How to Resize Image While Uploading in Asp.net C#

Here’s the code for resizing an image in Asp.net C# while uploading:

 Firstly, we are going to add the following namespaces in our Webform (Asp.net Web Application)

System.Drawing;
System.Drawing.Drawing2D

<asp:fileupload id=”File1″ runat=”server”>
</asp:fileupload>
<asp:button id=”Button1″ onclick=”Button1_Click” runat=”server” text=”Save”>
<asp:label id=”lblmsg” runat=”server” text=””></asp:label>
</asp:button>

Code behind: Code to save and resize image uploaded.

Boom !! This is the masterpiece code.

Here's in the below-given code we have a  method which has two parameters, retrieve as image and height, after retrieving image and height based on its ratio the image gets resized.

Run this code and you will see whenever the user uploads an image then our masterpiece C# code will resize the image to the appropriate size by setting its height or weight. Also, note we are going to maintain the image ratio

public static System.Drawing.Image ScaleImage(System.Drawing.Image image, int maxHeight)
    {
        var ratio = (double)maxHeight / image.Height;
        var newWidth = (int)(image.Width * ratio);
        var newHeight = (int)(image.Height * ratio);
        var newImage = new Bitmap(newWidth, newHeight);
        using (var g = Graphics.FromImage(newImage))
        {
            g.DrawImage(image, 0, 0, newWidth, newHeight);
        }
        return newImage;
    }

Here's the full Code to save and resize the image, also we have applied some validation i.e only image files get uploaded by checking file extension .png, .gif, .jpeg, also checking image size limit.

You can also check how to Preview Image before upload in Asp.net c# using jQuery if you want the user, to view thumbnail photos on the client-side i.e before uploading to the server.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
public partial class UploadLogo : System.Web.UI.Page
{
    public Size OriginalImageSize { get; set; }        //Store original image size.
    public Size NewImageSize { get; set; }
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        lblmsg.Text="";
        if ((File1.PostedFile != null) && (File1.PostedFile.ContentLength > 0))
        {
            Guid uid = Guid.NewGuid();
            string fn = System.IO.Path.GetFileName(File1.PostedFile.FileName);
            string SaveLocation = Server.MapPath("LogoImages") + "" + uid+fn;
            try
            {
                string fileExtention = File1.PostedFile.ContentType;
                int fileLenght = File1.PostedFile.ContentLength;
                if (fileExtention == "image/png" || fileExtention == "image/jpeg" || fileExtention == "image/x-png")
                {
                   if (fileLenght <= 1048576)
                    {
                        System.Drawing.Bitmap bmpPostedImage = new System.Drawing.Bitmap(File1.PostedFile.InputStream);
                        System.Drawing.Image objImage = ScaleImage(bmpPostedImage, 81);
                        // Saving image in jpeg format
                        objImage.Save(SaveLocation,ImageFormat.Jpeg);
                        lblmsg.Text = "The file has been uploaded.";
                        lblmsg.Style.Add("Color", "Green");
                    }
                    else{
                            lblmsg.Text = "Image size cannot be more then 1 MB.";
                            lblmsg.Style.Add("Color", "Red");
                          }
                }
                else {
                        lblmsg.Text = "Invaild Format!";
                        lblmsg.Style.Add("Color", "Red");
                       }
            }
            catch (Exception ex)
            {
                lblmsg.Text= "Error: " + ex.Message;
                lblmsg.Style.Add("Color", "Red");
            }
        }
    }
}

1. An easy way to upload bulk images in Asp.net c#.
2. Preview Image before uploading it with jQuery in Asp.net.
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