Convert.ToBase64 question - C# Discussion Boards

28-Aug-05 16:53

Hi,
I'm trying to get a base64 string from an image to place inside a WordProcessingML xml document. I need to save the image to a stream after it's generated through asp.net, that is, I'm not able to use the file system. For some reason, I seem to get a different string loading something from the file system and using file streams and binary readers, as opposed to when I use Image.Save and a memory stream. I've pasted some sample code below, it's not my actual code that I'm working with but simulates the situation. The two methods generate different strings from the same image file. If I reverse the process, and take the two generated strings and load them into an image, both work fine. No doubt there is some obvious encoding issue or something that I'm sadly unaware of so if anyone had any ideas that'd be great.

FileStream fs = File.OpenRead(@"C:\temp\chart.png");
BinaryReader br = new BinaryReader(fs);
string pngString = Convert.ToBase64String(br.ReadBytes((int)fs.Length));

MemoryStream memStream = new MemoryStream();
Image image = Image.FromFile(@"C:\temp\chart.png");
image.Save(memStream,System.Drawing.Imaging.ImageFormat.Png);
string memString = Convert.ToBase64String(memStream.GetBuffer());

Thanks,
Matt

Andy Brummer28-Aug-05 17:06

28-Aug-05 17:06

if you do an image.Save to a binaryWriter do you get the same files? There is a form of image.Save which takes encoding parameters. You probably have to set these to match the original file.

[Message Deleted]

matt cole28-Aug-05 18:25

28-Aug-05 18:25

[Message Deleted]

matt cole28-Aug-05 18:26

28-Aug-05 18:26

Hi Andy,
I didn't actually even save the image programatically, as I mentioned the snippet I've pasted in isn't the actual code I'm working with it's just a test that I wrote up to see what the problem was in my actual code. The image on disk has just been saved straight from a browser so I could use it in the test. Don't know if this makes any difference to you?

Thanks,
Matt

Andy Brummer28-Aug-05 19:13

28-Aug-05 19:13

I don't think the image object makes any promises about Load() and Save() generating the exact same bits. I just suggested a test to verify that.

Unless you have to use the image object to manipulate the image in some way I would just deal with it as a stream. That's how I've always dealt with them in WordprocessingML documents.

I can imagine the sinking feeling one would have after ordering my book,
only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon

[Message Deleted]

matt cole28-Aug-05 19:18

28-Aug-05 19:18

[Message Deleted]

matt cole28-Aug-05 19:19

28-Aug-05 19:19

Yeah my actual code does deal with it as a stream but it generates the same string as the Image.Save(memoryStream) method. Basically I'm using a third party charting component which has a save method which is able to save to a stream, I assume it uses the same method as the Image.Save does as it generates the same base64 string. I was hoping if i could get to the bottom of the reason I am getting two different strings I could take that solution to my actual code.

I can see now that the string is exactly the same, except the file IO method has more bytes on the end that are missing from the other method.

Aplication.run

xilefxilef28-Aug-05 16:22

xilefxilef

28-Aug-05 16:22

Hi I have two forms, main form and login form, I need both forms to load at the start of my application (login form in front of main). The user shouild not be able to switch focus to the main form intil a successful login is accomplished. I'm loading both forms from a main method of another class. I played around with Application.run and ShowDialog methods without achieving wanted results. Any ideas are appriciated.

Thank you

Andy Brummer28-Aug-05 16:59

28-Aug-05 16:59

Using application.run you can load your login form before the main form.
What you are describing sounds like you want to use ShowDialog in the activated or paint event to set an authentication token in the main form. That way you will have both forms on the screen at the same time.

Luis Alonso Ramos28-Aug-05 17:04

Luis Alonso Ramos

28-Aug-05 17:04

What I would do is run the main form normally, and then handle the Activated event for the form, and if it's the first time, display the dialog.

bool firstTime = true;
 
protected override void OnActivated(EventArgs e)
{
    if(firstTime)
    {
        firstTime = false;
        LoginForm form = new LoginForm();
        form.ShowDialog(this);
    }
}

That should work, displaying the main form and the login form on top of it.

But, my real solution would be to implement a main form with everything disabled if no user is logged in. This way a user can log in, then log out, and then another user log in without terminating your app, and only the corresponding menu items would be enabled.

And then, in the Activated event for the first time, simulate that the Log In menu item was selected. This way, if the user can't log in (invalid user or password), the application does not have to end.

-- LuisR

Luis Alonso Ramos
Intelectix - Chihuahua, Mexico

Not much here: My CP Blog!

The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005

xilefxilef28-Aug-05 18:45

xilefxilef

28-Aug-05 18:45

If I understood correctly, both suggestions involve controling the displaying of the login form from within the main form. Is there a way to accomplish the same thing (displaying both forms) from a 'static void Main() ' method from a third class- the class that I'll use to start the application.

Thank you in advance

Andy Brummer28-Aug-05 19:26

28-Aug-05 19:26

The reason we are suggesting this is because it is the way that .net forms are implemented. The typical windows approach for this type of UI is to use a modal dialog which prevents the parent form from accepting input while the modal dialog is active.

If you don't care about disabling the main form you can just call Show() on the login form and ShowDialog on the main form, then both forms will be active. However, you need to setup some way for both forms to share state information and keep thier UIs synchronized.

I can imagine the sinking feeling one would have after ordering my book,
only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon

Luis Alonso Ramos28-Aug-05 20:07

Luis Alonso Ramos

28-Aug-05 20:07

The thing is that Application.Run blocks until your form is closed, so you can't do anything from your Main while your form is displayed. You either have to display the login form and act on it before displaying your main form, or display your login form from within your main form.

-- LuisR

Luis Alonso Ramos
Intelectix - Chihuahua, Mexico

Not much here: My CP Blog!

The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005