Modern technique of adding gradient to UIView

Question

I know of several ways of adding background gradients to UIView. I was wondering what is the most efficient and scalable way of doing so, and why? Here are the techniques I've used:

Create subview of UIView and overwrite the drawRect, where I draw the gradient in current context.

a. When using the above gradient create it with the bounds of view I want to decorate and insert this background gradient as first subview, i.e. – insertSubview:atIndex:

b. After I get the background gradient view from above, I render it in image context and use it as background image, i.e.
```
UIGraphicsBeginImageContext(gradView.bounds.size);
[gradView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *gradientImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIColor *background = [UIColor colorWithPatternImage:gradientImg];
self.view.backgroundColor = background;
```

Create stretchable PNG and use that to decorate view background. Technique is very similar to the way you decorate UIButton.

-(UIColor *)backgroundColor:(CGRect)frame
{
    UIImage *bg = [UIImage imageNamed:@"background_23x36"];
    bg = [bg resizableImageWithCapInsets:UIEdgeInsetsMake(0.0, 11.0, 0.0, 11.0)];
    UIGraphicsBeginImageContextWithOptions(frame.size, YES, [[UIScreen mainScreen] scale]);
    [bg drawInRect:frame];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return [UIColor colorWithPatternImage:image];
}

Create subview of UIView but instead of overwriting the drawRect, use CAGradientLayer. Similar to http://nscookbook.com/2013/04/recipe-20-using-cagradient-layer-in-a-custom-view/

So what is most efficient and scalable way to add gradient as a background?

I'd do it in drawRect of the view. Using CGGradient

Fogmeister
– Fogmeister

2013-04-12 15:09:46 +00:00
Commented Apr 12, 2013 at 15:09 — Fogmeister
– Fogmeister, Commented Apr 12, 2013 at 15:09

jverrijt · Accepted Answer · 2014-04-08 20:29:26Z

9

As Fogmeister suggested above, do it in the drawRect: method of your UIView subclass.

- (void)drawRect:(CGRect)rect
{
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = UIGraphicsGetCurrentContext();

    NSArray *gradientColors = [NSArray arrayWithObjects:(id) [UIColor redColor].CGColor, [UIColor yellowColor].CGColor, nil];

    CGFloat gradientLocations[] = {0, 0.50, 1};
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) gradientColors, gradientLocations);

    CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
    CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));

    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
    CGGradientRelease(gradient);
    CGColorSpaceRelease(colorSpace);
}

edited Apr 8, 2014 at 20:29

answered Apr 12, 2013 at 20:43

jverrijt

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3 Comments

atkabai Over a year ago

I do that in one of the methods above, however after getting gradient view what is more efficient adding it as subview at index 0 or generating color from gradient view image and using that as background color?

jverrijt Over a year ago

You can make any view that needs a gradient background inherit from a UIView class that draws a gradient through its overridden drawRect method. The gradient colors and positions can parameterized if necessary.

Travelling Man Over a year ago

Don't forget to call CGColorSpaceRelease(colorSpace) after you're done with the color space.

Peteee24 · Accepted Answer · 2013-04-12 21:03:32Z

0

DrawRect is the more efficient way i think. I'd like to extend jverrijt's nice answer. If you need alpha components (transparent to black gradient f.e.), then you can use this:

UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, 0.0);
CGContextSaveGState(UIGraphicsGetCurrentContext());
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);
CGContextRestoreGState(UIGraphicsGetCurrentContext());

//Draw stuffs

UIGraphicsEndImageContext();

answered Apr 12, 2013 at 21:03

Peteee24

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