Rounded UIView using CALayers - only some corners - How?

Question

Hello ! every one.

In my application - there are four buttons named as follows.

• Top - left
• Bottom - left
• Top - right
• Bottom - right

Above this buttons there is an image view / or we can use also UIView.

Now, suppose user taps on - top - left button. Above image / view should be rounded from that particular corner.

I am having some difficulty in applying rounded corners to the UIView.

Right now I am using following code to apply the rounded corners to each corner of view. Here it is.

    // imgVUserImg is a image view on IB.
    imgVUserImg.image=[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"any Url Here"];
    CALayer *l = [imgVUserImg layer];
    [l setMasksToBounds:YES];
    [l setCornerRadius:5.0];  
    [l setBorderWidth:2.0];
    [l setBorderColor:[[UIColor darkGrayColor] CGColor]];

Above code is applying the roundness to each of corners of supplied View. Instead I just wanted to apply roundness to selected corners like - top / top+left / bottom+right etc.

Is it possible ? IF yes then, How?

Thanks in advance for sharing your knowledge.

Sagar.

Answer 1

This may be too much for you project but I would really recommend using the Three20 library for this type of procedure - it makes things like this so easy.

You can find more about TTStyle and applying it to a view on Three20 Styles page.

Configuring Three20 for your project is quite easy - you can even add scripts to create new Three20 projects.

I would really recommend that you download Three20 and try out the TTCatalog project and look at the View Styles example - you might even stretch what you want to do at the moment and really make it look nice.

Good luck

Answer 2

See this related question. You'll have to draw your own rectangle to a CGPath with some rounded corners, add the CGPath to your CGContext and then clip to it using CGContextClip.

You can also draw the rounded rect with alpha values to an image and then use that image to create a new layer which you set as your layer's mask property (see Apple's documentation).

Answer 3

I used the answer over at How do I create a round cornered UILabel on the iPhone? and the code from How is a rounded rect view with transparency done on iphone? to make this code.

Then I realized I'd answered the wrong question (gave a rounded UILabel instead of UIImage) so I used this code to change it:

http://discussions.apple.com/thread.jspa?threadID=1683876

Make an iPhone project with the View template. In the view controller, add this:

- (void)viewDidLoad
{
    CGRect rect = CGRectMake(10, 10, 200, 100);
    MyView *myView = [[MyView alloc] initWithFrame:rect];
    [self.view addSubview:myView];
    [super viewDidLoad];
}

MyView is just a UIImageView subclass:

@interface MyView : UIImageView
{
}

I'd never used graphics contexts before, but I managed to hobble together this code. It's missing the code for two of the corners. If you read the code, you can see how I implemented this (by deleting some of the CGContextAddArc calls, and deleting some of the radius values in the code. The code for all corners is there, so use that as a starting point and delete the parts that create corners you don't need. Note that you can make rectangles with 2 or 3 rounded corners too if you want.

The code's not perfect, but I'm sure you can tidy it up a little bit.

static void addRoundedRectToPath(CGContextRef context, CGRect rect, float radius, int roundedCornerPosition)
{

    // all corners rounded
    //  CGContextMoveToPoint(context, rect.origin.x, rect.origin.y + radius);
    //  CGContextAddLineToPoint(context, rect.origin.x, rect.origin.y + rect.size.height - radius);
    //  CGContextAddArc(context, rect.origin.x + radius, rect.origin.y + rect.size.height - radius, 
    //                  radius, M_PI / 4, M_PI / 2, 1);
    //  CGContextAddLineToPoint(context, rect.origin.x + rect.size.width - radius, 
    //                          rect.origin.y + rect.size.height);
    //  CGContextAddArc(context, rect.origin.x + rect.size.width - radius, 
    //                  rect.origin.y + rect.size.height - radius, radius, M_PI / 2, 0.0f, 1);
    //  CGContextAddLineToPoint(context, rect.origin.x + rect.size.width, rect.origin.y + radius);
    //  CGContextAddArc(context, rect.origin.x + rect.size.width - radius, rect.origin.y + radius, 
    //                  radius, 0.0f, -M_PI / 2, 1);
    //  CGContextAddLineToPoint(context, rect.origin.x + radius, rect.origin.y);
    //  CGContextAddArc(context, rect.origin.x + radius, rect.origin.y + radius, radius, 
    //                  -M_PI / 2, M_PI, 1);

    // top left
    if (roundedCornerPosition == 1) {
        CGContextMoveToPoint(context, rect.origin.x, rect.origin.y + radius);
        CGContextAddLineToPoint(context, rect.origin.x, rect.origin.y + rect.size.height - radius);
        CGContextAddArc(context, rect.origin.x + radius, rect.origin.y + rect.size.height - radius, 
                        radius, M_PI / 4, M_PI / 2, 1);
        CGContextAddLineToPoint(context, rect.origin.x + rect.size.width, 
                                rect.origin.y + rect.size.height);
        CGContextAddLineToPoint(context, rect.origin.x + rect.size.width, rect.origin.y);
        CGContextAddLineToPoint(context, rect.origin.x, rect.origin.y);
    }   

    // bottom left
    if (roundedCornerPosition == 2) {
        CGContextMoveToPoint(context, rect.origin.x, rect.origin.y);
        CGContextAddLineToPoint(context, rect.origin.x, rect.origin.y + rect.size.height);
        CGContextAddLineToPoint(context, rect.origin.x + rect.size.width, 
                                rect.origin.y + rect.size.height);
        CGContextAddLineToPoint(context, rect.origin.x + rect.size.width, rect.origin.y);
        CGContextAddLineToPoint(context, rect.origin.x + radius, rect.origin.y);
        CGContextAddArc(context, rect.origin.x + radius, rect.origin.y + radius, radius, 
                        -M_PI / 2, M_PI, 1);
    }

    // add the other corners here


    CGContextClosePath(context);
    CGContextRestoreGState(context);
}


-(UIImage *)setImage
{
    UIImage *img = [UIImage imageNamed:@"my_image.png"];
    int w = img.size.width;
    int h = img.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, 50, 1);
    CGContextClosePath(context);
    CGContextClip(context);

    CGContextDrawImage(context, rect, img.CGImage);

    CGImageRef imageMasked = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    [img release];

    return [UIImage imageWithCGImage:imageMasked];
}

Don't forget that you'll need to get the QuartzCore framework in there for this to work.