Tuesday, March 10, 2009

Sharepoint Thumbnails and AssetUploader.aspx

We recently had a consultant build a web part for us that displayed thumbnails from images in a document library. In digging around in the code they gave us I discovered that they used a page built into Sharepoint called AssetUploader.aspx (in 12\TEMPLATE\LAYOUTS\AssetUploader.aspx, available off any web at _layouts\AssetUploader.aspx). This page is a rather handy. It's specifically designed to take a URL of an available image, resize it, and spit out a thumbnail. You can use it in any page or web part in Sharepoint by creating an IMG tag like this:
<img src="http://www.blogger.com/_layouts/AssetUploader.aspx?Size=Medium&ImageURL=/mysitecollection/mysite/MyImagesDocumentLibrary/IMG1234.jpg" alt="My Image" />
If you use a size of 'Small', it will make the largest dimension of the image 70 pixels, and if you use anything other than small (Medium, Large, etc.), it will make the largest dimension of the image 140 pixels.

It worked wonderfully in our test environment, but once we brought it into production, it broke. All we saw were little generic white document icons - no thumbnails. Yikes!

I turned, of course, to google, and I found a very helpful post from Bob Moore at PointBridge, where he explained the problem and provided some code as a solution. His code was tremendously helpful, but didn't get me all the way there, so I went to reflector myself to try and disassemble and fix it on my own.

However, interestingly, reflector couldn't disassemble all of it. The main class I was interested in was Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetThumbnailerPage. So I opened it in reflector to find this message when I tried to disassemble the OnLoad event:
// This item is obfuscated and cannot be translated.
I soon found that while Reflector couldn't show me the C# code for that function, I could look at the IL code for it (to do this, click on the language drop down in the toolbar and change it from C# or Visual Basic to IL). I'd never seen this before, but once I found Microsoft's IL reference, I was able to decipher and disassemble it by hand back into C#.

Here is the solution I ended up with that works well with AAM. I created a simple ASPX page containing only this:
<%@ Assembly Name="MyAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=0123456789abcdef"%>
<%@ Page Language="C#" Inherits="MyNamespace.MyAssetThumbnailerPage" %>

And here is the code for the MyAssetThumbnailerPage class, which I included in a DLL that gets deployed via a feature to the GAC:
using System;
using System.Drawing;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
using System.Security.Permissions;
using System.IO;
using System.Globalization;
using System.Drawing.Imaging;
using System.Web;
using System.Collections;

namespace MyNamespace
{
[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
public partial class MyAssetThumbnailerPage : UnsecuredLayoutsPageBase
{

protected override void OnLoad(EventArgs e)
{
int Size;
SPWeb web = null;
SPSite site = null;
try
{
string ImageURL = Request.QueryString["ImageURL"].ToString();
if (Request.QueryString["Size"].ToString() == "Small")
{
Size = 70;
}
else
{
Size = 140;
}

Uri uri = new Uri(SPContext.Current.Web.Url);
string url = uri.Scheme + "://" + uri.Host + ImageURL;
Uri uri2 = new Uri(HttpContext.Current.Request.Url, url);

site = SPContext.Current.Site;
site = new SPSite(SPContext.Current.Web.Url);
SPSecurity.CatchAccessDeniedException = false;
web = site.OpenWeb();
SPFile file;
file = (SPFile)web.GetFileOrFolderObject(uri2.AbsoluteUri);

SPSecurity.CatchAccessDeniedException = true;

if (file == null)
{
Server.Transfer("/_layouts/IMAGES/ICGEN.GIF");
}

if (!IsImageUrl(file.Url))
{
Server.Transfer("/_layouts/IMAGES/" + file.IconUrl);
}

byte[] fileBytes = MyAssetThumbnailer.CreateThumbnail
(file.OpenBinary(),Size);


Response.OutputStream.Write(fileBytes, 0, fileBytes.Length);

base.OnLoad(e);
}
catch (Exception ex)
{
base.OnLoad(e);
}
finally
{
web.Close();
web.Dispose();
site.Close();
site.Dispose();
}
}

private static bool IsImageUrl(string fullUrlToTest)
{
if (!string.IsNullOrEmpty(fullUrlToTest))
{
string str = fullUrlToTest;
int index = fullUrlToTest.IndexOf
("?", StringComparison.Ordinal);

if (-1 == index)
{
index = fullUrlToTest.IndexOf
("#", StringComparison.Ordinal);

}
if (-1 != index)
{
str = fullUrlToTest.Substring(0, index);
}
string str2 = string.Empty;
if (!string.IsNullOrEmpty(str))
{
index = str.LastIndexOf(".", StringComparison.Ordinal);
if (-1 != index)
{
str2 = str.Substring(index);
}
}
//ULS.SendTraceTag(ULSTagID.tag_6osa,
//ULSCat.msoulscat_CMS_Publishing, ULSTraceLevel.Medium,
//"Verifying that the extension [%s] of URL ['%s' - full: " +
//"'%s'] is a recognized image type.",
//new object[] { str2, str, fullUrlToTest });

if (string.IsNullOrEmpty(str2))
{
return false;
}
ArrayList list = new ArrayList(new string[] { ".bmp", ".gif",
".jpeg", ".jpg", ".jpe", ".png" });

return list.Contains(str2.ToLowerInvariant());
}
return false;
}



}

internal class MyAssetThumbnailer
{
private MyAssetThumbnailer()
{

}

public static byte[] CreateThumbnail(byte[] inputBuffer,
int thumbMaxDimension)

{
MemoryStream stream = new MemoryStream(inputBuffer);
Bitmap bitmap = new Bitmap(stream);
Size imageSize = bitmap.Size;
Size size2 =getThumbnailDimensions(imageSize, thumbMaxDimension);
if (size2 == imageSize)
{
object[] objArray = new object[] {
thumbMaxDimension.ToString(CultureInfo.InvariantCulture),
imageSize.Width.ToString(CultureInfo.InvariantCulture),
imageSize.Height.ToString(CultureInfo.InvariantCulture),
inputBuffer.Length.ToString(CultureInfo.InvariantCulture)
};

//ULS.SendTraceTag(ULSTagID.tag_6osl,
//ULSCat.msoulscat_CMS_Publishing, ULSTraceLevel.Medium,
//"No thumbnail made - thumbnail size [%s] is greater " +
//"than image dimensions[%sx%s] bytes: %s", objArray);

return inputBuffer;
}
object[] data = new object[] {
size2.Width.ToString(CultureInfo.InvariantCulture),
size2.Height.ToString(CultureInfo.InvariantCulture),
imageSize.Width.ToString(CultureInfo.InvariantCulture),
imageSize.Height.ToString(CultureInfo.InvariantCulture),
inputBuffer.Length.ToString(CultureInfo.InvariantCulture)
};

//ULS.SendTraceTag(ULSTagID.tag_6osm,
//ULSCat.msoulscat_CMS_Publishing, ULSTraceLevel.Medium,
//"Generating thumbnail with dimensions[%sx%s] for image with " +
//"dimensions[%sx%s] bytes: %s", data);

return imageObjectToBytes(
bitmap.GetThumbnailImage(
size2.Width,
size2.Height,
new System.Drawing.Image.GetThumbnailImageAbort
(MyAssetThumbnailer.thumbnailCallback),
IntPtr.Zero
)
);

}

private static Size getThumbnailDimensions
(Size imageSize, int thumbMaxDimension)

{

if ((imageSize.Height > thumbMaxDimension) ||
(imageSize.Width > thumbMaxDimension))

{
SizeF ef = new SizeF((float)thumbMaxDimension,
(float)thumbMaxDimension);

if (imageSize.Height <= imageSize.Width)
{
ef.Height = (imageSize.Height * thumbMaxDimension) /
imageSize.Width;

}
else
{
ef.Width = (imageSize.Width * thumbMaxDimension) /
imageSize.Height;

}
if (ef.Width <>
{
ef.Width = 1f;
}
if (ef.Height <>
{
ef.Height = 1f;
}
if (ef.Width > thumbMaxDimension)
{
ef.Width = thumbMaxDimension;
}
if (ef.Height > thumbMaxDimension)
{
ef.Height = thumbMaxDimension;
}
return Size.Ceiling(ef);
}
return imageSize;
}

private static byte[] imageObjectToBytes
(System.Drawing.Image imageObject)

{
MemoryStream stream = new MemoryStream();
imageObject.Save(stream, ImageFormat.Jpeg);
return stream.ToArray();
}

private static bool thumbnailCallback()
{
return false;
}
}
}

4 comments:

Biud said...

I tried your solution but it doesn't work.

- I create a strong signed dll with your code.
- I drag this dll in the GAC
- I modify the AssetUploader.aspx page with the reference to my new dll and class.
- I run a issreset

The thumbnails don't appear...

The only thing I replaced in your code was : "MTWAssetThumbnailer.thumbnailCallback" by "MyAssetThumbnailer.thumbnailCallback"

Have I forgot something ?

Excuse my english.
Thanks.

Tim said...

Biud,

Thanks for catching the typo. It has been corrected.

Make sure that you also change the PublicKeyToken to match the assembly you compiled.

Can you post what your HTML/ASPX page looks like, and what your AssetUploader.aspx page looks like?

Are you getting any errors when you try to load your HTML/ASPX/Web Part with the thumbnail in it?

Tim

Biud said...

Tim,

I've this problem on a standard PublishingImages library.

I've changed the PublicKeyToken but I don't see any difference between before and after the modification of the layout...

There is no error on my page, the thumbnails are not displayed (red cross instead) and no error in the event viewer (?!?)

However I'm sure that I've the same problem than you because I succeed to display this thumbnails when I don't use the AAM.

Thanks for your help.

Biud

agorlach said...

Btw, here is a product to display tumbnails for images, Office documents and PDFs in SharePoint 2010 and 2013 document libraries:

http://www.harepoint.com/Products/HarePointThumbnails/Default.aspx

WBR, Alexander