如何从UIImagePickerViewcontroller获取缩略图和原始图像？

Question

[从相机捕获照片后，我正在对图像进行压缩（400kb和1 Mb），在iPhone 6中看起来差不多3秒，而在iPhone 6s中不到1秒。是否有任何方法无需手动压缩即可获取缩略图和原始图像？

用于图像压缩的代码

UIImage的扩展名

extension UIImage {
    // MARK: - UIImage+Resize
    func compressTo(_ expectedSizeInMb:Int) -> Data? {
        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 = jpegData(compressionQuality: compressingValue) {
                if data.count < sizeInBytes {
                    needCompress = false
                    imgData = data
                } else {
                    compressingValue -= 0.1
                }
            }
        }

        if let data = imgData {
            if (data.count < sizeInBytes) {
                return data
            }
        }
        return nil
    }
}

用法：

if let imageData = image.compressTo(1) {
print(imageData)
 }

Answer 1

尝试使用“ AssetLibrary.framework”将图像写入相机胶卷，它将自动为您创建缩略图。而且，由于此过程是异步的，因此肯定会提高该应用程序的性能。

尝试以下操作：

Swift 5

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    /////.........
    let img = info[UIImagePickerController.InfoKey.originalImage] as? UIImage
    let library = ALAssetsLibrary()
    if let image = ALAssetOrientation(rawValue: img?.imageOrientation.rawValue) {
        library.writeImage(toSavedPhotosAlbum: img?.cgImage, orientation: image, completionBlock: { assetURL, error in
            if error != nil {
                print("error")
                return
            }

            library.asset(for: assetURL, resultBlock: { asset in
                if let aspect = asset?.aspectRatioThumbnail() {
                    self.imageViewer.image = UIImage(cgImage: aspect)
                } //self.imageViewer is a UIImageView to display thumbnail
            }, failureBlock: { error in
                print("Failed to load captured image.")
            })
        })
    }

    //................
}

目标c

#import <AssetsLibrary/AssetsLibrary.h>

////.........your code

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    /////.........
    UIImage* img = info[UIImagePickerControllerOriginalImage];
    ALAssetsLibrary *library = [ALAssetsLibrary new];  
    [library writeImageToSavedPhotosAlbum:[img CGImage] orientation:(ALAssetOrientation)[img imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error){  
        if (error) {  
            NSLog(@"error");  
            return;
        } 

        [library assetForURL:assetURL resultBlock:^(ALAsset *asset) {
            [self.imageViewer setImage:[UIImage imageWithCGImage:[asset aspectRatioThumbnail]]]; //self.imageViewer is a UIImageView to display thumbnail
        } failureBlock:^(NSError *error) {
            NSLog(@"Failed to load captured image.");
        }];
    }];  
    [library release];

    //................
    }

////......rest of your code

我尚未测试代码，但我希望它能够实现您的目的。在尝试尝试之前，请确保将“ AssetLibrary.framework”引用添加到您的项目中，并让我知道它是否对您有用。

Answer 2

尝试：

  let phAsset = info[UIImagePickerController.InfoKey.phAsset] as! PHAsset
  let options = PHImageRequestOptions()
  options.deliveryMode = .fastFormat
                         // you can change your target size to CGSize(width: Int , height:  Int) any number you want.
  PHImageManager.default().requestImage(for: phAsset, targetSize: PHImageManagerMaximumSize, contentMode: .default, options: options, resultHandler: { image , _ in

        let thumbnail = image
        // use tour thumbnail
    })