NSData and UIImage

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.

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];

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."

Try this to convert an image to NSdata:

UIImage *img = [UIImage imageNamed:@"image.png"];
NSData *data1 = UIImagePNGRepresentation(img);

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.

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...
     }
}