Reputation: 221
I am trying to get a transparent background in CG but it keeps coming out black.
I have the following code:
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
DLog(@">>> Alloc: DrawingCanvas [0x%X]", (unsigned int)self);
[self setOpaque:NO];
[self setBackgroundColor:[UIColor clearColor]];
}
return self;
}
- (void) drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect frame = rect;
int counter = 3;
CGContextClearRect(context, frame);
CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
CGContextFillRect(context, frame);
}
How do I get this code to show a transparent background?
Upvotes: 11
Views: 6796
Reputation: 25535
I had this same problem and the solution was to set the backgroundColor
property of the UIView which I was drawing in, from the parent view's class. I didn't need any code to clear the background in the UIView's class where the drawing happens.
myDrawingView.backgroundColor = [UIColor clearColor];
Upvotes: 1
Reputation: 1300
You could simply remove these lines :
CGContextClearRect(context, frame);
CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
CGContextFillRect(context, frame);
As long as you have set opaque to NO and clearColor as backgroundColor everything should be fine.
Be careful when drawing since your other drawing code may fill the background entirely (take care of [path fill]
things in a non-clipped context).
Upvotes: 4
Reputation: 94834
With that setup and as long as you don't set clearsContextBeforeDrawing
to NO, the background should already be transparent when your drawRect:
method is called. Remove the CGContextClearRect and other drawing calls.
Upvotes: 4