asp.net image aspect ratio help
- by StealthRT
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.Width/Lx) > (originalImg.Width/Ly) Then
L2 = originalImg.Width
newWidth = Lx
newHeight = originalImg.Height * (Lx / L2)
if newHeight > Ly then
newWidth = newWidth * (Ly / newHeight)
newHeight = Ly
end if
Else
L2 = originalImg.Height
newHeight = Ly
newWidth = originalImg.Width * (Ly / L2)
if newWidth > Lx then
newHeight = newHeight * (Lx / newWidth)
newWidth = Lx
end if
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
