Limiting a pan gesture recognizer to an ImageView? - ios

Question

I have an ImageView containing a circular gradient and a panGestureRecognizer that I want to limit specifically to the gradient to prevent interference with the UISliders in the view or the white background.
How do I only recognize touches within the gradient?
As of now, I am using this equation with bad results :
CGPoint lastPoint = [sender locationOfTouch: sender.numberOfTouches - 1 inView: gradientView];
CGPoint center = CGPointMake((size.width/2), (size.height /2));
These variables are used to indicate the center of the gradient. This is the equation :
if((lastPoint.x - center.x) + (lastPoint.y - center.y)/2 < radius)
{
UIColor *color = [UIColor colorWithHue: angle / (M_PI * 2.0) saturation:saturationSlider.value brightness:hellSlider.value alpha:alphaSlider.value];
if ([color getRed: &r green: &g blue:&b alpha: &a])
{
NSLog(#"Color value - R : %g G : %g : B %g", r*255, g*255, b*255);
}
float red = r;
float green = g;
float blue = b;
rText.text = [NSString stringWithFormat:#"%.0f",rSlider.value];
gText.text = [NSString stringWithFormat:#"%.0f",green*255];
bText.text = [NSString stringWithFormat:#"%.0f",blue*255];
colorView.backgroundColor = [UIColor colorWithRed:(rText.text.floatValue/255) green:(gText.text.floatValue/255) blue:(bText.text.floatValue/255) alpha:alphaSlider.value];
rSlider.value = red*255;
gSlider.value = green*255;
bSlider.value = blue*255;
alphaText.text = [NSString stringWithFormat:#"%.2f",alphaSlider.value];
brightnessText.text = [NSString stringWithFormat:#"%.2f",hellSlider.value];
saturationText.text = [NSString stringWithFormat:#"%.2f",saturationSlider.value];
}
This code above is inside my panGestureRecognizer's method.

Answer 1

You can add another UIView on the top of that circular view and apply gesture to that View.
UIView *gestureView = [[UIView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
[gestureView.layer setCornerRadius:gestureView.frame.size.width/2];
This will give you a circular UIView.
Adjust the size and the position according to your need.