將UIImage轉換為NSData並返回UIImage

Question

我必須從數據庫中填充表格單元格，並且圖像在設備上。 我要將該圖像存儲在imageDataObject ，如何將該UIImage轉換為NSData 。 請建議，我嘗試了很多解決方案，但它沒有將NSData轉換回UIImage 。

    cell.textLabel.text = [[offlineImageListArray objectAtIndex:indexPath.row] imageName];
    UIImage *thumbnail = [self retrieveImageFromDevice:[[offlineImageListArray objectAtIndex:indexPath.row] imageName]];
    NSData* data = ??????????;
    ImageData *imageDataObject = [[ImageData alloc] initWithImageId:[[offlineImageListArray objectAtIndex:indexPath.row]imageId] 
    imageName:[[offlineImageListArray objectAtIndex:indexPath.row] imageName] imageData:data];
    [imagesArray addObject:imageDataObject];

Answer 1

要將UIImage轉換為NSData ，請使用UIImageJPEGRepresentation(UIImage *image, CGFloat compressionQuality)或UIImagePNGRepresentation(UIImage *image)

要將NSData轉換為UIImage ，請使用[UIImage imageWithData:imageData]

所以你的例子看起來像這樣：

cell.textLabel.text = [[offlineImageListArray objectAtIndex:indexPath.row] imageName];
UIImage *thumbnail = [self retrieveImageFromDevice:[[offlineImageListArray objectAtIndex:indexPath.row] imageName]];
NSData* data = UIImagePNGRepresentation(thumbnail);
ImageData *imageDataObject = [[ImageData alloc] initWithImageId:[[offlineImageListArray objectAtIndex:indexPath.row]imageId] imageName:[[offlineImageListArray objectAtIndex:indexPath.row] imageName] imageData:data];
[imagesArray addObject:imageDataObject];

參考文獻： https ： //developer.apple.com/LIBRARY/IOS/documentation/UIKit/Reference/UIKitFunctionReference/Reference/reference.html https://developer.apple.com/Library/ios/documentation/UIKit/Reference/UIImage_Class /Reference/Reference.html

Answer 2

試試這個：

使用UIImage轉換為NSData 。

  NSData *imagedata = UIImagePNGRepresentation(thumbnail);

嘗試將此圖像數據轉換回UIImage

  UIImage *image= [UIImage imageWithData:imagedata];

Answer 3

在Swift版本中：

    let imageData = UIImagePNGRepresentation(image!)!
    let imageFromData = UIImage(data: imageData)

Answer 4

使用if-let阻止數據以防止應用程序崩潰和安全執行代碼，因為函數UIImagePNGRepresentation返回一個可選值。

if let img = UIImage(named: "TestImage.png") {
    if let data:Data = UIImagePNGRepresentation(img) {
       // Handle operations with data here...         
    }
}

注意： 數據是Swift 3類。 在Swift 3中使用Data而不是NSData

通用圖像操作（如png和jpg）：

if let img = UIImage(named: "TestImage.png") {  //UIImage(named: "TestImage.jpg")
        if let data:Data = UIImagePNGRepresentation(img) {
               handleOperationWithData(data: data)     
        } else if let data:Data = UIImageJPEGRepresentation(img, 1.0) {
               handleOperationWithData(data: data)     
        }
}

*******
func handleOperationWithData(data: Data) {
     // Handle operations with data here...
     if let image = UIImage(data: data) {
        // Use image...
     }
}

通過使用擴展名：

extension UIImage {

    var pngRepresentationData: Data? {
        return UIImagePNGRepresentation(img)
    }

    var jpegRepresentationData: Data? {
        return UIImageJPEGRepresentation(self, 1.0)
    }
}

*******
if let img = UIImage(named: "TestImage.png") {  //UIImage(named: "TestImage.jpg")
      if let data = img.pngRepresentationData {
              handleOperationWithData(data: data)     
      } else if let data = img.jpegRepresentationData {
              handleOperationWithData(data: data)     
     }
}

*******
func handleOperationWithData(data: Data) {
     // Handle operations with data here...
     if let image = UIImage(data: data) {
        // Use image...
     }
}

Answer 5

從圖像轉換數據：

請嘗試JPEG或PNG表示，具體取決於您的圖像格式：

UIImageJPEGRepresentation

以JPEG格式返回指定圖像的數據。

NSData * UIImageJPEGRepresentation (
   UIImage *image,
   CGFloat compressionQuality
);

UIImagePNGRepresentation

以PNG格式返回指定圖像的數據

NSData * UIImagePNGRepresentation (
   UIImage *image
);

例：

extension UIImage {

    var pngRepresentationData: Data? {
        return UIImagePNGRepresentation(img)
    }

    var jpegRepresentationData: Data? {
        return UIImageJPEGRepresentation(self, 1.0)
    }
}

使用：

let data = myImage.jpegRepresentationData
let data1 = myImage.pngRepresentationData

從數據轉換圖像：

let image = UIImage(data: data)