starview is coming out black when scale is smaller

gistfile1.txt

//
// Created by georgecook on 13/05/2012.
//
// To change the template use AppCode | Preferences | File Templates.
//


#import "TTStarView.h"
#import "UIView+FrameAdditions.h"

#define kMaxStars 5
#define kStarWidth 47
#define kStarHeight 45
#define kGap 5


static UIImage *_starHighlightedImage;
static UIImage *_starImage;

@interface TTStarView ()


@end

@implementation TTStarView {

}
@synthesize rating = _rating;
@synthesize starViewSize = _starViewSize;


+ (void)initialize {
    _starImage = [UIImage imageNamed:@"star.png"];
    _starHighlightedImage = [UIImage imageNamed:@"star_highlighted.png"];
}

-(id)initWithOrigin:(CGPoint)origin withSize:(TTStarViewSize)starViewSize{
    self = [super initWithFrame:CGRectMake(origin.x, origin.y, 0, 0)];
    if (self) {
        self.starViewSize = starViewSize;
    }
    return self;
}

#pragma mark - shared init

- (void)sharedInit {
    self.backgroundColor = [UIColor clearColor];
    _starViewSize = TTStarViewSizeTiny;
}

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self sharedInit];
    }
    return self;
}

- (void)awakeFromNib {
    [super awakeFromNib];
    [self sharedInit];
}


#pragma mark licecycle
- (void)dealloc {

}


- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];
    [self setBackgroundColor:[UIColor clearColor]];
    //draw the normal stars..
    int i;
    float x = rect.origin.x;
    float y = rect.origin.y;
    float starScale = _starViewSize / 100.0f;

    float starWidth = kStarWidth * starScale;
    float starHeight = kStarHeight * starScale;
    float gap = kGap * starScale;
    for (i =0; i < _rating; i++){
        [_starHighlightedImage drawInRect:CGRectMake(x, y, starWidth, starHeight)];
        x+= gap + starWidth;
    }
    x = rect.origin.x;

    //draw selected stars
    for (i = (int) _rating; i < kMaxStars; i++){
        [_starImage  drawInRect:CGRectMake(x, y, starWidth, starHeight)];
        x+= gap + starWidth;
    }
}

#pragma mark public api

- (void)setRating:(float)aRating {
    _rating = aRating;
    [self setNeedsDisplay];
}


- (void)setStarViewSize:(TTStarViewSize)aStarViewSize {
    _starViewSize = aStarViewSize;
    float starScale = aStarViewSize / 100.0f;
    self.frame = CGRectMake(self.x, self.y, ((kStarWidth + kGap) * kMaxStars) *starScale, (kStarHeight) * starScale);
    [self setNeedsLayout];

}


@end