How to Resize image without losing quality in Asp.net

Introduction: In this article I will explain how we can Resizes the image, Validate fileupload control in Asp.net.

Description:

In the previous article I have explained How to Validate theFileupload in Asp.net.

Add a webform to project. Keep the below given script between Head Tag:

<script type="text/javascript">

         function validatefileupload() {

             var arrayExt = ['png', 'PNG', 'jpg', 'JPG', 'JPEG', 'gif', 'GIF', 'jpeg'];

             var FilesVale = document.getElementById("uploadimg");

             var Ext = FilesVale.value.substring(FilesVale.value.lastIndexOf('.') + 1).toLowerCase();

             if (arrayExt.indexOf(Ext) <= -1) {

                 alert("Upload Only png,jpg,gif files");

                 return false;

             }

             else {

                 alert("File Upload Successfully..")

             }

         }

    </script>

Drag and drop the Fileupload control from Toolbox. Here I create a Folder Upload_Images and its sub folder Thumb and Small to save Resized Images.

<table border="1px solid">

       <tr><b>Upload,Validate and Resize the Images in Asp.net</b></tr>

       <tr><td>Upload Images</td><td> <asp:FileUpload ID="uploadimg" runat="server" /></td></tr>

    <tr><td>&nbsp;</td><td><asp:Button ID="Button1" runat="server"

            Text="Upload" onclick="Button1_Click"  OnClientClick="return validatefileupload();"/></td></tr>

    </table>

Now on button click write the below mention code (.aspx.cs):

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

using System.Drawing.Design;

using System.IO;

protected void Button1_Click(object sender, EventArgs e)

    {

        if (uploadimg.HasFile)

        {

            string imgThumb = string.Empty;

            string imgSmall = string.Empty;           

            Bitmap bmpThumb = null;

            Bitmap bmpSmall = null;

            try

            {

                bmpThumb = Resize_Images(uploadimg.PostedFile.InputStream, 100, 67);

                bmpSmall = Resize_Images(uploadimg.PostedFile.InputStream, 411, 270);

                imgThumb = Server.MapPath("Upload_Images/Thumb/") + Guid.NewGuid().ToString() + ".png";

                imgSmall = Server.MapPath("Upload_Images/Small/") + Guid.NewGuid().ToString() + ".png";                

                bmpThumb.Save(imgThumb, ImageFormat.Jpeg);

                bmpSmall.Save(imgSmall, ImageFormat.Jpeg);               

            }

            catch (Exception ex)

            {

               

            }

            finally

            {

                imgThumb = string.Empty;

                imgSmall = string.Empty;

                bmpThumb.Dispose();

                bmpSmall.Dispose();

            }

    }

    }

    private Bitmap Resize_Images(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);

    }

In VB (.aspx.vb)

Imports System.Drawing

Imports System.Drawing.Drawing2D

Imports System.Drawing.Imaging

Imports System.Drawing.Design

Imports System.IO

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

        If uploadimg.HasFile Then

            Dim imgThumb As String = String.Empty

            Dim imgSmall As String = String.Empty

            Dim bmpThumb As Bitmap = Nothing

            Dim bmpSmall As Bitmap = Nothing

            Try

                bmpThumb = Resize_Images(uploadimg.PostedFile.InputStream, 100, 67)

                bmpSmall = Resize_Images(uploadimg.PostedFile.InputStream, 411, 270)

                imgThumb = Server.MapPath("Upload_Images/Thumb/") + Guid.NewGuid().ToString() + ".png"

                imgSmall = Server.MapPath("Upload_Images/Small/") + Guid.NewGuid().ToString() + ".png"

                bmpThumb.Save(imgThumb, ImageFormat.Jpeg)

                bmpSmall.Save(imgSmall, ImageFormat.Jpeg)

            Catch ex As Exception

            Finally

                imgThumb = String.Empty

                imgSmall = String.Empty

                bmpThumb.Dispose()

                bmpSmall.Dispose()

            End Try

        End If

    End Sub

    Private Function Resize_Images(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 = Convert.ToDouble(originalImage.Width) / Convert.ToDouble(originalImage.Height)

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

            newWidth = Maxwidth

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

        ElseIf aspectRatio > 1 AndAlso originalImage.Height > Maxheight Then

            newHeight = Maxheight

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

        End If

        Return New Bitmap(originalImage, newWidth, newHeight)

    End Function

Build and check the result.

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