gistfile1.m

//
//  UIImageView+RatingStar.h
//  RatingImageDemo
//
//  Created by Alex Rezit on 25/01/2013.
//  Copyright (c) 2013 Seymour Dev. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIImageView (RatingStar)

- (void)setImageWithRating:(float)rating;

@end

gistfile2.m

//
//  UIImageView+RatingStar.m
//  RatingImageDemo
//
//  Created by Alex Rezit on 25/01/2013.
//  Copyright (c) 2013 Seymour Dev. All rights reserved.
//

#import "UIImageView+RatingStar.h"

float const kRatingFullScore = 10.0f;
NSUInteger const kRatingNumberOfStars = 5;

@implementation UIImageView (RatingStar)

- (void)setImageWithRating:(float)rating
{
    UIImage *filledStar = [UIImage imageNamed:@"rating_star_filled"];
    UIImage *hollowStar = [UIImage imageNamed:@"rating_star_hollow"];
    
    CGFloat width = filledStar.size.width;
    CGFloat height = filledStar.size.height;
    
    CGSize imageSize = CGSizeMake(width * kRatingNumberOfStars, height);
    UIGraphicsBeginImageContext(imageSize);
    
    [hollowStar drawAsPatternInRect:CGRectMake(0, 0, imageSize.width, imageSize.height)];
    [filledStar drawAsPatternInRect:CGRectMake(0, 0, width * (rating / kRatingFullScore * kRatingNumberOfStars), height)];
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    self.image = image;
}

@end