How to get Size of UIImage in Bytes in iOS 4.0+?

Question

I am trying to pick an image from the photo library or from the camera.
The delegate method:

- (void)imagePickerController:(UIImagePickerController *)picker d         


        

Answer 1

I know this is an old question but creating a NSData object just to get the byte-size of an image can be a really expensive operation. Image can have over 20Mb and creating equally sized object just to get the size of the first one...

I tend to use this category:

UIImage+CalculatedSize.h

#import 

@interface UIImage (CalculatedSize)

-(NSUInteger)calculatedSize;

@end

UIImage+CalculatedSize.m

#import "UIImage+CalculatedSize.h"

@implementation UIImage (CalculatedSize)

-(NSUInteger)calculatedSize
{    
    return CGImageGetHeight(self.CGImage) * CGImageGetBytesPerRow(self.CGImage);
}

@end

You simply import the UIImage+CalculatedSize.h and use it like this:

NSLog (@"myImage size is: %u",myImage.calculatedSize);

Or, if you want to avoid using categories:

NSUInteger imgSize  = CGImageGetHeight(anImage.CGImage) * CGImageGetBytesPerRow(anImage.CGImage);

EDIT:

This calculation of course has nothing to do with JPEG/PNG compression. It relates to underlaying CGimage:

A bitmap (or sampled) image is a rectangular array of pixels, with each pixel representing a single sample or data point in a source image.

In a way a size retrieved this way gives you a worst-case scenario information without actually creating an expensive additional object.