m+height) )
            c.strokePath()

            p += stripeWidth

            c.setStrokeColor(pale gray)
            c.move( to: CGPoint(x: p-m, y: y-m) )
            c.addLine( to: CGPoint(x: p+m+height, y: y+m+height) )
            c.strokePath()

            p += stripeWidth
        }

    c.restoreGState()
}

---

If you want to animate them moving...

1，要偏移，只需在启动时从指针中减去。令人惊讶的是，没有别的东西需要改变。

  var p = x - longerSide - offset // animate offset from 0 to stripeWidth

2，细心的程序员更喜欢偏差等于斜角以避免“尖尖的左上角”问题：

  var p = x - longerSide - offset - m // for better-looking top-left corner

3，您可以使用各种颜色的任意数量的条纹，实际上您可以使用任意组合的不同条纹宽度。令人惊讶的是，该算法仍然有效且安全。 （如果您有多个宽度，只需将斜角m设置为最大宽度。）

Answer 3

绘制斜线的最简单代码：

import UIKit

@IBDesignable
class SlashPatternView: UIView {
@IBInspectable
var lineWidth: CGFloat = 1 { didSet { setNeedsLayout() } }

@IBInspectable
var squareSize: CGFloat = 1 { didSet { setNeedsLayout() } }

@IBInspectable
var lineColor: UIColor = .white { didSet { setNeedsLayout() }}

var slashes: UIImage {
    let size = squareSize
    let renderer = UIGraphicsImageRenderer(size: CGSize(width: size, height: size))
    return renderer.image { context in
        let cgcontext = context.cgContext

        cgcontext.addLines(between: [CGPoint(x: 0, y: size/2), CGPoint(x: size/2, y: 0)])
        cgcontext.addLines(between: [CGPoint(x: size/2, y: size), CGPoint(x: size, y: size/2)])

        cgcontext.setStrokeColor(lineColor.cgColor)
        cgcontext.setLineCap(.square)
        cgcontext.setLineWidth(lineWidth)
        cgcontext.strokePath()
    }
}
override func layoutSubviews() {
    super.layoutSubviews()
}


override func draw(_ rect: CGRect) {
    backgroundColor?.setFill()
    UIRectFill(rect)
    slashes.drawAsPattern(in: rect)
}
}