func getWaterMark(_ originalImage: UIImage?, title: String, andMark markFont: UIFont, andMark markColor: UIColor) -> UIImage? {
let HORIZONTAL_SPACE: CGFloat = 30
let VERTICAL_SPACE: CGFloat = 50
var font: UIFont? = markFont
if font == nil {
font = UIFont.systemFont(ofSize: 23)
}
var color: UIColor? = markColor
if color == nil {
color = UIColor.blue
}
//原始image的宽高
guard let viewWidth = originalImage?.size.width, let viewHeight = originalImage?.size.height else { return nil }
//为了防止图片失真,绘制区域宽高和原始图片宽高一样
UIGraphicsBeginImageContext(CGSize(width: viewWidth, height: viewHeight))
//先将原始image绘制上
originalImage?.draw(in: CGRect(x: 0, y: 0, width: viewWidth, height: viewHeight))
//sqrtLength:原始image的对角线length。在水印旋转矩阵中只要矩阵的宽高是原始image的对角线长度,无论旋转多少度都不会有空白。
let sqrtLength = sqrt(viewWidth * viewWidth + viewHeight * viewHeight)
let attrStr = NSAttributedString(string: title, attributes: [NSAttributedString.Key.foregroundColor : markColor, NSAttributedString.Key.font: markFont])
//绘制文字的宽高
let strWidth = attrStr.size().width
let strHeight = attrStr.size().height
//开始旋转上下文矩阵,绘制水印文字
let context = UIGraphicsGetCurrentContext()
//将绘制原点(0,0)调整到源image的中心
context?.concatenate(CGAffineTransform(translationX: viewWidth / 2, y: viewHeight / 2))
//以绘制原点为中心旋转
context?.concatenate(CGAffineTransform(rotationAngle: CGFloat(M_PI_2 / 3)))
//将绘制原点恢复初始值,保证当前context中心和源image的中心处在一个点(当前context已经旋转,所以绘制出的任何layer都是倾斜的)
context?.concatenate(CGAffineTransform(translationX: -viewWidth / 2, y: -viewHeight / 2))
//计算需要绘制的列数和行数
let horCount: Int = Int(sqrtLength / CGFloat(strWidth + HORIZONTAL_SPACE)) + 1
let verCount: Int = Int(sqrtLength / CGFloat(strHeight + VERTICAL_SPACE)) + 1
//此处计算出需要绘制水印文字的起始点,由于水印区域要大于图片区域所以起点在原有基础上移
let orignX: CGFloat = -(sqrtLength - viewWidth) / 2
let orignY: CGFloat = -(sqrtLength - viewHeight) / 2
//在每列绘制时X坐标叠加
var tempOrignX: CGFloat = orignX
//在每行绘制时Y坐标叠加
var tempOrignY: CGFloat = orignY
for i in 0..<horCount * verCount {
title.draw(in: CGRect(x: tempOrignX, y: tempOrignY, width: strWidth, height: strHeight), withAttributes: [NSAttributedString.Key.foregroundColor : markColor, NSAttributedString.Key.font: markFont])
if i % horCount == 0 && i != 0 {
tempOrignX = orignX
tempOrignY += strHeight + VERTICAL_SPACE
} else {
tempOrignX += strWidth + HORIZONTAL_SPACE
}
}
//根据上下文制作成图片
let finalImg: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return finalImg
}
效果图
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