Image resizing with asp.net

Introduction

Sometime when we are uploading images and if we resize with applying variable size then images are not displayed in good quality. So, this article show how to resize images without scratch the image.

Background

In this article we have to use some drawing methods.

Using the code

' Create new stream.
' Dim stream As New FileStream(fileName, FileMode.Open, FileAccess.Read)

' Create new image.
Dim image As System.Drawing.Image = System.Drawing.Image.FromStream(Stream)

' Calculate proportional max width and height.
Dim oldWidth As Integer = image.Width
Dim oldHeight As Integer = image.Height
If (CDec(oldWidth) / CDec(oldHeight)) > (CDec(newWidth) / CDec(newHeight)) Then
    Dim ratio As Decimal = CDec(newWidth) / oldWidth
    newHeight = CInt((oldHeight * ratio))
Else
    Dim ratio As Decimal = CDec(newHeight) / oldHeight
    newWidth = CInt((oldWidth * ratio))
End If

' Create a new bitmap with the same resolution as the original image.
Dim bitmap As New Bitmap(newWidth, newHeight, PixelFormat.Format24bppRgb)
bitmap.SetResolution(image.HorizontalResolution, image.VerticalResolution)

' Create a new graphic.
Dim graphics__1 As Graphics = Graphics.FromImage(bitmap)
graphics__1.Clear(Color.White)
graphics__1.InterpolationMode = InterpolationMode.HighQualityBicubic

' Create a scaled image based on the original.
graphics__1.DrawImage(image, New Rectangle(0, 0, newWidth, newHeight),
                      New Rectangle(0, 0, oldWidth, oldHeight), GraphicsUnit.Pixel)
                      graphics__1.Dispose()

 ' Save the scaled image.
 bitmap.Save(Server.MapPath("Images/") & strDestinationFileName, image.RawFormat)