Question

I am trying to apply the same gradient as per the screen shot below using CGGradientCreateWithColorComponents.

This is what I’m using at the moment, however it’s not quite right and I’m after a better way of trying to guess these values. I’d also like to know how to actually determine what these values are as this code was grabbed from a tutorial, which didn’t explain much at all in terms of what the components are.

CGColorSpaceRef myColorspace = CGColorSpaceCreateDeviceRGB();
CGFloat components[8] = { 1, 1, 1, 1, 0.866, 0.866, 0.866, 1 };
CGFloat locations[2] = { 0.0, 1.0 };

CGGradientRef myGradient = CGGradientCreateWithColorComponents(myColorspace, components, locations, 2);

Answer 1

I’ve played around with it and got this picture:

with colors:

static const CGFloat colors [] = { 
0.894, 0.894, 0.894, 1.0, 
0.694, 0.694, 0.694, 1.0
};

using this piece of code:

- (void) drawRect:(CGRect)rect {
   CGColorSpaceRef baseSpace = CGColorSpaceCreateDeviceRGB();
   CGGradientRef gradient = CGGradientCreateWithColorComponents(baseSpace, colors, NULL, 2);
   CGColorSpaceRelease(baseSpace), baseSpace = NULL;

   CGContextRef context = UIGraphicsGetCurrentContext();
   CGContextClearRect(context, rect);
   CGContextSaveGState(context);

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

   CGContextClip(context);
   CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);

   CGGradientRelease(gradient), gradient = NULL;

   CGContextRestoreGState(context);
   [super drawRect:rect];
 }

I dont know if it’s close enough.