Proportional Image Resize in JavaScript Posted on December 27, 2008 by Dave Fowler

Socialbrowse currently shows summaries of shared links that have an ATOM or RSS feed. The feeds come with images of all sizes and we have to change the height and width to fit within the alloted space. CSS has max-width and max-height parameters but they have issues in IE and they don't keep original proportions of the image! To resize and keep the proportions we use javascript.

This javascript resize function will do a proportional resize to keep the given <img> within the given max height and max width (maxh and maxw). Feel free to copy and use it in any way you like.

var resize = function(img, maxh, maxw) {
  var ratio = maxh/maxw;
  if (img.height/img.width > ratio){
     // height is the problem
    if (img.height > maxh){
      img.width = Math.round(img.width*(maxh/img.height));
      img.height = maxh;
  } else {
    // width is the problem
    if (img.width > maxh){
      img.height = Math.round(img.height*(maxw/img.width));
      img.width = maxw;