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

Question

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;
      }
      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>

possible duplicate of [How to "smart resize" a displayed image to original aspect ratio](http://stackoverflow.com/questions/3008772/how-to-smart-resize-a-displayed-image-to-original-aspect-ratio) — PleaseStand, Apr 19 '11 at 02:32

Nick Brunt · Accepted Answer · 2011-04-19T02:00:30.687

2

          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.

edited Apr 19 '11 at 02:00

answered Apr 19 '11 at 01:46

Nick Brunt

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PleaseStand · Answer 2 · 2011-04-19T02:27:37.927

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)

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

2 Answers2