Question

I’ve created a custom progress bar which subclass UIView and implements drawRect. I manage to draw a single gradient on the entire view. I’d like however to draw several different gradients, each one in a different position. How to I limit CGContextDrawLinearGradient to smaller rect inside my view?

glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);
CGPoint topCenter = CGPointMake(start + (CGRectGetMidX(currentBounds)/currentBounds.size.width), 0.0f);`
        CGPoint midCenter = CGPointMake(start + (CGRectGetMidX(currentBounds)/currentBounds.size.width), currentBounds.size.height);
        CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);
        start = start + (values[i] / currentBounds.size.width);
        CGGradientRelease(glossGradient);
    }

Answer 1

You can use CGContectClipToRect to restrict the drawing area

Then for each gradient do:

CGContextSaveGState(currentContext);
CGContextClipToRect(theRect); // theRect should be the area where you want to draw the gradient
... // gradient drawing code
CGContextRestoreGState(currentContext);