Returning a Bitmap Object from a WebMethod

[rlcavebmg]

I am new to Web Services and .NET development, and I have a question.

I am writing a service that will create a bitmap image and return it to the
client. First, I wrote a method that looked like this:

public System.Drawing.Bitmap CreateImage() {...}

When I tried to create the web reference in my client program, I got an
error message stating that the System.Drawing.Bitmap object could not be
serialized because it does not have a public default constructor. Then I
changed the method to something like this:

public bool CreateImage(ref System.Drawing.Bitmap bitmap) {...}

Unfortunately, this resulted in the same error message.

The help for the Bitmap class indicates that it has been declared with the
[serializable] attribute, which leads me to believe that what I am doing
should work. Alas, it does not.

Does anyone know what I need to do to make this work, or have a sample
program that does something similar?

Thanks,

Bob

[Drew Marsh]

rlcavebmg wrote:

I am new to Web Services and .NET development, and I have a question.

I am writing a service that will create a bitmap image and return it
to the client. First, I wrote a method that looked like this:

... snipped for brevity ...

Does anyone know what I need to do to make this work, or have a sample
program that does something similar?

Yeah, you can't just return a Bitmap for a bunch of reasons. What you'll
need to do is get the bytes of the bitmap and return them using Base64 encoding.
It might look a little something like this:

<codeSnippet language="C#">
[WebMethod]
[return:XmlElement("imageData", DataType="base64Binary")]
public byte[] CreateImage()
{
using(Bitmap image = new Bitmap(100, 100))
using(Graphics imageGraphics = Graphics.FromImage(image))
{
imageGraphics.FillRectangle(Brushes.Red, 0, 0, image.Width, image.Height);
imageGraphics.DrawRectangle(Pens.Blue, 0, 0, image.Width, image.Height);

using(MemoryStream stream = new MemoryStream())
{
image.Save(stream, ImageFormat.Png);

stream.Flush();

return stream.ToArray();
}
}
}
</codeSnippet>

As you can see I've decorated the result of the method with an XmlElementAttribute
with the DataType base64Binary which instructs the XmlSerializer to serialize
the byte array into an element named "imageData" whose contents is base64
encoded. This is not the most efficient way to acheive this since you need
to encode/decode the bytes, but is probably the most cross platform compatible.
If you're using WSE on both ends you might want to consider using DIME, which
will allow you to basically send just the raw bytes, but that's something
I'm not all that experienced with personally.

HTH,
Drew

[rlcavebmg]

"Drew Marsh" wrote:

...snipped for brevity...

Drew,

Thanks. That was very helpful.

On the client side, it looks like I ought to be able to do something like
the following snippet to get the data into a Bitmap object:

byte[] byteArray = CreateImage();
MemoryStream stream = new MemoryStream(byteArray);
Bitmap bitmap = new Bitmap(stream);

Is this correct?

Cheers,

Bob

[Drew Marsh]

rlcavebmg wrote:

On the client side, it looks like I ought to be able to do something
like the following snippet to get the data into a Bitmap object:

Duh, yeah, I shoulda just included my test client side code for you. Here,
this was on a test winforms app as part of a button click. It just gets the
image and draws it on the form:

<codeSnippet language="C#">
Service1 service = new Service1();

byte[] imageBytes = service.CreateImage();

using(MemoryStream stream = new MemoryStream(imageBytes, false))
using(Image image = Image.FromStream(stream))
{
this.CreateGraphics().DrawImage(image, 0, 0);
}
</codeSnippet>

HTH,
Dre

[Dilip Krishnan]

Hello Drew,
Ideally you should try using Dime attachments.
http://msdn.microsoft.com/msdnmag/is...E/default.aspx
HTH
Regards,
Dilip Krishnan
MCAD, MCSD.net
dkrishnan at geniant dot com
http://www.geniant.com

rlcavebmg wrote:

On the client side, it looks like I ought to be able to do something
like the following snippet to get the data into a Bitmap object:

Duh, yeah, I shoulda just included my test client side code for you.
Here, this was on a test winforms app as part of a button click. It
just gets the image and draws it on the form:

<codeSnippet language="C#">
Service1 service = new Service1();
byte[] imageBytes = service.CreateImage();

using(MemoryStream stream = new MemoryStream(imageBytes, false))
using(Image image = Image.FromStream(stream))
{
this.CreateGraphics().DrawImage(image, 0, 0);
}
</codeSnippet>

HTH,
Drew

[Bahadir Cambel]

Could you please write an example of a web application doing the same job..
Because I am dealing with the same issue , tranferring byte[] from the
WebService, but I couldnt find any method to transform this data into a
WebControls.Image object.
Thanks a lot ,
Bahadir Cambel

"Drew Marsh" wrote:

rlcavebmg wrote:

On the client side, it looks like I ought to be able to do something
like the following snippet to get the data into a Bitmap object:

Duh, yeah, I shoulda just included my test client side code for you. Here,
this was on a test winforms app as part of a button click. It just gets the
image and draws it on the form:

<codeSnippet language="C#">
Service1 service = new Service1();

byte[] imageBytes = service.CreateImage();

using(MemoryStream stream = new MemoryStream(imageBytes, false))
using(Image image = Image.FromStream(stream))
{
this.CreateGraphics().DrawImage(image, 0, 0);
}
</codeSnippet>

HTH,
Drew

[Cor Ligthert]

Hi,

I saw this question by accident, does this sample I once made fit the
problem?
As database is a very easy dataset file used on the serverside.

\\\needs a picturebox and 4 buttons on a windowform
Private ds As New DataSet
Private abyt() As Byte
Private fo As New OpenFileDialog
Private sf As New SaveFileDialog
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
'Reading a picture from disk and put it in a bytearray
If fo.ShowDialog = DialogResult.OK Then
Dim fs As New IO.FileStream(fo.FileName, _
IO.FileMode.Open)
Dim br As New IO.BinaryReader(fs)
abyt = br.ReadBytes(CInt(fs.Length))
br.Close()
'just to show the sample without a fileread error
Dim ms As New IO.MemoryStream(abyt)
Me.PictureBox1.Image = Image.FromStream(ms)
End If
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal _
e As System.EventArgs) Handles Button2.Click
'writing a picture from a bytearray to disk
If sf.ShowDialog = DialogResult.OK Then
Dim fs As New IO.FileStream(sf.FileName, _
IO.FileMode.CreateNew)
Dim bw As New IO.BinaryWriter(fs)
bw.Write(abyt)
bw.Close()
End If
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal _
e As System.EventArgs) Handles Button3.Click
'writing a bytearray to a webservice dataset
Dim ws As New localhost.DataBaseUpdate
ws.SetDataset(abyt)
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button4.Click
'reading a picture from a webservice dataset
Dim ws As New localhost.DataBaseUpdate
abyt = ws.GetByte
Dim ms As New IO.MemoryStream(abyt)
Me.PictureBox1.Image = Image.FromStream(ms)
End Sub
End Class
////
\\\\Webservice
<WebMethod()> _
Public Function GetByte() As Byte()
Dim ds As New DataSet
ds.ReadXml("C:\wsblob.xml")
Return CType(ds.Tables(0).Rows(0)(0), Byte())
End Function
<WebMethod()> _
Public Sub SetDataset(ByVal abyte As Byte())
Dim ds As New DataSet
ds.Tables.Add(New DataTable("Photo"))
ds.Tables(0).Columns.Add(New DataColumn("Sample"))
ds.Tables(0).Columns(0).DataType = GetType(System.Byte())
ds.Tables(0).Rows.Add(ds.Tables(0).NewRow)
ds.Tables(0).Rows(0)(0) = abyte
ds.WriteXml("C:\wsblob.xml", XmlWriteMode.WriteSchema)
End Sub
////

I hope this helps a little bit?

Cor
"rlcavebmg" <rl*******@discussions.microsoft.com>

I am new to Web Services and .NET development, and I have a question.

I am writing a service that will create a bitmap image and return it to
the
client. First, I wrote a method that looked like this:

public System.Drawing.Bitmap CreateImage() {...}

When I tried to create the web reference in my client program, I got an
error message stating that the System.Drawing.Bitmap object could not be
serialized because it does not have a public default constructor. Then I
changed the method to something like this:

public bool CreateImage(ref System.Drawing.Bitmap bitmap) {...}

Unfortunately, this resulted in the same error message.

The help for the Bitmap class indicates that it has been declared with the
[serializable] attribute, which leads me to believe that what I am doing
should work. Alas, it does not.

Does anyone know what I need to do to make this work, or have a sample
program that does something similar?

Thanks,

Bob