convert UIImage to NSData and back to UIImage - ios

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];

Answer 1

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

Answer 2

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];

Answer 3

in Swift version:
let imageData = image!.pngData()
let imageFromData = UIImage(data: imageData)
See: https://developer.apple.com/documentation/uikit/uiimage/1624096-pngdata

Answer 4

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...
}
}

Answer 5

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)