如何在上传到Parse作为PFFile之前压缩或减小图像的大小？（Swift）

Question

如何在上传到Parse作为PFFile之前压缩或减小图像的大小？（Swift）

iosswiftparse-platformuiimage

109

我尝试在手机上直接拍照后将图像文件上传到Parse，但是出现了异常：

未捕获的异常 'NSInvalidArgumentException'，原因：'PFFile不能大于10485760字节'

这是我的代码：

在第一个视图控制器中：

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if (segue.identifier == "getImage")
    {
        var svc = segue.destinationViewController as! ClothesDetail
        svc.imagePassed = imageView.image
    }
}

在上传图像的视图控制器中：

let imageData = UIImagePNGRepresentation(imagePassed)
let imageFile = PFFile(name: "\(picName).png", data: imageData)

var userpic = PFObject(className:"UserPic")
userpic["picImage"] = imageFile`

但我仍然需要将那张照片上传到 Parse。有没有办法减小图片的大小或分辨率？

- elvislkm

我尝试了gbk的最后一个建议，发现如果我调用let newData = UIImageJPEGRepresentation(UIImage(data: data), 1)，那么newData.count不等于data.count，并且实际上比data.count大得多，超过2倍。这对我来说真的很惊讶！无论如何，感谢提供代码！ - NicoD

14个回答

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- D Saggin · Answer 1

在Swift 4中，我创建了这个扩展程序，它将接收预期大小并尝试达到它。

extension UIImage {

    enum CompressImageErrors: Error {
        case invalidExSize
        case sizeImpossibleToReach
    }
    func compressImage(_ expectedSizeKb: Int, completion : (UIImage,CGFloat) -> Void ) throws {

        let minimalCompressRate :CGFloat = 0.4 // min compressRate to be checked later

        if expectedSizeKb == 0 {
            throw CompressImageErrors.invalidExSize // if the size is equal to zero throws
        }

        let expectedSizeBytes = expectedSizeKb * 1024
        let imageToBeHandled: UIImage = self
        var actualHeight : CGFloat = self.size.height
        var actualWidth : CGFloat = self.size.width
        var maxHeight : CGFloat = 841 //A4 default size I'm thinking about a document
        var maxWidth : CGFloat = 594
        var imgRatio : CGFloat = actualWidth/actualHeight
        let maxRatio : CGFloat = maxWidth/maxHeight
        var compressionQuality : CGFloat = 1
        var imageData:Data = UIImageJPEGRepresentation(imageToBeHandled, compressionQuality)!
        while imageData.count > expectedSizeBytes {

            if (actualHeight > maxHeight || actualWidth > maxWidth){
                if(imgRatio < maxRatio){
                    imgRatio = maxHeight / actualHeight;
                    actualWidth = imgRatio * actualWidth;
                    actualHeight = maxHeight;
                }
                else if(imgRatio > maxRatio){
                    imgRatio = maxWidth / actualWidth;
                    actualHeight = imgRatio * actualHeight;
                    actualWidth = maxWidth;
                }
                else{
                    actualHeight = maxHeight;
                    actualWidth = maxWidth;
                    compressionQuality = 1;
                }
            }
            let rect = CGRect(x: 0.0, y: 0.0, width: actualWidth, height: actualHeight)
            UIGraphicsBeginImageContext(rect.size);
            imageToBeHandled.draw(in: rect)
            let img = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
                if let imgData = UIImageJPEGRepresentation(img!, compressionQuality) {
                if imgData.count > expectedSizeBytes {
                    if compressionQuality > minimalCompressRate {
                        compressionQuality -= 0.1
                    } else {
                        maxHeight = maxHeight * 0.9
                        maxWidth = maxWidth * 0.9
                    }
                }
                imageData = imgData
            }


        }

        completion(UIImage(data: imageData)!, compressionQuality)
    }


}

使用方法：

        do {
            try UiImageView.image?.compressImage(100, completion: { (image, compressRatio) in
                print(image.size) 
                imageData = UIImageJPEGRepresentation(image, compressRatio)
                base64data = imageData?.base64EncodedString()

            })
        } catch {
                 print("Error")
        }

- fozoglu · Answer 2

Swift 3

@leo-dabus的答案已经更新为Swift 3。

    extension UIImage {
    var uncompressedPNGData: Data?      { return UIImagePNGRepresentation(self)        }
    var highestQualityJPEGNSData: Data? { return UIImageJPEGRepresentation(self, 1.0)  }
    var highQualityJPEGNSData: Data?    { return UIImageJPEGRepresentation(self, 0.75) }
    var mediumQualityJPEGNSData: Data?  { return UIImageJPEGRepresentation(self, 0.5)  }
    var lowQualityJPEGNSData: Data?     { return UIImageJPEGRepresentation(self, 0.25) }
    var lowestQualityJPEGNSData:Data?   { return UIImageJPEGRepresentation(self, 0.0)  }
}

- mendidou · Answer 3

我发现最简单的方法是

extension UIImage {

    func compressImage(with maxSizeInBytes: Int ) -> UIImage? {
        if maxSizeInBytes < 0 {
            return nil
        }
        var currentImage:UIImage? = self
        var divideQuality:CGFloat = 1.0
        var imageData = self.jpegData(compressionQuality:divideQuality )
        while imageData!.count > maxSizeInBytes {
            divideQuality = divideQuality/2
            imageData = currentImage?.jpegData(compressionQuality: divideQuality)
        }
        guard let data = imageData else {
            return nil
        }
        currentImage = UIImage(data: data)
        return UIImage(data: (currentImage?.jpegData(compressionQuality: divideQuality)) as! Data)
    }
 
}

- Fadi Abuzant · Answer 4

这是最短的方法：

func compressToMaxMB(_ maxMB: Double) -> Data? {
    let currentSize = Double(self.jpegData(compressionQuality: 1)?.count ?? 0)
    let quality: CGFloat = (maxMB * 1000000) / currentSize
    return self.jpegData(compressionQuality: quality)
}