How to resize image in Asp.net?

Introduction: In this article i will explain with example How to upload image file through file upload control and resize the uploaded image in asp.net using both C#.Net and VB.Net languages.In previous articles i explained How to create thumbnail, small and large version of the uploaded image in Asp.net and How to Validate and upload image files in asp.net and jQuery to validate file extension and upload image file and Bind,upload,download,delete image files from the GridView  and Drag & drop to upload multiple files using AjaxFileUpload like Facebook and Upload and create Zip file and Maintain image on PostBack in FileUpload control. 


Description: While working on asp.net application it is sometimes required to resize the image as per application requirement. Suppose there is image upload functionality in your website where user can upload their pictures. In this case you must resize the image before storing so that web space requirement for storing can be reduced.

Implementation: Let's understand by creating a demo website.

Source Code:

• In the design page (.aspx) place a FileUpload Control and a Button control as:

<table>

        <tr>

                <td>

                    <asp:FileUpload ID="FileUpload1" runat="server" />

                </td>

            </tr>

            <tr>

                <td>

                      <asp:Button ID="btnUpload" runat="server" Text="Submit"

            onclick="btnUpload_Click" /></td>

         </tr>          

  </table>

C#.NET Code to  upload and resize the images

• In the code behind file (.aspx.cs) write the code as:

First include following namespaces:

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

using System.Drawing.Design;

using System.IO;

• Then write the code as:

protected void btnUpload_Click(object sender, EventArgs e)

    {

        if (FileUpload1.HasFile)

        {

            string img=string.Empty;

            Bitmap bmpImg=null;

            try

            {

                bmpImg = Resize_Image(FileUpload1.PostedFile.InputStream, 210, 130);

                img = Server.MapPath("images/") + Guid.NewGuid().ToString() + “.png";

                bmpImg.Save(img, ImageFormat.Jpeg);

            }

            catch (Exception ex)

            {

                Response.Write("Error occured: " + ex.Message.ToString());

            }

            finally

            {

                img = string.Empty;

                bmpImg.Dispose();

            }      

          }

    }

  

private Bitmap Resize_Image(Stream streamImage, int maxWidth, int maxHeight)

    {

        Bitmap originalImage = new Bitmap(streamImage);

        int newWidth = originalImage.Width;

        int newHeight = originalImage.Height;

        double aspectRatio = Convert.ToDouble(originalImage.Width) / Convert.ToDouble(originalImage.Height);

        if (aspectRatio <= 1 && originalImage.Width > maxWidth)

        {

            newWidth = maxWidth;

            newHeight = Convert.ToInt32(Math.Round(newWidth / aspectRatio));

        }

        else if (aspectRatio > 1 && originalImage.Height > maxHeight)

        {

            newHeight = maxHeight;

            newWidth = Convert.ToInt32(Math.Round(newHeight * aspectRatio));

        }

        return new Bitmap(originalImage, newWidth, newHeight);

    }

VB.NET Code to resize the images

• In the code behind file (.aspx.vb) write the code as:

First Import following namespaces:

Imports System.Drawing

Imports System.Drawing.Drawing2D

Imports System.Drawing.Imaging

Imports System.Drawing.Design

Imports System.IO

• Then write the code as:

Protected Sub btnUpload_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnUpload.Click

        If FileUpload1.HasFile Then

            Dim img As String = String.Empty

            Dim bmpImg As Bitmap = Nothing

            Try

                bmpImg = Resize_Image(FileUpload1.PostedFile.InputStream, 210, 130)

                img = Server.MapPath("images/") + Guid.NewGuid().ToString() + ".png"

                bmpImg.Save(img, ImageFormat.Jpeg)

            Catch ex As Exception

                Response.Write("Error occured: " & ex.Message.ToString())

            Finally

                img = String.Empty

                bmpImg.Dispose()

            End Try

        End If

    End Sub

    Private Function Resize_Image(ByVal streamImage As Stream, ByVal maxWidth As Integer, ByVal maxHeight As Integer) As Bitmap

        Dim originalImage As New Bitmap(streamImage)

        Dim newWidth As Integer = originalImage.Width

        Dim newHeight As Integer = originalImage.Height

        Dim aspectRatio As Double = CDbl(originalImage.Width) / CDbl(originalImage.Height)

        If aspectRatio <= 1 AndAlso originalImage.Width > maxWidth Then

            newWidth = maxWidth

            newHeight = CInt(Math.Round(newWidth / aspectRatio))

        ElseIf aspectRatio > 1 AndAlso originalImage.Height > maxHeight Then

            newHeight = maxHeight

            newWidth = CInt(Math.Round(newHeight * aspectRatio))

        End If

        Return New Bitmap(originalImage, newWidth, newHeight)

    End Function

Note: Uploaded image will be stored in the “images” folder of the root directory in our case. You can change the folder name and location as per your requirement.  Now you can display the resized image on your website.

Now over to you: 
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