ios - 在图像上快速绘制图像资产

Question

我正在尝试在 Swift 4 中将名为 GreyCircle（小灰色圆圈，25x25）的图像资产绘制到图像上，但我似乎无法正确处理。顺便说一句，这是在一个点击手势功能中，也就是说，我正在尝试绘制用户点击照片的灰色圆圈。displayedImage保存当前正在显示的图像。

代码：

self.touchPoint = gestureRecognizer.location(in: self.view)
let greyCircle = UIImage(named: "GreyCircle")   

UIGraphicsBeginImageContextWithOptions(displayedImage.size, false, 0.0)
displayedImage.draw(in: CGRect(x:0, y:0, width:displayedImage.size.width, height: displayedImage.size.height))
greyCircle.draw(in: CGRect(x:touchPoint.x, y:touchPoint.y, width:displayedImage.size.width, height: displayedImage.size.height))
let newImag = UIGraphicsGetImageFromCurrentImageContext()

UIGraphicsEndImageContext()
displayedImage = newImag

该greyCircle.draw行不正确，但这是我的最新尝试。我确定我错过了一些愚蠢的东西。

标签： iosswiftuigraphicscontext

Answer 1

您想将触摸点转换为图像视图的边界。然后在绘制圆圈时，使用圆圈的大小，而不是图像的大小。

let touchPoint = gestureRecognizer.location(in: displayedImage)
let greyCircle = UIImage(named: "GreyCircle")   

UIGraphicsBeginImageContextWithOptions(displayedImage.size, false, 0.0)
displayedImage.draw(in: CGRect(x:0, y:0, width:displayedImage.size.width, height: displayedImage.size.height))
greyCircle.draw(in: CGRect(x:touchPoint.x, y:touchPoint.y, width: greyCircle.size.width, height: greyCircle.size.height))
let newImag = UIGraphicsGetImageFromCurrentImageContext()

UIGraphicsEndImageContext()
displayedImage = newImag