在UIImage周围添加透明空间

Question

假设我们有600X400的图像，我们希望最终得到1000X100的新图像，其中包含中心的初始图像和周围的透明空间。我怎样才能在代码中实现这一目标？

Answer 1

在Swift中，你可以为UIImage写一个扩展，用它绘制带有插图的图像。

Swift 3 ：

import UIKit

extension UIImage {
    func imageWithInsets(insets: UIEdgeInsets) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(
            CGSize(width: self.size.width + insets.left + insets.right,
                   height: self.size.height + insets.top + insets.bottom), false, self.scale)
        let _ = UIGraphicsGetCurrentContext()
        let origin = CGPoint(x: insets.left, y: insets.top)
        self.draw(at: origin)
        let imageWithInsets = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return imageWithInsets
    }
}

OLD ANSWER ：

import UIKit

extension UIImage {
    func imageWithInsets(insets: UIEdgeInsets) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(
            CGSizeMake(self.size.width + insets.left + insets.right,
                self.size.height + insets.top + insets.bottom), false, self.scale)
        let context = UIGraphicsGetCurrentContext()
        let origin = CGPoint(x: insets.left, y: insets.top)
        self.drawAtPoint(origin)
        let imageWithInsets = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return imageWithInsets
    }
}

Answer 2

您创建一个1000x1000的新图像上下文，在中间绘制旧图像，然后从上下文中获取新的UIImage。

// Setup a new context with the correct size
CGFloat width = 1000;
CGFloat height = 1000;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), NO, 0.0);        
CGContextRef context = UIGraphicsGetCurrentContext();       
UIGraphicsPushContext(context);                             

// Now we can draw anything we want into this new context.
CGPoint origin = CGPointMake((width - oldImage.size.width) / 2.0f,
                            (height - oldImage.size.height) / 2.0f);
[oldImage drawAtPoint:origin];

// Clean up and get the new image.
UIGraphicsPopContext();                             
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Answer 3

这是受鼓手B回答的 Swift 4 的解决方案：

import UIKit

extension UIImage {

    func addImagePadding(x: CGFloat, y: CGFloat) -> UIImage? {
        let width: CGFloat = size.width + x
        let height: CGFloat = size.height + y
        UIGraphicsBeginImageContextWithOptions(CGSize(width: width, height: height), false, 0)
        let origin: CGPoint = CGPoint(x: (width - size.width) / 2, y: (height - size.height) / 2)
        draw(at: origin)
        let imageWithPadding = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return imageWithPadding
    }
}

如何申请：

let image = UIImage(named: "your-image")!
let imageView = UIImageView(image: image.addImagePadding(x: 50, y: 50))
imageView.backgroundColor = UIColor.gray
view.addSubview(imageView)

特点：

• 只需通过参数
传递填充值
• 彩色填充（通过将UIGraphicsBeginImageContextWithOptions opaque参数设置为false）

Answer 4

在UIImage上创建一个类别，然后尝试：

+ (UIImage *)imageWithInsets:(CGRect)insetRect image:(UIImage *)image {
    CGRect newRect = CGRectMake(0.0, 0.0, insetRect.origin.x+insetRect.size.width+image.size.width, insetRect.origin.y+insetRect.size.height+image.size.height);
    // Setup a new context with the correct size
    UIGraphicsBeginImageContextWithOptions(newRect.size, NO, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    UIGraphicsPushContext(context);

    // Now we can draw anything we want into this new context.
    CGPoint origin = CGPointMake(insetRect.origin.x, insetRect.origin.y);
    [image drawAtPoint:origin];

    // Clean up and get the new image.
    UIGraphicsPopContext();
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

Answer 5

通过更好的命名约定对appsunited的答案进行了修复。为了不混淆它，函数是否在变异：

extension UIImage {
    func withPadding(_ padding: CGFloat) -> UIImage? {
        return withPadding(x: padding, y: padding)
    }

    func withPadding(x: CGFloat, y: CGFloat) -> UIImage? {
        let newWidth = size.width + 2 * x
        let newHeight = size.height + 2 * y
        let newSize = CGSize(width: newWidth, height: newHeight)
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0)
        let origin = CGPoint(x: (newWidth - size.width) / 2, y: (newHeight - size.height) / 2)
        draw(at: origin)
        let imageWithPadding = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return imageWithPadding
    }
}