[Mono-dev] Convert.ToBase64String yields different result than on windows...

[Quandary]

Hmm, strange...

It turns out that when you have

----------------------------------------------------
<%@ Page Language="C#" %>

    <script runat="server">

public void WriteImage()
{
    // Write image to output stream
    // Response.End()
}   

</script><% WriteImage(); %>

----------------------------------------------------

You may not have a whitespace/tab/newline between </script> and <%
WriteImage %> ...
Apart from that, although base64 encoding returns a different string on
Windows and Linux,
the string created on Windows can be decoded and returns a valid image
on Linux too, although the base64 string is different for the same image...
Very strange.
I have not yet tested whether the string created on Linux will work on
Windows, but I suppose so.

> On 06/04/2011 08:19 PM, Quandary wrote:
>> Hi,
>>
>> Question on the below code (with mono 2.10.2):
>> I'm converting an image to base64 string, and use this string to embed
>> it on a webpage, there I write the image back in the ResponseStream.
>>
>> For that I use the below code, using
>> Convert.ToBase64String on the image byte array.
>>
>> It seems it results in a different base64 string on Linux than on Windows.
>> With PHP, it doesn't.
>>
>> To reproduce:
>> Encode an image (i used gif format) on Windows to base64.
>> Then put the resulting base64 string into a string on an asp.net
>> website, and base64 decode that string there, writing the image to the
>> output stream.
>> It works fine on Windows.
>> It works fine on Linux.
>> But if you base64 encode the image on windows, and put the result string
>> from windows into the decoding website on Linux, then you will get an
>> invalid image..
>>  
>> If you copy the base64 string generated on Windows to Linux into a PHP
>> site, and base64 decode it there, it results in a perfectly fine image.
>>
>> I think this is a bug...
>> And if it is, this should be put into a unit test.
>> Because once base64 values are in a database, you can't just correct the
>> encoding/decoding algorithms, because in the database there will still
>> be values encoded by the old faulty algorithm (I do this in a reporting
>> service solution, to get the logo image for each customer into the
>> header)...
>>
>>
>> Here the code:
>> Note that you need to put a constant as value into variable str to cause
>> the error.
>>
>> ------------------ Code running on Linux
>> string strBase64Content = "base 64 converted image string here";
>> byte[] bt64 = System.Convert.FromBase64String(strBase64Content);
>>     //string strMIME = GetImageMime(ref bt64);
>>    
>>    
>>     Response.ContentType = "image/gif"; //strMIME;
>>     Response.OutputStream.Write(bt64, 0, strBase64Content.Length);
>>     Response.End();
>> --------------------------------------------
>>
>>
>>
>>
>>         void _Default_Load(object sender, EventArgs e)
>>         {
>>             string strPath = Server.MapPath("~/file.gif");
>>             System.Drawing.Image imgThisImage =
>> System.Drawing.Image.FromFile(strPath);
>>             
>>             string str = ImageToBase64(imgThisImage,
>> System.Drawing.Imaging.ImageFormat.Gif);
>>
>>
>>             Base64ToImage(str);
>>             Response.Write(str);
>>             // load event
>>         }
>>         
>>         
>>         public string ImageToBase64(System.Drawing.Image image,
>>               System.Drawing.Imaging.ImageFormat format)
>>         {
>>               using (System.IO.MemoryStream ms = new
>> System.IO.MemoryStream())
>>               {
>>                 // Convert Image to byte[]
>>                 image.Save(ms, format);
>>                 byte[] imageBytes = ms.ToArray();
>>
>>                 // Convert byte[] to Base64 String
>>                 string base64String = Convert.ToBase64String(imageBytes);
>>                 return base64String;
>>               }
>>         }
>>         
>>         
>>         public System.Drawing.Image Base64ToImage(string base64String)
>>         {
>>               // Convert Base64 String to byte[]
>>               byte[] imageBytes = Convert.FromBase64String(base64String);
>>               System.IO.MemoryStream ms = new
>> System.IO.MemoryStream(imageBytes, 0, imageBytes.Length);
>>             
>>             // Convert byte[] to Image
>>               ms.Write(imageBytes, 0, imageBytes.Length);
>>               System.Drawing.Image image =
>> System.Drawing.Image.FromStream(ms, true);
>>               return image;
>>         }
>>