How do I add a UIImage to grouped UITableViewCell so it rounds the corners?

Question

I\'m trying to add images to table cells in a grouped UITableView but the corners of the images are not clipped. What\'s the best way to go about clipping these (besides clippin

Answer 1

A couple additions/changes, hope it helps someone:

1) roundTop and roundBottom impl changed slightly.

2) made a class method in separate class so reuse is easier, rather than copy/paste everywhere.

First, the new class details:

#import 
#import 

@interface RoundedImages : NSObject {
}
+(UIImage *)roundCornersOfImage:(UIImage *)source roundTop:(BOOL)top roundBottom:(BOOL)bottom;
@end

And its implementation:

#import "RoundedImages.h"

@implementation RoundedImages

void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth, float ovalHeight, BOOL top, BOOL bottom)
{
    float fw, fh;
    if (ovalWidth == 0 || ovalHeight == 0) {
        CGContextAddRect(context, rect);
        return;
    }
    CGContextSaveGState(context);
    CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
    CGContextScaleCTM (context, ovalWidth, ovalHeight);
    fw = CGRectGetWidth (rect) / ovalWidth;
    fh = CGRectGetHeight (rect) / ovalHeight;
    CGContextMoveToPoint(context, fw, fh/2);

    if (top) {
        CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 3);
        CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 3);
        CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 0);
        CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 0);
    } else {
        CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 0);
        CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 0);
        CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 3);
        CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 3);
    }

    CGContextClosePath(context);
    CGContextRestoreGState(context);
}

+(UIImage *)roundCornersOfImage:(UIImage *)source roundTop:(BOOL)top roundBottom:(BOOL)bottom {
    int w = source.size.width;
    int h = source.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);

    CGContextBeginPath(context);
    CGRect rect = CGRectMake(0, 0, w, h);
    //addRoundedRectToPath(context, rect, 4, 4, top, bottom);
    addRoundedRectToPath(context, rect, 5, 5, top, bottom);
    CGContextClosePath(context);
    CGContextClip(context);

    CGContextDrawImage(context, CGRectMake(0, 0, w, h), source.CGImage);

    CGImageRef imageMasked = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    //return [UIImage imageWithCGImage:imageMasked];
    UIImage *image = [UIImage imageWithCGImage:imageMasked]; 
    CGImageRelease(imageMasked);
    return image;
}

@end

To use in another class (eg, view controller):

#import "RoundedImages.h"

...and later we use it like this...

UIImageView *imageView = nil;
    UIImage *img = [UIImage imageNamed:@"panel.png"];

    if (indexPath.row == 0) {
        imageView = [[UIImageView alloc]initWithImage:[RoundedImages roundCornersOfImage:img roundTop:YES roundBottom:NO]];
    }
    else if (indexPath.row == ([choices count]-1))
    {
        imageView = [[UIImageView alloc]initWithImage:[RoundedImages roundCornersOfImage:img roundTop:NO roundBottom:YES]];
    }
    else {
        imageView = [[UIImageView alloc]initWithImage:img];
    }
    cell.backgroundColor = [UIColor clearColor];
    imageView.clipsToBounds = NO;
    cell.backgroundView = imageView;
    cell.backgroundView = [[UIView alloc] initWithFrame:CGRectZero];
    [cell.backgroundView addSubview:imageView];
    [imageView release];

Note that the "choices" above was just a mutable array I was using on this page that contained the data for the tableview.

I should add that the usage snippet above is used inside your cellForRowAtIndexPath method, and "cell" is a uitableviewcell.

Anyway, works like a champ for me.