convert UIImage to NSData

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);