Sagar R. Kothari Sagar R. Kothari - 12 days ago 9
Objective-C Question

Rounded UIView using CALayers - only some corners - How?

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


  • Top - left

  • Bottom - left

  • Top - right

  • Bottom - right



Above the buttons there is an image view (or a UIView).

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

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

Right now I am using the following code to apply the rounded corners to each view:

// 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? How?

Answer

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];
}

alt text

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

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