average color value of UIImage in Objective-C - objective-c

Question

I need the average color value of an image in objective c. I want to create a color gradient of it.
Has anyone an idea?

Answer 1

here is an experimental code that i have not tested yet.
struct pixel {
unsigned char r, g, b, a;
};
- (UIColor*) getDominantColor:(UIImage*)image
{
NSUInteger red = 0;
NSUInteger green = 0;
NSUInteger blue = 0;
// Allocate a buffer big enough to hold all the pixels
struct pixel* pixels = (struct pixel*) calloc(1, image.size.width * image.size.height * sizeof(struct pixel));
if (pixels != nil)
{
CGContextRef context = CGBitmapContextCreate(
(void*) pixels,
image.size.width,
image.size.height,
8,
image.size.width * 4,
CGImageGetColorSpace(image.CGImage),
kCGImageAlphaPremultipliedLast
);
if (context != NULL)
{
// Draw the image in the bitmap
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, image.size.width, image.size.height), image.CGImage);
// Now that we have the image drawn in our own buffer, we can loop over the pixels to
// process it. This simple case simply counts all pixels that have a pure red component.
// There are probably more efficient and interesting ways to do this. But the important
// part is that the pixels buffer can be read directly.
NSUInteger numberOfPixels = image.size.width * image.size.height;
for (int i=0; i<numberOfPixels; i++) {
red += pixels[i].r;
green += pixels[i].g;
blue += pixels[i].b;
}
red /= numberOfPixels;
green /= numberOfPixels;
blue/= numberOfPixels;
CGContextRelease(context);
}
free(pixels);
}
return [UIColor colorWithRed:red/255.0f green:green/255.0f blue:blue/255.0f alpha:1.0f];
}
You can use this method eg;
-(void)doSomething
{
UIImage *image = [UIImage imageNamed:#"someImage.png"];
UIColor *dominantColor = [self getDominantColor:image];
}
I hope this will work for you.
Also you can implement in UIImage with category. Better way to write some utilities for objects :)
Edit : Fixed the bug in while().

Answer 2

There is a method to create the average color from Image.
[UIColor colorWithAverageColorFromImage:(UIImage *)image];