Question

The white background after re-sizing the image using VB.net as shown below. I tried to change some values but failed.

Dim FileToResize As String = Server.MapPath("~/images/" & filename & FileUpload1.FileName)
Using originalBitmap As Bitmap = Bitmap.FromFile(FileToResize, True), newbmp As Bitmap = New Bitmap(200, 200)
    Dim WidthVsHeightRatio = CDec(originalBitmap.Width) / CDec(originalBitmap.Height)

    Using newg As Graphics = Graphics.FromImage(newbmp)
        newg.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
        newg.Clear(Color.White)

        If WidthVsHeightRatio = 1D Then
            newg.DrawImage(originalBitmap, 0, 0, 200, 200)
            newg.Save()


        ElseIf WidthVsHeightRatio < 1D Then 'Image is taller than wider

            newg.DrawImage(originalBitmap, New RectangleF(New PointF((100 - (200 * WidthVsHeightRatio) / 2), 0), New SizeF(200 * WidthVsHeightRatio, 200.0F)))
            newg.Save()

        Else 'Image is wider than taller

            Dim inverse As Double = Math.Pow(WidthVsHeightRatio, -1)
            newg.DrawImage(originalBitmap, New RectangleF(New PointF(0, 100 - ((200 * inverse) / 2)), New SizeF(200.0F, 200 * inverse)))
            newg.Save()
        End If
    End Using

    newbmp.Save(Server.MapPath("~/images/" & "_th_" & filename & FileUpload1.FileName), System.Drawing.Imaging.ImageFormat.Jpeg)
    NewsItem.ImageLink = filename & FileUpload1.FileName
    NewsItem.smallimage = "_th_" & filename & FileUpload1.FileName
End Using

Answer 1

I did a bit of research recently for generating Image Thumbnails on the fly for an eCommerce site. I started off doing this myself generating a bitmap and then resizing etc. After problems with image size on disc and quality I looked in to http://imageresizing.net/ and I haven’t looked back since. It can generate images from byte(), streams and physicals files all very quickly with one line of code:

ImageBuilder.Current.Build(New MemoryStream(bImage), sImageLocation + sFullFileName, New      ResizeSettings("maxwidth=214&maxheight=238"))

I would definitely recommend this component rather than trying to reinvent the wheel…