NSData and UIImage - ios

Question

I am trying to load UIImage object from NSData, and the sample code was to NSImage, I guess they should be the same. But just now loading the image, I am wondering what's the best to troubleshoot the UIImage loading NSData issue.

Answer 1

I didn't try UIImageJPEGRepresentation() before, but UIImagePNGRepresentation works fine for me, and conversion between NSData and UIImage is dead simple:
NSData *imageData = UIImagePNGRepresentation(image);
UIImage *image=[UIImage imageWithData:imageData];

Answer 2

UIImage has an -initWithData: method. From the docs: "The data in the data parameter must be formatted to match the file format of one of the system’s supported image types."

Answer 3

Try this to convert an image to NSdata:
UIImage *img = [UIImage imageNamed:#"image.png"];
NSData *data1 = UIImagePNGRepresentation(img);

Answer 4

theData should be a NSData object which already contains the data. You need to do the file loading/downloading to the NSData object before it is used. You can inspect it by using NSLog on theData and see if it contains the valid data.

Answer 5

For safe execution of code, use if-let block with Data, as function UIImagePNGRepresentation returns, optional value.
if let img = UIImage(named: "Hello.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: "Hello.png") {
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: "Hello.png") {
if let data = img.pngRepresentationData {
handleOperationWithData(data: data)
} else if let data = jpegRepresentationData {
handleOperationWithData(data: data)
}
}
*******
func handleOperationWithData(data: Data) {
// Handle operations with data here...
if let image = UIImage(data: data) {
// Use image...
}
}