convert UIImage to NSData

Question

I am using this code in my app which will help me to send a image.

However, I have an image view with an image. I have no file in appbundle but have the image in my side. How can I change the below code ? Can anyone tell me how can I convert myimage to NSData ?

// Attach an image to the email
NSString *path = [[NSBundle mainBundle] pathForResource:@"rainy" ofType:@"jpg"];
NSData *myData = [NSData dataWithContentsOfFile:path];
[picker addAttachmentData:myData mimeType:@"image/jpeg" fileName:@"rainy"];

Solution 1

Try one of the following, 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
);

Here the docs.

EDIT:

if you want to access the raw bytes that make up the UIImage, you could use this approach:

CGDataProviderRef provider = CGImageGetDataProvider(image.CGImage);
NSData* data = (id)CFBridgingRelease(CGDataProviderCopyData(provider));
const uint8_t* bytes = [data bytes];

This will give you the low-level representation of the image RGB pixels. (Omit the CFBridgingRelease bit if you are not using ARC).

Solution 2

NSData *imageData = UIImagePNGRepresentation(myImage.image);

Solution 3

If you have an image inside a UIImageView , e.g. "myImageView", you can do the following:

Convert your image using UIImageJPEGRepresentation() or UIImagePNGRepresentation() like this:

NSData *data = UIImagePNGRepresentation(myImageView.image);
//or
NSData *data = UIImageJPEGRepresentation(myImageView.image, 0.8);
//The float param (0.8 in this example) is the compression quality 
//expressed as a value from 0.0 to 1.0, where 1.0 represents 
//the least compression (or best quality).

You can also put this code inside a GCD block and execute in another thread, showing an UIActivityIndicatorView during the process ...

//*code to show a loading view here*

dispatch_queue_t myQueue = dispatch_queue_create("com.my.queue", DISPATCH_QUEUE_SERIAL);

dispatch_async(myQueue, ^{ 

    NSData *data = UIImagePNGRepresentation(myImageView.image);
    //some code....

    dispatch_async( dispatch_get_main_queue(), ^{
        //*code to hide the loading view here*
    });
});

Solution 4

Create the reference of image....

UIImage *rainyImage = [UIImage imageNamed:@"rainy.jpg"];

displaying image in image view... imagedisplay is reference of imageview:

imagedisplay.image = rainyImage;

convert it into NSData by passing UIImage reference and provide compression quality in float values:

NSData *imgData = UIImageJPEGRepresentation(rainyImage, 0.9);

Solution 5

Solution in Swift 4

extension UIImage {
    var data : Data? {
      return cgImage?.dataProvider?.data as Data?
    }
}

View more solutions

Comments

[Himanshu Agnihotri]

UIImageJPEGRepresentation,UIImagePNGRepresentation both return nsdata of the image.....

[user2128531]

I am using this line but this is very slow

[devios1]

Is there a way to just get the data in whatever format it is already in?

[mostruash]

Xcode suggests me to use (id)CFBridgingRelease(CGDataProviderCopyData(provider)) to take the ownership of CDataRef returned by CGDataProviderCopyData in ARC.

[sergio]

@mostruash: thanks, I have modified my answer to take into account your suggestion.

[mostruash]

@sergio I'm not experienced with non-ARC Obj-C and I wonder if releasing data would be enough or if there would still be a memory leak.

[sergio]

@mostruash: in non-ARC case, there is no concept of ownership; the programmer should ensure that each object be released for any retain it received. In the present case, by releasing data you would ensure the object is properly deallocated: CGDataProviderCopyData gives you a retain count of 1; be releasing the object, you make it to be dealloc-ed.

[mostruash]

@sergio Thanks for the clarification.

[Yony]

Note that imageFlags (like imageOrientation) get lost when using UIImagePNGRepresentation. That's why UIImageJPEGRepresentation is preferred.

[Yony]

Note that imageFlags (like imageOrientation) get lost when using UIImagePNGRepresentation. That's why UIImageJPEGRepresentation is preferred

[hbk]

awesome! save ton of time (last approach)

[King-Wizard]

This won't help. The property CIImage is only set if it was initialized with imageWithCIImage:. Also this isn't directly the used data but rather another image representation object.

[Manuel]

How is the cgImage.dataProvider data encoded? It seems to be different from the data of UIImagePNGRepresentation and UIImageJPEGRepresentation because it cannot be used to create an image like so UIImage(data: imageData).

[Charlton Provatas]

@Manuel Not sure. I just converted the syntax from Sergio 's answer. Sergio would probably know better.

[Charlton Provatas]

@Manuel I'm assuming because it's using CoreGraphics API it's giving a lower-level data representation of the image than what UIImageJPEGRepresentation provides. But I believe this solution preserves the original encoding format that the image was in and doesn't re-encode it.