add an operator to send a GAMAimage to websocket using base64

gama.core/src/gama/core/kernel/root/PlatformAgent.java

@@ -534,6 +534,10 @@
 	 * @date 3 nov. 2023
 	 */
 	public void sendMessage(final IScope scope, final Object message) {
+		sendMessage(scope,GamaServerMessage.Type.SimulationOutput);
+	}
+
+	public void sendMessage(final IScope scope, final Object message, final gama.core.runtime.server.GamaServerMessage.Type type) {
 		try {
 			var socket = scope.getServerConfiguration().socket();
 			// try to get the socket in platformAgent if the request is too soon before agent.schedule()
@@ -543,7 +547,7 @@
 						+ message);
 				return;
 			}
-			socket.send(jsonEncoder.valueOf(new GamaServerMessage(GamaServerMessage.Type.SimulationOutput, message,
+			socket.send(jsonEncoder.valueOf(new GamaServerMessage(type, message,
 					scope.getServerConfiguration().expId())).toString());
 		} catch (Exception ex) {
 			ex.printStackTrace();

gama.core/src/gama/core/runtime/server/GamaServerMessage.java

@@ -60,6 +60,11 @@ public enum Type {
 		 */
 		SimulationOutput,
 
+		/**
+		 * Used to send a image of a display of a running simulation
+		 */
+		SimulationImage,
+
 		/**
 		 * Used to describe the content printed using the debug statement in a running simulation
 		 */

gama.extension.image/src/gama/extension/image/ImageOperators.java

@@ -23,6 +23,13 @@
 import java.awt.image.ColorModel;
 import java.awt.image.RescaleOp;
 import java.awt.image.WritableRaster;
+import java.io.ByteArrayOutputStream;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.util.Base64;
+
+import javax.imageio.ImageIO;
 
 import gama.annotations.precompiler.GamlAnnotations.doc;
 import gama.annotations.precompiler.GamlAnnotations.example;
@@ -33,11 +40,14 @@
 import gama.core.common.interfaces.IDisplaySurface;
 import gama.core.common.interfaces.IKeyword;
 import gama.core.kernel.experiment.ITopLevelAgent;
+import gama.core.kernel.root.PlatformAgent;
 import gama.core.metamodel.agent.IAgent;
 import gama.core.metamodel.shape.GamaPoint;
 import gama.core.outputs.IOutput;
 import gama.core.outputs.LayeredDisplayOutput;
+import gama.core.runtime.GAMA;
 import gama.core.runtime.IScope;
+import gama.core.runtime.server.GamaServerMessage;
 import gama.core.util.GamaColor;
 import gama.core.util.matrix.GamaIntMatrix;
 import gama.core.util.matrix.IMatrix;
@@ -157,6 +167,35 @@ public static GamaImage snapshot(final IScope scope, final IAgent exp, final Str
 		IDisplaySurface surface = ldo.getSurface();
 		return SnapshotMaker.getInstance().captureImage(surface, customDimensions);
 	}
+
+	public static String imgToBase64String(final GamaImage img, final String formatName)
+	{
+	  final ByteArrayOutputStream os = new ByteArrayOutputStream();
+
+	  try
+	  {
+	    ImageIO.write(img, formatName, os);
+	    return Base64.getEncoder().encodeToString(os.toByteArray());
+	  }
+	  catch (final IOException ioe)
+	  {
+	    throw new UncheckedIOException(ioe);
+	  }
+	}
+
+	@operator (
+			value = "send_image_to_websocket",
+			can_be_const = false)
+	@doc ("Takes a snapshot of the display whose name is passed in parameter and returns the image. "
+			+ "The search for the display begins in the agent passed in parameter and, if not found, its experiment. A custom size (a point representing width x height) can be given "
+			+ "Returns nil if no display can be found or the snapshot cannot be taken.")
+	@no_test
+	public static GamaImage sendImageWebsocket(final IScope scope, final GamaImage image) {
+		PlatformAgent pa = GAMA.getPlatformAgent();
+
+		pa.sendMessage(scope, imgToBase64String(image, "png"), GamaServerMessage.Type.SimulationImage);
+		return image;
+	}
 
 	/**
 	 * Grayscale.