在以PFFile格式上传到Parse之前，如何压缩缩小图像的大小？（迅速）

Question

直接在手机上拍照后，我试图将图像文件上传到Parse。但这会引发异常：由于未捕获的异常“ NSInvalidArgumentException”而终止应用程序，原因：“ PFFile不能大于10485760字节”这是我的代码：在第一视图控制器中：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`但是我仍然需要将照片上传到Parse。有什么方法可以减小图像的尺寸或分辨率？

Answer 1

是的，你可以使用UIImageJPEGRepresentation，而不是UIImagePNGRepresentation减少图像文件的大小。您可以按照以下方式创建扩展UIImage：

Xcode 8.2•Swift 3.0.2

extension UIImage {

    enum JPEGQuality: CGFloat {

        case lowest  = 0

        case low     = 0.25

        case medium  = 0.5

        case high    = 0.75

        case highest = 1

    }

    /// Returns the data for the specified image in JPEG format.

    /// If the image object’s underlying image data has been purged, calling this function forces that data to be reloaded into memory.

    /// - returns: A data object containing the JPEG data, or nil if there was a problem generating the data. This function may return nil if the image has no data or if the underlying CGImageRef contains data in an unsupported bitmap format.

    func jpeg(_ quality: JPEGQuality) -> Data? {

        return UIImageJPEGRepresentation(self, quality.rawValue)

    }

}

编辑/更新：

Xcode 10 Swift 4.2

extension UIImage {

    enum JPEGQuality: CGFloat {

        case lowest  = 0

        case low     = 0.25

        case medium  = 0.5

        case high    = 0.75

        case highest = 1

    }

    /// Returns the data for the specified image in JPEG format.

    /// If the image object’s underlying image data has been purged, calling this function forces that data to be reloaded into memory.

    /// - returns: A data object containing the JPEG data, or nil if there was a problem generating the data. This function may return nil if the image has no data or if the underlying CGImageRef contains data in an unsupported bitmap format.

    func jpeg(_ jpegQuality: JPEGQuality) -> Data? {

        return jpegData(compressionQuality: jpegQuality.rawValue)

    }

}

用法：

if let imageData = image.jpeg(.lowest) {

    print(imageData.count)

}

Answer 2

如果要将图像大小限制为某个具体值，可以执行以下操作：

import UIKit

extension UIImage {

    // MARK: - UIImage+Resize

    func compressTo(_ expectedSizeInMb:Int) -> UIImage? {

        let sizeInBytes = expectedSizeInMb * 1024 * 1024

        var needCompress:Bool = true

        var imgData:Data?

        var compressingValue:CGFloat = 1.0

        while (needCompress && compressingValue > 0.0) {

        if let data:Data = UIImageJPEGRepresentation(self, compressingValue) {

            if data.count < sizeInBytes {

                needCompress = false

                imgData = data

            } else {

                compressingValue -= 0.1

            }

        }

    }

    if let data = imgData {

        if (data.count < sizeInBytes) {

            return UIImage(data: data)

        }

    }

        return nil

    } 

}

Answer 3

Jus Fixing for Xcode 7，于09/21/2015测试，工作正常：

只需创建一个扩展UIImage，如下所示：

extension UIImage

{

    var highestQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 1.0)! }

    var highQualityJPEGNSData: NSData    { return UIImageJPEGRepresentation(self, 0.75)!}

    var mediumQualityJPEGNSData: NSData  { return UIImageJPEGRepresentation(self, 0.5)! }

    var lowQualityJPEGNSData: NSData     { return UIImageJPEGRepresentation(self, 0.25)!}

    var lowestQualityJPEGNSData: NSData  { return UIImageJPEGRepresentation(self, 0.0)! }

}

然后，您可以像这样使用它：

let imageData = imagePassed.lowestQualityJPEGNSData