How to Resize image without losing quality in Asp.net | ASPMANTRA | Asp.Net,MVC,AngularJs,Jquery,Javascript,Sql Server AND WCF snippets and tutorial

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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