Converting Uiimageview Touch Coordinates to Uiimage Coordinates

Converting UIImageView Touch Coordinates to UIImage Coordinates

Something like this should get you going.

CGPoint imageViewPoint = [touch locationInView:imageView];

float percentX = imageViewPoint.x / imageView.frame.size.width;
float percentY = imageViewPoint.y / imageView.frame.size.height;

CGPoint imagePoint = CGPointMake(image.size.width * percentX, image.size.height * percentY);

Assuming the UIImageView is called imageView the UITouch is called touch and the UIImage is called image.

How to get the coordinates of point tapped on an UIImageView so that they are at the same position on all the devices (of different size/resolutions)?

I have make same as you want.Can you please try this one. it will help you.

• When you click on UIImageView at that time i have find touch point of the UIImageView.You have to need calculate the percentage of UIImageView base on height and width, so it will work on all device.

//Your imageView add tapGestureRecognizer event

  imageView.isUserInteractionEnabled = true
  let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(tapAction))
  self.imageView.addGestureRecognizer(tapGestureRecognizer)

 @objc func tapAction(sender: UITapGestureRecognizer) {

      let touchPoint = sender.location(in: self.imageView)
      print(touchPoint)

      var z1 = touchPoint.x
      var z2 = touchPoint.y
      print("Before Alert Touched point (\(self.z1), \(self.z2)")

      //convert point into Percentage
      let z1per =  z1 * 100 / self.imageView.frame.size.width
      let z2per =  z2 * 100 / self.imageView.frame.size.height

      print("After Alert Touched point (\(self.z1per), \(self.z2per)")

  //whatever you want to add like button or image on tap action.

    let btn = UIButton(frame: CGRect(x: touchPoint.x - 15, y: touchPoint.y - 15, width: 30, height: 30))
    btn.layer.cornerRadius = 15
    btn image = UIImage(named: "marker.png") as UIImage?
    btn.setImage(image, for: .normal)
    self.imageView.addSubview(btn)
}

How to determine location of (x, y) user tapped on a UIImage not UIImageView?

Yes, by adding a UITapGestureRecognizer to the image view, getting the tap position from that and converting the tap coordinates to the image coordinates:

let img = UIImage(named: "whatever")

// add a tap recognizer to the image view
let tap = UITapGestureRecognizer(target: self, 
             action: #selector(self.tapGesture(_:)))
imgView.addGestureRecognizer(tap)
imgView.isUserInteractionEnabled = true
imgView.image = img
imgView.contentMode = .scaledAspectFit

func convertTapToImg(_ point: CGPoint) -> CGPoint? {
    let xRatio = imgView.frame.width / img.size.width
    let yRatio = imgView.frame.height / img.size.height
    let ratio = min(xRatio, yRatio)

    let imgWidth = img.size.width * ratio
    let imgHeight = img.size.height * ratio

    var tap = point
    var borderWidth: CGFloat = 0
    var borderHeight: CGFloat = 0
    // detect border
    if ratio == yRatio {
        // border is left and right
        borderWidth = (imgView.frame.size.width - imgWidth) / 2
        if point.x < borderWidth || point.x > borderWidth + imgWidth {
            return nil
        }
        tap.x -= borderWidth
    } else {
        // border is top and bottom
        borderHeight = (imgView.frame.size.height - imgHeight) / 2
        if point.y < borderHeight || point.y > borderHeight + imgHeight {
            return nil
        }
        tap.y -= borderHeight
    }

    let xScale = tap.x / (imgView.frame.width - 2 * borderWidth)
    let yScale = tap.y / (imgView.frame.height - 2 * borderHeight)
    let pixelX = img.size.width * xScale
    let pixelY = img.size.height * yScale
    return CGPoint(x: pixelX, y: pixelY)
}

@objc func tapGesture(_ gesture: UITapGestureRecognizer) {
    let point = gesture.location(in: imgView)
    let imgPoint = convertTapToImg(point)
    print("tap: \(point) -> img \(imgPoint)")
}

Convert points from image to UIImageView points, contentMode-aware

Today, I've had some spare time to put together my solution to this problem and publish it on GitHub: UIImageView-GeometryConversion

It's a category on UIImageView that provides methods for converting points and rects from the image to view coordinates and respects all of the 13 different content modes.

Hope you like it!

How Do I Get the Coordinates of an Animated UIImageView

I was able to finally get the objects to report where they were on screen using the following changes to my touchesBegan method:

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesBegan:touches withEvent:event];

    UITouch *touch = [touches anyObject];
    CGPoint startPoint = [touch locationInView:self.view];
    CGFloat x = startPoint.x;
    CGFloat y = startPoint.y;

    //create touch point
    CGPoint touchPoint = CGPointMake(x, y);

    // loop through the items we're iterested in being tapped on here
    for (UIImageView *fish in self.swimmers) {
        CGRect fishFrame = [[fish.layer presentationLayer] frame];

        if (CGRectContainsPoint(fishFrame, touchPoint)) {
            NSLog(@"You hit fish: %u",fish.tag); // do stuff here
        }
    }
}

Return UIImageView to starting coordinates when tapped after zooming in?

Add a UITapGestureRecognizer to the view. When it fires, set view's transform back to CGAffineTransformIdentity.

Finding touch location according to image in UIImageView

Try this code. I did not test it so mistakes might have been made. I hope the comments will help you enough to find the correct solution.

- (CGPoint)point:(CGPoint)point onImageWithSize:(CGSize)imageSize inImageView:(UIImageView *)view contentMode:(UIViewContentMode)mode
{
    // find the relative image position on the view
    CGPoint imageRelativeOrigin = CGPointZero;
    CGSize imageRelativeSize = view.frame.size;

    if(mode == UIViewContentModeScaleAspectFit)
    {
        // we expect one of the origin coordinates has a positive offset
        // compare the ratio
        if(imageSize.width/imageSize.height > view.frame.size.width/view.frame.size.height)
        {
            // in this case the image width is the same as the view width but height is smaller
            imageRelativeSize = CGSizeMake(view.frame.size.width, view.frame.size.width*(imageSize.height/imageSize.width));
            CGFloat verticalOffset = (view.frame.size.height-imageRelativeSize.height)*.5f; // this is the visible image offset
            imageRelativeOrigin = CGPointMake(.0f, verticalOffset);
        }
        else
        {
            // in this case the image height is the same as the view height but widh is smaller
            imageRelativeSize = CGSizeMake(view.frame.size.height*(imageSize.width/imageSize.height), view.frame.size.height);
            CGFloat horizontalOffset = (view.frame.size.width-imageRelativeSize.width)*.5f; // this is the visible image offset
            imageRelativeOrigin = CGPointMake(horizontalOffset, .0f);
        }
    }
    else
    {
        // TODO: add other content modes
    }

    CGPoint relativeImagePoint = CGPointMake(point.x-imageRelativeOrigin.x, point.y-imageRelativeOrigin.y); // note these can now be off the image bounds
    // resize to image coordinate system
    CGPoint actualImagePoint = CGPointMake(relativeImagePoint.x*(imageSize.width/imageRelativeSize.width),
                                           relativeImagePoint.y*(imageSize.height/imageRelativeSize.height));
    return actualImagePoint;
}

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