How to calculate width and height values of an image when resized?

I need a way to calculate the width and height values of an image when resized to 1024px

The largest value of the image, height or width will be resized to 1024px and I need to figure out the remaining width or height value.

An image (3200 x 2400px) converts to (1024 x 768px) when resized.

This needs to be dynamic as some images will be portrait and some landscape.

Can anyone suggest how I'd work a solution into the following:

<msxsl:script language="C#" implements-prefix="emint">
    <![CDATA[public string GetExtension(string fileName)
      { 
      string[] terms = fileName.Split('.');
      if (terms.Length <= 0)
      {
      return string.Empty;
      }
      return terms[terms.Length -1];
      }

      public string GetFileName(string fileName)
      { 
      string[] terms = fileName.Split('/');
      if (terms.Length <= 0)
      {
      return string.Empty;
      }开发者_开发知识库
      return terms[terms.Length -1];
      }

      public string GetFileSize(Decimal mbs)
      { 
      Decimal result = Decimal.Round(mbs, 2);
      if (result == 0)
      {
      result = mbs * 1024;
      return Decimal.Round(result, 2).ToString() + " KB";
      }
      return result.ToString() + " MB";
      } 

      public string GetCentimeters(Decimal pix)
      {
      Decimal formula  = (decimal)0.026458333;
      Decimal result = pix * formula;
      return Decimal.Round(result,0).ToString();
      }]]>
  </msxsl:script>

          width = 1024;
          height = 768;

          ratio_orig = width_orig/height_orig;

          if (width/height > ratio_orig) {
             width = height*ratio_orig;
          } else {
             height = width/ratio_orig;
          }

The values of width and height at the end correspond to the width and height of the image. This maintains the aspect ratio.

Here's an algorithm in pseudocode. It will choose the largest possible size (less than 1024x1024px) that has the same width/height ratio as the original image.

target_width = 1024
target_height = 1024

target_ratio = target_width / target_height
orig_ratio = orig_width / orig_height

if orig_ratio < target_ratio
    # Limited by height
    target_width = round(target_height * orig_ratio)
else
    # Limited by width
    target_height = round(target_width / orig_ratio)