Round specific corners of and show shadow on specific sides only

Question

I have the following piece of code to round only specific corners of a view:

- (void)roundOnlySpecifiedCornersInView:(UIView *)view corners:(UIRectCorner)corners
{
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds byRoundingCorners:(corners) cornerRadii:CGSizeMake(4.0, 4.0)];
    CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];

    maskLayer.path  = maskPath.CGPath;
    view.layer.mask = maskLayer;
}

This works perfectly in isolation. Now I also want shadow in my view, but I specifically want to apply shadow in different cases:

on all sides
all sides except bottom
all sides except top
left/right sides only

All techniques I encountered work by creating an inset of the view. The problem with this, is that, say you want to only keep shadow on left/right sides, you offset bottom and top. Since the Rect is now less high, the shadow at the left and right does not cover the full height of the view. Also, the mask layer used for rounding corners causes the shadow to no longer appear.

Example code for this:

    innerView.layer.shadowColor = [[UIColor colorWithWhite:0.0f alpha:0.1f] CGColor];
    innerView.layer.shadowOpacity = 1.0f;
    innerView.layer.shadowOffset = CGSizeMake(0.0f, 0.0f);
    innerView.layer.shadowRadius = 6.0f;

    CGRect shadowFrame = UIEdgeInsetsInsetRect(innerView.bounds, UIEdgeInsetsMake(9, 0, 9, 0));
    CGPathRef shadowPath = [UIBezierPath bezierPathWithRect:shadowFrame].CGPath;

    innerView.layer.shadowPath = shadowPath;

How can I round specific corners in a view and at the same time show shadow only at specified sides?

Answers in Swift are appreciated too!

Screenshot of what I want (this one is easy since all corners need to be rounded so I can use .layer.cornerRadius and it has shadow at all sides):

Now I just want to round only 2 of the corners (top left and top right, bottom left and bottom right) and add shadow to only some sides.

http://stackoverflow.com/questions/22679886/how-to-make-a-uiview-with-optional-rounded-corners-and-border/22680538#22680538 — Kirit Modi, May 14 '16 at 04:03
@KiritModi you are referring to the exact same code I already have for rounding corners. — edwardmp, May 14 '16 at 13:34

KudoCC · Accepted Answer · 2016-05-16T02:46:14.243

I'm not sure if it meet your demand. The code create an image with top and bottom shadow, and all rounding corner, you can modify the code to achieve what you need. You can use the image as the background of your cell(It's seems that it is UITableViewCell)

Let me know if it don't work for you.

The image:

// create a shadow image
CGSize size = CGSizeMake(ScreenWidth, ScreenWidth);
UIGraphicsBeginImageContextWithOptions(size, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();

UIColor *backgroundColor = [UIColor colorWithRed:246.0/255.0 green:246.0/255.0 blue:246.0/255.0 alpha:1.0];
UIColor *fillColor = [UIColor whiteColor];
CGRect rect = CGRectMake(10, 10, 100, 44);

// re-draw the background
CGContextSetFillColorWithColor(context, backgroundColor.CGColor);
CGContextFillRect(context, CGRectMake(0, 0, size.width, size.height));

// set top and bottom shadow
CGRect rectTop = CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, 5);
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(0, -5), 5, [UIColor colorWithRed:0 green:0 blue:0 alpha:0.1].CGColor);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextFillRect(context, rectTop);
CGContextRestoreGState(context);

CGRect rectBottom = CGRectMake(rect.origin.x, rect.origin.y+rect.size.height-5, rect.size.width, 5);
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(0, 5), 5, [UIColor colorWithRed:0 green:0 blue:0 alpha:0.1].CGColor);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextFillRect(context, rectBottom);
CGContextRestoreGState(context);

// re-draw the background
CGContextSetFillColorWithColor(context, backgroundColor.CGColor);
CGContextFillRect(context, rect);

CGContextSaveGState(context);
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(4.0, 4.0)];
[maskPath addClip];
CGContextSetFillColorWithColor(context, fillColor.CGColor);
CGContextFillRect(context, rect);
CGContextRestoreGState(context);

You can modify the code to get a top left shadow:

// create a shadow image
CGSize size = CGSizeMake(ScreenWidth, ScreenWidth);
UIGraphicsBeginImageContextWithOptions(size, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();

UIColor *backgroundColor = [UIColor colorWithRed:246.0/255.0 green:246.0/255.0 blue:246.0/255.0 alpha:1.0];
UIColor *fillColor = [UIColor whiteColor];
CGRect rect = CGRectMake(10, 10, 100, 44);

// re-draw the background
CGContextSetFillColorWithColor(context, backgroundColor.CGColor);
CGContextFillRect(context, CGRectMake(0, 0, size.width, size.height));

// set top and left shadow
CGRect rectTop = CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, 5);
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(0, -5), 5, [UIColor colorWithRed:0 green:0 blue:0 alpha:0.1].CGColor);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextFillRect(context, rectTop);
CGContextRestoreGState(context);

CGRect rectLeft = CGRectMake(rect.origin.x, rect.origin.y, 5, rect.size.height);
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(-5, 0), 5, [UIColor colorWithRed:0 green:0 blue:0 alpha:0.1].CGColor);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextFillRect(context, rectLeft);
CGContextRestoreGState(context);

// re-draw the background
CGContextSetFillColorWithColor(context, backgroundColor.CGColor);
CGContextFillRect(context, rect);

CGContextSaveGState(context);
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(4.0, 4.0)];
[maskPath addClip];
CGContextSetFillColorWithColor(context, fillColor.CGColor);
CGContextFillRect(context, rect);
CGContextRestoreGState(context);

HTH

Thanks for your answer. For the shadows, I only miss adding shadow to just left and right but I think I can derive it from your answers. — edwardmp, May 22 '16 at 23:10

score 2 · Answer 2 · answered May 22 '16 at 12:06

In many, many cases you would want to achieve this with drawing the shadow, of course. However, you may consider the following approach: using a stretchable image with the shadow just on the sides that you need, e.g. something similar to (this one has shadow on all sides though):

Just before you say: "Ewwwww! He's using an image for a simple shadow!" let me emphasise that this will work much better in terms of performance. For instance, if you have a lot of cells in a UICollectionView and each one is re-drawing its shadow it could significantly slow down your app during scrolling, whereas with an image-based shadow it's going to be essentially the same.

I would go even further and suggest that you could actually use a stretchable image for masking the view with rounded corners, too! Now, this may look like going a bit too far, but if you notice a drastic decrease in performance I would give it a shot. What you essentially need to do is prepare another stretchable image with a transparent "middle" part and rounded corners of the same colour as your background. Something like:

And again, before you downvote this bizarre way of doing something that can be easily achieved with two lines of code...

view.layer.cornerRadius = 20
view.layer.masksToBounds = true

...Let me point out that this will work ridiculously faster in cases when you have to display a bunch of those masked views simultaneously: for instance, masking UICollectionViewCells. Basically, if you set a mask on a UIView's layer, this mask is going to be re-calculated and applied in real time, which would cost you a lot in terms of performance during frequent redrawing of the UIView contents — when scrolling a UITableView or UICollectionView, for example.

Obviously this wouldn't work if your background is not of a solid colour, and has a gradient for instance. However, in many other cases this may help you achieve much smoother UI performance. Another advantage in your particular case is that you can easily control which corners to mask and where the shadow should drop.

Again, I'm not implying that this is the way to go in each and every case. What I'm saying is that there are a lot of cases when this could help increase the performance significantly: for example, if you are masking far too many views that are rendered on the screen at the same time, and the layout is expected to be redrawn frequently.

score -2 · Answer 3 · edited May 23 '17 at 11:54

-2

for specific corner set corner radius

refer from : how to set cornerRadius for only top-left and top-right corner of a UIView?

UIBezierPath *maskPath;
maskPath = [UIBezierPathbezierPathWithRoundedRect:_backgroundImageView.bounds 
                             byRoundingCorners:(UIRectCornerBottomLeft|UIRectCornerBottomRight) 
                                   cornerRadii:CGSizeMake(3.0, 3.0)];

CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
maskLayer.frame = self.bounds;
maskLayer.path = maskPath.CGPath;
_imageView.layer.mask = maskLayer;
[maskLayer release];

edited May 23 '17 at 11:54

Community

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answered May 19 '16 at 06:49

Chirag Kalsariya

266
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Your code is practically the same as the code I gave in my opening post (same block) – edwardmp May 19 '16 at 12:04

Round specific corners of and show shadow on specific sides only

3 Answers3