The trick I have used is to encode the image in Base64, and then send the
image as a String in the return.
public String getDither(int steps, double spiralDistance, double magnitude)
{
... make the image ( a spiral dither pattern) and save to disk
return Base64.encodeFromFile("myFile.png");
}
On Wed, Feb 10, 2010 at 12:50 PM, Ralf B <[email protected]> wrote:
> Hello everybody,
>
> I am new to GWT and want to have a service that transfers an Image
> object (com.google.gwt.user.client.ui.Image) back to the client.
> (Using GWT 2.0.0 with Eclipse Galileo and Eclipse GWT plugin).
>
> On the client, I have the following service method:
>
> import com.google.gwt.user.client.ui.Image;
> Image getImage();
>
> and the following service async method:
>
> import com.google.gwt.user.client.ui.Image;
> void getImage(AsyncCallback<Image> callback);
>
>
> On the server, I have the following service implementation:
>
>
> import com.google.gwt.user.client.ui.Image;
> @Override
> public Image getEventTimeline() {
>
> // 1) code to generate image from data
>
> // 2) create new image and return to client
> Image image = new Image("test.png");
> return image;
> }
>
> When I compile the code, I get the following error:
>
> ....[ERROR] com.google.gwt.user.client.ui.Image is not assignable to
> 'com.google.gwt.user.client.rpc.IsSerializable' or
> 'java.io.Serializable' nor does it have a custom field serializer
> (reached via com.google.gwt.user.client.ui.Image)
> [ERROR] com.google.gwt.user.client.ui.Image has no
> available instantiable subtypes. (reached via
> com.google.gwt.user.client.ui.Image)
> [ERROR] subtype
> com.google.gwt.user.client.ui.Image is not assignable to
> 'com.google.gwt.user.client.rpc.IsSerializable' or
> 'java.io.Serializable' nor does it have a custom field serializer
> (reached via com.google.gwt.user.client.ui.Image)....
>
> This suggests that an Image cannot be serialized. I have two questions
> about this:
>
> 1) Isn't every Google object serializable by default. Otherwise, what
> is the point of having a separate image class in GWT?
>
> 2) What is the proper way of doing this? I want to create the image
> server-sided every time a user clicks a button and return it back to
> the user where it is supposed to be displayed in a panel.
>
> Any suggestions?
>
> Thanks a lot,
>
> Ralf
>
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