Center a Titanium.UI.ImageView inside a parent Titanium.UI.View similar to a `background-size: cover;` in CSS.

centerImageView.js

/**
 * Center a Titanium.UI.ImageView inside a parent Titanium.UI.View
 *     similar to a `background-size: cover;` in CSS.
 * 
 * Takes 3 parameters: imageRatio, parentView, and imageView
 * 
 * imageRatio:
 *     an object with the ratio or actual dimension of the image to be placed in the ImageView.
 *     e.g. {width: 3, height: 2}
 * 
 * parentView:
 *     an object that defines the container where the ImageView is placed. This sets the boundaries
 *     or clipping size for the ImageView. Can be a View or a simple object.
 *     e.g. {width: 500, height: 500}
 * 
 * imageView:
 *     the ImageView object to be centered in a parent View.
 *     e.g. $.imgViewThumb
 * 
 */
var centerImageView = function(imageRatio, parentView, imageView) {
    var h1, w1, h2, w2, x1, x2;
    
    h1 = parseFloat(parentView.height);
    w1 = parseFloat(parentView.width);
    h2 = parseFloat(imageView.height);
    w2 = parseFloat(imageView.width);

    if (imageRatio.width > imageRatio.height) {
        h2 = h1;
        w2 = (imageRatio.width * h2) / imageRatio.height;
    } else {
        w2 = w1;
        h2 = (imageRatio.height * w2) / imageRatio.width;
    }
    x1 = -((w2 * 0.5) - (w1 * 0.5));
    x2 = -((h2 * 0.5) - (h1 * 0.5));

    imageView.height = h2;
    imageView.width = w2;
    imageView.left = x1;
    imageView.top = x2;
};