ios - 照片调整大小和压缩

Question

我正在调整照片大小并压缩照片，这是一个不寻常的结果。

当我从相册中选择图像时，图像会很好地压缩和调整大小。但是，如果我在从相机传递的图像上执行此操作，则图像会变得异常小(并且无法观看)。我所做的测试是在按钮中分配一些压缩和调整大小功能，该按钮从相机源或相册中获取图像。下面是我的代码和控制台输出

@IBAction func testBtnPressed(sender: AnyObject) {
    let img = selectedImageView.image!
    print("before resize image \(img.dataLengh_kb)kb size \(img.size)")
    
    let resizedImg = img.resizeWithWidth(1080)
    print("1080 After resize image \(resizedImg!.dataLengh_kb)kb size \(resizedImg!.size)")
    
    let compressedImageData = resizedImg!.mediumQualityJPEGNSData
    print("Compress to medium quality = \(compressedImageData.length / 1024)kb")
}

extension UIImage {
    var mediumQualityJPEGNSData: NSData  { return UIImageJPEGRepresentation(self, 0.5)!  }
    
    func resizeWithWidth(width: CGFloat) -> UIImage? {
        let imageView = UIImageView(frame: CGRect(origin: .zero, size: CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))))
        imageView.contentMode = .ScaleAspectFit
        imageView.image = self
        UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, false, scale)
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        imageView.layer.renderInContext(context)
        guard let result = UIGraphicsGetImageFromCurrentImageContext() else { return nil }
        UIGraphicsEndImageContext()
        return result
    }
}

从相册中选择照片时

before resize image 5004kb size (3024.0, 3024.0)

1080 After resize image 1023kb size (1080.0, 1080.0)

Compress to medium quality = 119kb

当照片通过相机时

before resize image 4653kb size (24385.536, 24385.536)

1080 After resize image 25kb size (1080.576, 1080.576)

Compress to medium quality = 4kb

Answer 1

我已将图像调整大小功能替换为以下功能，效果好多了

func resizeImage(newHeight: CGFloat) -> UIImage {

    let scale = newHeight / self.size.height
    let newWidth = self.size.width * scale
    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight))
    self.drawInRect(CGRectMake(0, 0, newWidth, newHeight))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage
}