CODEWITHSUNDEEP
ios4gradientdrawrect
cboe
cboe

Reputation: 477

CGGradientCreateWithColors not working on iOS 4 anymore

this is the code I use in a UIView subclass to easily add gradient views:

#import "GradientView.h"


@implementation GradientView

@synthesize direction, startColor, endColor;

-(id)initWithFrame:(CGRect)frame startColor:(UIColor *)start_color endColor:(UIColor *)end_color direction:(GradientDirection)gradient_direction
{
  if((self = [super initWithFrame:frame]))
  {
    self.startColor = start_color;
    self.endColor = end_color;
    self.direction = gradient_direction;
  }
  return self;
}

- (id)initWithFrame:(CGRect)frame
{
    [self doesNotRecognizeSelector:_cmd];
  return self;
}

-(void)drawRect:(CGRect)rect
{
  CGColorRef start_color = [self.startColor CGColor];
  CGColorRef end_color = [self.endColor CGColor];

  NSArray *colors = [NSArray arrayWithObjects:(__bridge id)start_color, (__bridge id)end_color, nil];
  CGFloat locations[] = {0,1};
  CGGradientRef gradient = CGGradientCreateWithColors(CGColorGetColorSpace(start_color), (__bridge CFArrayRef)colors, locations);
  CGRect bounds = self.bounds;
  CGPoint start;
  CGPoint end;
  if(direction == GradientLeftToRight)
  {
    start = CGPointMake(bounds.origin.x, CGRectGetMidY(bounds));
    end = CGPointMake(CGRectGetMaxX(bounds), CGRectGetMidY(bounds));
  }
  else
  {
    start = CGPointMake(CGRectGetMidX(bounds), bounds.origin.y);
    end = CGPointMake(CGRectGetMidX(bounds), CGRectGetMaxY(bounds));
  }

  CGContextRef context = UIGraphicsGetCurrentContext();
  CGContextDrawLinearGradient(context, gradient, start, end, 0);
  CGGradientRelease(gradient);
}

@end

It worked flawlessly in earlier xcode versions, but when I run it on iOS4.3 now it's just displaying as black. In iOS 5 it works fine, any suggestions?

Upvotes: 0

Views: 673

Answers (1)

jpap
jpap

Reputation: 964

I had a similar problem when creating a RGBA image context with UIGraphicsBeginImageContextWithOptions(...).

In my case, I was using gradient stops were created with [UIColor colorWithWhite:alpha:]. Worked fine on iOS 5, but not on iOS 4. When I created the gradient stops with [UIColor colorWithRed:green:blue:alpha] (and the same value applied to red, green and blue channels) then it started working on iOS 4.

I suspect it has to do with an incompatible colorspace behind the scenes on iOS 4. Perhaps colorWithWhite:alpha: is using a "Gray" colorspace, that fails to work when the context is in the RGB colorspace.

Upvotes: 3

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