Question

I have a simple application that shows the user an image (in a UIImageView) whereby they touch on a part of the screen and then on the next screen the same image is shown (in a UIImageView) but now has a “signature” overlayed on it. The issue I am having is that it seems that the x,y coordinates returned from the touches do not seem to map properly on the UIImageView on the second screen.

For instance when I touch the bottom of the screen I get: X: 157.000000 Y: 358.000000

but the bottom of the screen should be 480 ? since my screen dimensions are: SCREEN HEIGHT AND WIDTH AT X: 320.000000 Y: 480.000000. This causes the signature to be placed at a DIFFERENT spot than what the user intended.

I use the following code to get my touch coordinates:

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{

    NSLog(@"TOUCH HAPPENED");
    UITouch *touch = [touches anyObject];
    CGPoint touchCoordinates = [touch locationInView:self.view];
    NSLog(@"X: %f   Y: %f",touchCoordinates.x, touchCoordinates.y);

}

I am using the following code to place the “signature” with the values I get from the touch:

CGRect screenRect = [[UIScreen mainScreen] bounds]; 
        UIGraphicsBeginImageContext(screenRect.size);


        [pageImage drawInRect:CGRectMake(0, 0, screenRect.size.width, screenRect.size.height)]; // this is the original image

        NSLog(@"SCREEN HEIGHT AND WIDTH  AT   X: %f   Y: %f",screenRect.size.width, screenRect.size.height);


        NSLog(@"PLACING IT AT TOUCH COORDINATES  X: %f   Y: %f",sigLocation.x, sigLocation.y);
        UIImage *shieldLogo = [UIImage imageNamed:@"shield_bw.gif"];
        [shieldLogo drawInRect:CGRectMake(sigLocation.x, sigLocation.y, shieldLogo.size.width/2, shieldLogo.size.height/2)];
        [theSignature drawAtPoint:CGPointMake(sigLocation.x+24.000000, sigLocation.y) withFont:[UIFont fontWithName:@"Arial" size:8.0]];
        [theSignature2 drawAtPoint:CGPointMake(sigLocation.x+24.000000, sigLocation.y+ 8.000000) withFont:[UIFont fontWithName:@"Arial" size:8.0]];

        UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        [image setImage:resultingImage];

Answer 1

The issue might be with the view that the user is touching. You might try (as seen in this link)

UITouch * touch = [touches anyObject];
CGPoint pos = [touch locationInView: [UIApplication sharedApplication].keyWindow];
NSLog(@"Position of touch: %.3f, %.3f", pos.x, pos.y);

This should give the location of the touch relative to the screen.