如何在 swift 编程中在 UIimage 中设置背景颜色

Question

I draw an image using drawInRect() method.

My rectangle is size of 120*120 and my image is 100 * 100.

How i can set a background color to my image in swift?

Answer 1

Swift 5, 4

If you need to draw the background of an image, for optimization and decorative purposes, you can draw the image in a specific way:

UIImage(named: "someImage")?.withBackground(color: .white)

---

Extension

extension UIImage {
  func withBackground(color: UIColor, opaque: Bool = true) -> UIImage {
    UIGraphicsBeginImageContextWithOptions(size, opaque, scale)
        
    guard let ctx = UIGraphicsGetCurrentContext(), let image = cgImage else { return self }
    defer { UIGraphicsEndImageContext() }
        
    let rect = CGRect(origin: .zero, size: size)
    ctx.setFillColor(color.cgColor)
    ctx.fill(rect)
    ctx.concatenate(CGAffineTransform(a: 1, b: 0, c: 0, d: -1, tx: 0, ty: size.height))
    ctx.draw(image, in: rect)
        
    return UIGraphicsGetImageFromCurrentImageContext() ?? self
  }
}

Answer 2

You can also use this extension:

    extension UIImage {
        func imageWithColor(tintColor: UIColor) -> UIImage {
            UIGraphicsBeginImageContextWithOptions(self.size, false, self.scale)

            let context = UIGraphicsGetCurrentContext()!
            context.translateBy(x: 0, y: self.size.height)
            context.scaleBy(x: 1.0, y: -1.0);
            context.setBlendMode(.normal)

            let rect = CGRect(x: 0, y: 0, width: self.size.width, height: self.size.height) as CGRect
            context.clip(to: rect, mask: self.cgImage!)
            tintColor.setFill()
            context.fill(rect)

            let newImage = UIGraphicsGetImageFromCurrentImageContext()!
            UIGraphicsEndImageContext()

            return newImage
        }
    }

And then

image.imageWithColor("#1A6BAE".UIColor)

EDIT: 2019-11: Updated to Swift 5 by @Yuto

Answer 3

Updated @Egghead's solution for Swift 3

extension UIImage {
   static func imageWithColor(tintColor: UIColor) -> UIImage {
        let rect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContextWithOptions(rect.size, false, 0)
        tintColor.setFill()
        UIRectFill(rect)
        let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return image
    }
}

Usage :

UIImage.imageWithColor(tintColor: <Custom color>)

Answer 4

It's probably best to use the backgroundColor property of your UIImageView. You can do this as follows -

self.imageView.backgroundColor = UIColor.redColor()

The following preset colors exist:

blackColor
darkGrayColor
lightGrayColor
whiteColor
grayColor
redColor
greenColor
blueColor
cyanColor
yellowColor
magentaColor
orangeColor
purpleColor
brownColor
clearColor

If you instead want to programmatically create a UIImage with a given color, you can do this as follows:

var rect = CGRectMake(0, 0, size.width, size.height)
UIGraphicsBeginImageContextWithOptions(size, false, 0)
color.setFill()
UIRectFill(rect)
var image: UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

Where the var 'image' is your colored UIImage.

Answer 5

An other way to obtain an image with a background color with an extension is: (Swift 3)

extension UIImage {

    /**
        Returns an UIImage with a specified background color.
        - parameter color: The color of the background
     */
    convenience init(withBackground color: UIColor) {

        let rect: CGRect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContext(rect.size);
        let context:CGContext = UIGraphicsGetCurrentContext()!;
        context.setFillColor(color.cgColor);
        context.fill(rect)

        let image:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()

        self.init(ciImage: CIImage(image: image)!)

    }
}

And then:

// change UIColor.white with your color
let image = UIImage(withBackground: UIColor.white)

Answer 6

Solution for swift 4 based on the already acepted answer:

func imageWithColor(tintColor: UIColor) -> UIImage {
    UIGraphicsBeginImageContextWithOptions(self.size, false, self.scale)

    let context = UIGraphicsGetCurrentContext() as! CGContext
    context.translateBy(x: 0, y: size.height)
    context.scaleBy(x: 1, y: -1)
    context.setBlendMode(.normal)

    let rect = CGRect(x: 0, y: 0, width: self.size.width, height: self.size.height) as CGRect
    context.clip(to: rect, mask: self.cgImage!)
    tintColor.setFill()
    context.fill(rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext() as! UIImage
    UIGraphicsEndImageContext()

    return newImage
}

Usage:

image.imageWithColor("#1A6BAE".UIColor)