convert UIImage to NSData and back to UIImage

Question

I have to populate table cell from database and images are on device. I've to store that image in imageDataObject, how to convert that UIImage to NSData. Please suggest, I tried many solution but it's not converting back that NSData to 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];

possible duplicate of [convert UIImage to NSData](http://stackoverflow.com/questions/6476929/convert-uiimage-to-nsdata) — CRDave, Nov 16 '13 at 05:33
possible duplicate of [How to convert NSData value to UIImage](http://stackoverflow.com/questions/10101526/how-to-convert-nsdata-value-to-uiimage) — Akshit Zaveri, Nov 16 '13 at 06:03
possible duplicate of [NSData to UIImage](http://stackoverflow.com/questions/2240765/nsdata-to-uiimage) — Undo, Dec 31 '13 at 15:04

score 18 · Accepted Answer · answered Nov 16 '13 at 05:57

To convert UIImage to NSData, use either UIImageJPEGRepresentation(UIImage *image, CGFloat compressionQuality) or UIImagePNGRepresentation(UIImage *image)

To convert NSData to UIImage, use [UIImage imageWithData:imageData]

So your example could look like this:

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];

References: 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

What if I do not know the image representation wether png or jpg? Is it a problem if I use `UIImagePNGRepresentation` for jpg too? — János, Jan 07 '15 at 09:54

score 9 · Answer 2 · edited Nov 16 '13 at 06:02

9

Try With this:

Use this for convert UIImage to NSData.

  NSData *imagedata = UIImagePNGRepresentation(thumbnail);

Try this for image data convert back to UIImage

  UIImage *image= [UIImage imageWithData:imagedata];

edited Nov 16 '13 at 06:02

Akshit Zaveri

4,166
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answered Nov 16 '13 at 05:29

Pradhyuman sinh

3,936
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How the hell do i know the UIImage is PNG? What if it's JPEG? – TomSawyer Jun 28 '16 at 19:46
A UIImage is neither jpg or png. it's a raw bitmap. PNG and JPG are a format to transport an image in a smaller format – Toad Jul 18 '17 at 12:09

Bilal Arslan · Answer 3 · 2022-06-15T10:53:24.607

4

in Swift version:

    let imageData = image!.pngData()
    let imageFromData = UIImage(data: imageData)

See: https://developer.apple.com/documentation/uikit/uiimage/1624096-pngdata

edited Jun 15 '22 at 10:53

answered May 14 '16 at 15:32

Bilal Arslan

307
3
10

Simple, effective! Thanks! – user4806509 Jul 17 '17 at 14:47
Simple doc update, as now 'UIImagePNGRepresentation' has been replaced by instance method 'UIImage.pngData()' – kikeenrique Jun 15 '22 at 10:15

score 0 · Answer 4 · answered Oct 25 '17 at 17:08

Use if-let block with Data to prevent app crash & safe execution of code, as function UIImagePNGRepresentation returns an optional value.

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

Note: Data is Swift 3 class. Use Data instead of NSData with Swift 3

Generic image operations (like png & jpg both):

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...
     }
}

By using extension:

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...
     }
}

score 0 · Answer 5 · answered Apr 27 '19 at 06:35

Convert Data from Image:

Try JPEG or PNG representation depending on your image format:

UIImageJPEGRepresentation

Returns the data for the specified image in JPEG format.

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

UIImagePNGRepresentation

Returns the data for the specified image in PNG format

NSData * UIImagePNGRepresentation (
   UIImage *image
);

Example:

extension UIImage {

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

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

Use:

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

Convert Image from Data:

let image = UIImage(data: data)

convert UIImage to NSData and back to UIImage

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