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Posted 23 Feb 2006

Image Resizing Maintaining Height/Width Ratio

, 24 Feb 2006 CPOL
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This article explains how to dynamically resize an image in your web page to a given size, maintaining the original height/width ratio.


This article explains how to dynamically resize an image in your web page to a given size, maintaining the original height/width ratio. If you have a fixed area where to put an image of an unknown size, you can resize the image to respect the desired width and height limits without stretching it.

Source code

You can download the source code, which contains a simple ASPX web page with three controls: two textboxes, where you can set the maximum width and height of the image, and a button that starts image loading. When you click the button, the page loads the given image (the one included is 450x45 pixels, you can change it programmatically) and resizes it to respect the given limits without stretching it.

The main function of the page is the following:

string COMMONFUNCTIONS_IMAGES_RESIZE_TO_TAG(System.Drawing.Image img, 
                       int MaxWidth, int MaxHeight)
    if (img.Width > MaxWidth || img.Height > MaxHeight)
        double widthRatio = (double) img.Width / (double) MaxWidth;
        double heightRatio = (double) img.Height / (double) MaxHeight;
        double ratio = Math.Max(widthRatio, heightRatio);
        int newWidth = (int) (img.Width / ratio);
        int newHeight = (int) (img.Height / ratio);
        return " width=\"" + newWidth.ToString() + "\"" + 
               " height=\"" + newHeight.ToString() + "\" ";
        return "";

This function has the following parameters:

  • img: the System.Drawing.Image to resize.
  • MaxWidth: the maximum width (taken from the textbox).
  • MaxHeight: the maximum height (taken from the textbox).

It returns a string in the following format: " width="100" height="50" ".

You can put this piece of code where useful, for example, in an img tag.

How to run the app

Unzip and run the .aspx file using IIS, or another web server like Cassini or WebMatrix.

Feel free to use this code in your web pages.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Emanuele Briano
Web Developer
Italy Italy
My name is Emanuele Briano, I am 23 years old. I'm an Industrial and Management Engineer from Italy.
I have expertize in: optimization of complex systems, production flow optimization, linear programming, statistical methods, simulation, design of experiments, business management.
I also operate in web consulting and web design. I realise professional web pages, static or dynamic (usually in ASP.NET), from a design based on usability to realisation and online marketing.
My Web Site (english) is
My Web Site (Italian) is

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Comments and Discussions

GeneralNeed code to resize Image Pin
valapdasiSandhya28-Oct-09 20:29
membervalapdasiSandhya28-Oct-09 20:29 
AnswerUse this server-side resizing module instead. This code just changes the image attributes. [modified] Pin
Nathanael Jones6-Aug-08 11:30
memberNathanael Jones6-Aug-08 11:30 
Generalthanx Pin
Zubair Alam23-Aug-07 21:34
memberZubair Alam23-Aug-07 21:34 
GeneralDoesn't resize the image - just changes attributes Pin
Kreyten14-Jun-07 16:41
memberKreyten14-Jun-07 16:41 
Generalexcelent article Pin
autumnEND1-Feb-07 15:49
memberautumnEND1-Feb-07 15:49 
GeneralNot working Pin
fhirzall22-Sep-06 4:41
memberfhirzall22-Sep-06 4:41 

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Article Copyright 2006 by Emanuele Briano
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