iPhone SDK - UIImageView: position of image

Question

I have a standard UIImageView with its ContentMode set to UIContentModeAspectRatioFit. I am trying to find out how to get the position of the image relative to either the absolute coordinates or the UIImageView origin.

Is this possible? I have seen lots of posts about how it's not possible to set the position, but nothing on whether or not it's possible to GET the position.

Many thanks, Brett

Answer 1

I know this has been answered, but I wrote a function to calculate the frame of an image inside an imageView in respect to the imageView.

Edit: forgot the most important ones.

+ (CGRect) imagePositionInImageView:(UIImageView*)imageView
{
    float x = 0.0f;
    float y = 0.0f;
    float w = 0.0f;
    float h = 0.0f;
    CGFloat ratio = 0.0f;
    CGFloat horizontalRatio = imageView.frame.size.width / imageView.image.size.width;
    CGFloat verticalRatio = imageView.frame.size.height / imageView.image.size.height;

    switch (imageView.contentMode) {
        case UIViewContentModeScaleToFill:
            w = imageView.frame.size.width;
            h = imageView.frame.size.height;
            break;
        case UIViewContentModeScaleAspectFit:
            // contents scaled to fit with fixed aspect. remainder is transparent
            ratio = MIN(horizontalRatio, verticalRatio);
            w = imageView.image.size.width*ratio;
            h = imageView.image.size.height*ratio;
            x = (horizontalRatio == ratio ? 0 : ((imageView.frame.size.width - w)/2));
            y = (verticalRatio == ratio ? 0 : ((imageView.frame.size.height - h)/2));
            break;
        case UIViewContentModeScaleAspectFill:
            // contents scaled to fill with fixed aspect. some portion of content may be clipped.
            ratio = MAX(horizontalRatio, verticalRatio);
            w = imageView.image.size.width*ratio;
            h = imageView.image.size.height*ratio;
            x = (horizontalRatio == ratio ? 0 : ((imageView.frame.size.width - w)/2));
            y = (verticalRatio == ratio ? 0 : ((imageView.frame.size.height - h)/2));
            break;
        case UIViewContentModeCenter:
            // contents remain same size. positioned adjusted.
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            x = (imageView.frame.size.width - w)/2;
            y = (imageView.frame.size.height - h)/2;
            break;
        case UIViewContentModeTop:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            x = (imageView.frame.size.width - w)/2;
            break;
        case UIViewContentModeBottom:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            y = (imageView.frame.size.height - h);
            x = (imageView.frame.size.width - w)/2;
            break;
        case UIViewContentModeLeft:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            y = (imageView.frame.size.height - h)/2;
            break;
        case UIViewContentModeRight:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            y = (imageView.frame.size.height - h)/2;
            x = (imageView.frame.size.width - w);
            break;
        case UIViewContentModeTopLeft:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            break;
        case UIViewContentModeTopRight:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            x = (imageView.frame.size.width - w);
            break;
        case UIViewContentModeBottomLeft:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            y = (imageView.frame.size.height - h);
            break;
        case UIViewContentModeBottomRight:
            w = imageView.image.size.width;
            h = imageView.image.size.height;
            y = (imageView.frame.size.height - h);
            x = (imageView.frame.size.width - w);
        default:
            break;
    }
    return CGRectMake(x, y, w, h);
}

Answer 2

OK, so I figured it out with a bit of a hack.

I used Trevor Harmon's image resizedImageWithContentMode function to resize the image to the size of the UIImageView. Then I kept the image size and did away with the image (I only need the size, not the image itself). Followed with some simple math, and we have the position of the image in the frame!

    CGSize imageInViewSize = [photo resizedImageWithContentMode:UIViewContentModeScaleAspectFit bounds:imageView.size interpolationQuality:kCGInterpolationNone].size;


    CGRect overlayRect = CGRectMake((imageView.frame.size.width - imageInViewSize.width) / 2,
                                        (imageView.frame.size.height - imageInViewSize.height) / 2, 
                                        imageInViewSize.width, 
                                        imageInViewSize.height);

    NSLog(@"Frame of Image inside UIImageView: Left:%f Top:%f Width:%f Height:%f \n", overlayRect.origin.x, overlayRect.origin.y, overlayRect.size.width, overlayRect.size.height);

FYI: Trevor Harmon's code is at: http://vocaro.com/trevor/blog/