asp.net image aspect ratio help

Question

Hey all, i am in need of some help with keeping an image aspect ratio in check. This is the aspx code that i have to resize and upload an image the user selects.

 <%@ Page Trace="False" Language="vb" aspcompat="false" debug="true" validateRequest="false"%> 
 <%@ Import Namespace=System.Drawing %>
 <%@ Import Namespace=System.Drawing.Imaging %>
 <%@ Import Namespace=System %>
 <%@ Import Namespace=System.Web %>
 <SCRIPT LANGUAGE="VBScript" runat="server">
 const Lx = 500 ' max width for thumbnails
 const Ly = 60  ' max height for thumbnails
 const upload_dir = "/uptest/"  ' directory to upload file
 const upload_original = "sample"   ' filename to save original as (suffix added by script)
 const upload_thumb = "thumb"   ' filename to save thumbnail as (suffix added by script)
 const upload_max_size = 512    ' max size of the upload (KB) note: this doesn't override any server upload limits
 dim fileExt    ' used to store the file extension (saves finding it mulitple times)
 dim newWidth, newHeight as integer ' new width/height for the thumbnail
 dim l2 ' temp variable used when calculating new size
 dim fileFld as HTTPPostedFile  ' used to grab the file upload from the form
 Dim originalimg As System.Drawing.Image    ' used to hold the original image
 dim msg    ' display results
 dim upload_ok as boolean   ' did the upload work ?
 </script>
 <%
 randomize() ' used to help the cache-busting on the preview images
 upload_ok = false

 if lcase(Request.ServerVariables("REQUEST_METHOD"))="post" then
fileFld = request.files(0)  ' get the first file uploaded from the form (note:- you can use this to itterate through more than one image)
if fileFld.ContentLength > upload_max_size * 1024 then
    msg = "Sorry, the image must be less than " & upload_max_size & "Kb"
else
    try
        originalImg = System.Drawing.Image.FromStream(fileFld.InputStream)
        ' work out the width/height for the thumbnail. Preserve aspect ratio and honour max width/height
        ' Note: if the original is smaller than the thumbnail size it will be scaled up
        if originalImg.Height > Ly then
            newWidth = Ly * (originalImg.Width / originalImg.Height)
            newHeight = Ly
        end if

        Dim thumb As New Bitmap(newWidth, newHeight)

        'Create a graphics object           
        Dim gr_dest As Graphics = Graphics.FromImage(thumb)

        ' just in case it's a transparent GIF force the bg to white 
        dim sb = new SolidBrush(System.Drawing.Color.White)
        gr_dest.FillRectangle(sb, 0, 0, thumb.Width, thumb.Height)

        'Re-draw the image to the specified height and width
        gr_dest.DrawImage(originalImg, 0, 0, thumb.Width, thumb.Height)

        try
            fileExt = System.IO.Path.GetExtension(fileFld.FileName).ToLower()
            originalImg.save(Server.MapPath(upload_dir & upload_original & fileExt), originalImg.rawformat)
            thumb.save(Server.MapPath(upload_dir & upload_thumb & fileExt), originalImg.rawformat)
            msg = "Uploaded " & fileFld.FileName & " to " & Server.MapPath(upload_dir & upload_original & fileExt)
            upload_ok = true
        catch
            msg = "Sorry, there was a problem saving the image."
        end try
        ' Housekeeping for the generated thumbnail
        if not thumb is nothing then
            thumb.Dispose()
            thumb = nothing
        end if
    catch
        msg = "Sorry, that was not an image we could process."
    end try
end if

' House Keeping !
if not originalImg is nothing then
    originalImg.Dispose()
    originalImg = nothing
end if

 end if
 %>

What i am looking for is a way to just have it go by the height of what i set it:

 const Ly = 60  ' max height for thumbnails

And have the code for the width just be whatever. So if i had an image... say 600 x 120 (w h) and i used photoshop to change just the height, it would keep it in ratio and have it 300 x 60 (w x h). Thats what i am looking to do with this code here. However, i can not think of a way to do this (or to just leave a wildcard for the width setting.

Any help would be great :o)

David

Answer 1

Couldn't you just replace that whole if/else/endif block with something along these lines?

if oldImage.Height > Ly then
    newWidth = Ly * (NewImage.Width / NewImage.Height)
    newHeight = Ly
end if