从UIImageView获取一个调整大小的图像

Question

我需要将图像数据上传到我的Parse.com后端，但我发现我的图片太大了，尺寸明智。NSHipster有一篇关于图像大小调整的文章，代码如下:

import ImageIO
if let imageSource = CGImageSourceCreateWithURL(self.URL, nil) {
    let options: CFDictionary = [
        kCGImageSourceThumbnailMaxPixelSize: max(size.width, size.height) / 2.0,
        kCGImageSourceCreateThumbnailFromImageIfAbsent: true
    ]
    let scaledImage = CGImageSourceCreateThumbnailAtIndex(imageSource, 0, options).flatMap { UIImage(CGImage: $0) }
}

不幸的是，这段代码不能在Swift 1.2中编译。特别是有两个问题。CFDictionary无法初始化，flatMap方法无法识别。

Answer 1

下面是一些调整图片大小的函数:

import UIKit
func RBSquareImageTo(image: UIImage, size: CGSize) -> UIImage {
    return RBResizeImage(RBSquareImage(image), size)
}
func RBSquareImage(image: UIImage) -> UIImage {
    var originalWidth  = image.size.width
    var originalHeight = image.size.height
    var edge: CGFloat
    if originalWidth > originalHeight {
        edge = originalHeight
    } else {
        edge = originalWidth
    }
    var posX = (originalWidth  - edge) / 2.0
    var posY = (originalHeight - edge) / 2.0
    var cropSquare = CGRectMake(posX, posY, edge, edge)
    var imageRef = CGImageCreateWithImageInRect(image.CGImage, cropSquare);
    return UIImage(CGImage: imageRef, scale: UIScreen.mainScreen().scale, orientation: image.imageOrientation)
}
func RBResizeImage(image: UIImage, targetSize: CGSize) -> UIImage {
    let size = image.size
    let widthRatio  = targetSize.width  / image.size.width
    let heightRatio = targetSize.height / image.size.height
    // Figure out what our orientation is, and use that to form the rectangle
    var newSize: CGSize
    if(widthRatio > heightRatio) {
        newSize = CGSizeMake(size.width * heightRatio, size.height * heightRatio)
    } else {
        newSize = CGSizeMake(size.width * widthRatio,  size.height * widthRatio)
    }
    // This is the rect that we've calculated out and this is what is actually used below
    let rect = CGRectMake(0, 0, newSize.width, newSize.height)
    // Actually do the resizing to the rect using the ImageContext stuff
    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    image.drawInRect(rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
}

。

Answer 2

这是根据参数缩放图像的Objective C代码。

-(UIImage*)imageWithImage:(UIImage*)image
              scaledToSize:(CGSize)newSize;
{
    UIGraphicsBeginImageContext( newSize );
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}