Useful class for resize DOM Javascript objects

usizer.js

/*
 name: uSizer
 description: Useful class for resize DOM objects
 license: MIT-Style License <http://joseluisquintana.pe/license.txt>
 copyright: Jose Luis Quintana <http://joseluisquintana.pe/>
 authors: Jose Luis Quintana <joseluisquintana20@gmail.com>
 */
function uSizer(parent, child) {
    this.version = '1.0';
    this.child = null;
    this.parent = null;

    this.initialize = function(parent, child) {
        this.setParent(parent);
        this.setChild(child);
    };

    this.setChild = function(element) {
        this.child = element;
    };

    this.setParent = function(element) {
        this.parent = element;
    };

    this.resizeToHeight = function(height) {
        this.resize(this.getPropWidth(height), height);
    };

    this.resizeToWidth = function(width) {
        this.resize(width, this.getPropHeight(width));
    };

    this.getPropWidth = function(height) {
        return this.child.offsetWidth * (height / this.child.offsetHeight);
    };

    this.getPropHeight = function(width) {
        return this.child.offsetHeight * (width / this.child.offsetWidth);
    };

    this.scale = function(scale) {
        this.resize(this.child.offsetWidth * scale / 100, this.child.offsetHeight * scale / 100);
    };

    this.centerCropResize = function() {
        var width, height, pwidth, pheight;
        if (arguments.length === 2) {
            width = arguments[0];
            height = arguments[1];
        } else {
            width = this.parent.offsetWidth;
            height = this.parent.offsetHeight;
        }

        pwidth = this.getPropWidth(height);
        pheight = this.getPropHeight(width);
        if (pwidth === width && pheight === height) {
            this.resizeToWidth(width);
        } else {
            if (pheight > height) {
                this.resizeToWidth(width);
            } else {
                pheight += height - pheight;
                this.resizeToHeight(pheight);
            }

            this.croper(width, height, (this.child.offsetWidth - width) / 2, (this.child.offsetHeight - height) / 2);
        }
    };

    this.centerCrop = function() {
        var width = this.parent.offsetWidth, height = this.parent.offsetHeight;
        this.croper(width, height, (this.child.offsetWidth - width) / 2, (this.child.offsetHeight - height) / 2);
    };

    this.crop = function(x, y) {
        this.croper(this.parent.offsetWidth, this.parent.offsetHeight, x, y);
    };

    this.croper = function(width, height, x, y) {
        this.resize(width, height, x, y, true);
    };

    this.resize = function(width, height, x, y, crop) {
        if (crop) {
            if (this.parent) {
                this.parent.style.height = height + 'px';
                this.parent.style.width = width + 'px';
            }

            if (this.child) {
                this.child.style.position = 'absolute';
                this.child.style.marginTop = -y + 'px';
                this.child.style.marginLeft = -x + 'px';
            }
        } else {
            if (this.child) {
                this.child.style.height = height + 'px';
                this.child.style.width = width + 'px';
            }
        }
    };

    if (parent && child) {
        this.initialize(parent, child);
    }
}