Transparent Context in IOS? - ios

Question

I'm displaying an image in a UIScrollView but I want it to blend with a UIImageView which is laid behind the UIScrollView.
I'm currently trying to override - (void)drawRect:(CGRect)rect in a subclass of UIView created to display the image inside the scrollview, using either the method drawInRect:blendMode:alpha: or CGContextSetBlendMode but none worked. I think the reason is that the current context is opaque but I cannot find a workaround.

Answer 1

You can add UIImageView as a subclass of UIView (parent view of your scroll view).
You can change opacity of your UIImageView to match your criteria. If you just want a image as a background of your UIView you can set up background of your view and as a colour you can use [UIColor colorWithPatternImage:Your UIImage here].
Is it something you need?
//EXTENDED
I try it and both of the example below set the image as a background and when I scroll the image is not moving:
Example 1:
[self.view setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:#"newtons_cradle.jpg"]]];
UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
[scrollView setContentSize:CGSizeMake(self.view.bounds.size.width, 1000.0f)];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 50, 300, 50)];
[label setBackgroundColor:[UIColor whiteColor]];
[label setText:#"Label Test Text"];
[scrollView addSubview:label];
[self.view addSubview:scrollView];
Example 2:
UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
[imageView setImage:[UIImage imageNamed:#"newtons_cradle.jpg"]];
[self.view addSubview:imageView];
UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
[scrollView setContentSize:CGSizeMake(self.view.bounds.size.width, 1000.0f)];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 50, 300, 50)];
[label setBackgroundColor:[UIColor whiteColor]];
[label setText:#"Label Test Text"];
[scrollView addSubview:label];
[self.view addSubview:scrollView]
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