UIView拼接UIImage，返回UIImage

如果想将多张图片、UIView拼接到一起，并返回UIImage，今天我们举例UIView，拼接UIImage，并生成UIImage。可以这样做：

首先，画UIView：

    let vVIew =UIView(frame:CGRect(x:0, y:0, width:SCREEN_width, height:SCREEN_HEIGHT-hHeight))

    vVIew.backgroundColor = UIColor.white

    let iImageLogo =UIImageView(frame: .zero)

    iImageLogo.frame=CGRect(x:0, y:0, width:120, height:40)

    iImageLogo.center= vVIew.center

    iImageLogo.image=UIImage(named:"logo")

    vVIew.addSubview(iImageLogo)

将UIIView转成UIIamge

letvVIewSize =CGSize(width:SCREEN_width, height:SCREEN_HEIGHT-hHeight)

UIGraphicsBeginImageContextWithOptions(vVIewSize,false,0.0)

vVIew.layer.render(in: UIGraphicsGetCurrentContext()!)

let bottomImage = UIGraphicsGetImageFromCurrentImageContext()

UIGraphicsEndImageContext()

多张UIImage拼接

let size =CGSize(width:SCREEN_width, height:SCREEN_HEIGHT)

UIGraphicsBeginImageContextWithOptions(size,false,0.0)

let iImageRect =CGRect(x:0, y:0, width:SCREEN_width, height: hHeight)

iImage.draw(in: iImageRect)

let vViewRect =CGRect(x:0, y:hHeight, width:SCREEN_width, height:SCREEN_HEIGHT- hHeight)

bottomImage?.draw(in: vViewRect)

let imageC = UIGraphicsGetImageFromCurrentImageContext()

 UIGraphicsEndImageContext()

这里补充说明，特别解释下UIGraphicsBeginImageContextWithOptions后面的参数：

    第一个是画板要画的大小；

    第二个参数是opaque用来决定透明通道是否被渲染，对没有透明度的图片设置这个参数为false；

    第三个参数是scale是显示缩放系数。当设置成0.0，主屏幕的缩放系数将被使用，对视网膜屏显示是2.0或者更高。