adjust image size

image-resize.js

// Call this function *after* the page is completely loaded!
function resize_images(maxht, maxwt, minht, minwt) {
  var imgs = document.getElementsByTagName('img');

  var resize_image = function(img, newht, newwt) {
    img.height = newht;
    img.width  = newwt;
  };
  
  for (var i = 0; i < imgs.length; i++) {
    var img = imgs[i];
    if (img.height > maxht || img.width > maxwt) {
      // Use Ratios to constraint proportions.
      var old_ratio = img.height / img.width;
      var min_ratio = minht / minwt;
      // If it can scale perfectly.
      if (old_ratio === min_ratio) {
        resize_image(img, minht, minwt);
      } 
      else {
        var newdim = [img.height, img.width];
        newdim[0] = minht;  // Sort out the height first
        // ratio = ht / wt => wt = ht / ratio.
        newdim[1] = newdim[0] / old_ratio;
        // Do we still have to sort out the width?
        if (newdim[1] > maxwt) {
          newdim[1] = minwt;
          newdim[0] = newdim[1] * old_ratio;
        }
        resize_image(img, newdim[0], newdim[1]);
      }
    }
  }
}