color picker

UIImage+Picker.h

//
//  UIImage+Picker.h
//
//  Created by hiro on 02/18/2013.
//  Copyright (c) 2013 sign g.k. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIImage (Picker)
-(NSString *)colorAtPosition:(CGPoint)position;
@end

UIImage+Picker.m

//
//  UIImage+Picker.m
//
//  Created by hiro on 02/18/2013.
//  Copyright (c) 2013 sign g.k. All rights reserved.
//


#import "UIImage+Picker.h"

@implementation UIImage (Picker)

-(NSString *)colorAtPosition:(CGPoint)position {  
  CGRect sourceRect = CGRectMake(position.x, position.y, 1.f, 1.f);
  CGImageRef imageRef = CGImageCreateWithImageInRect(self.CGImage, sourceRect);
  
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  unsigned char *buffer = malloc(4);
  CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big;
  CGContextRef context = CGBitmapContextCreate(buffer, 1, 1, 8, 4, colorSpace, bitmapInfo);
  CGColorSpaceRelease(colorSpace);
  CGContextDrawImage(context, CGRectMake(0.f, 0.f, 1.f, 1.f), imageRef);
  CGImageRelease(imageRef);
  CGContextRelease(context);
  
  CGFloat r = buffer[0] / 255.f;
  CGFloat g = buffer[1] / 255.f;
  CGFloat b = buffer[2] / 255.f;
  CGFloat a = buffer[3] / 255.f;
  
  free(buffer);
  return [NSString stringWithFormat:@"%f,%f,%f,%f", r, g, b, a];
//  return [UIColor colorWithRed:r green:g blue:b alpha:a];
}

@end