How to calculate the average color of a UIImage?

Question

I want to build an app that lets the user select an image and it outputs the \"average color\".

For example, this image:

The average color would be a gr

Answer 1

Maybe it can help for someone - my extension return color but for UIView (where your image can be found), uses old QuartzCore code

// ObjC case
@interface UIView (ColorOfPoint)
    - (UIColor *) colorOfPoint:(CGPoint)point withSize:(CGSize)size;
@end

#import 

@implementation UIView (ColorOfPoint)

- (UIColor *) colorOfPoint:(CGPoint)point withSize:(CGSize)size {
    unsigned char pixel[4] = {0};

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef context = CGBitmapContextCreate(pixel, size.width, size.height, 8, 4, colorSpace, kCGBitmapAlphaInfoMask & kCGImageAlphaPremultipliedLast);

    CGContextTranslateCTM(context, -point.x-size.width/2, -point.y-size.height/2);

    [self.layer renderInContext:context];

    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    //NSLog(@"pixel: %d %d %d %d", pixel[0], pixel[1], pixel[2], pixel[3]);

    UIColor *color = [UIColor colorWithRed:pixel[0]/255.0 green:pixel[1]/255.0 blue:pixel[2]/255.0 alpha:pixel[3]/255.0];

    return color;
}

@end