Redimensionar imágenes manteniendo el ratio para un máximo ancho y alto.

gistfile1.js

var redimensionar = function(srcWidth, srcHeight, maxWidth, maxHeight) {
    var ratio = [maxWidth / srcWidth, maxHeight / srcHeight ];
    ratio = Math.min(ratio[0], ratio[1]);
    
    // Mantener el ancho y alto normal?
    if(ratio < 1){
      srcWidth  = srcWidth*ratio;
	    srcHeight = srcHeight*ratio;	
    }
    
    return { width:srcWidth*ratio, height :srcHeight*ratio };
 }