Feature: Add to-base64 and from-base64

Author: LaCuneta

README.md

@@ -43,6 +43,8 @@ will be imported as well.
 [`bitmap:copy-to-pcolors`](#bitmapcopy-to-pcolors)
 [`bitmap:difference-rgb`](#bitmapdifference-rgb)
 [`bitmap:export`](#bitmapexport)
+[`bitmap:from-base64`](#bitmapfrom-base64)
+[`bitmap:to-base64`](#bitmapto-base64)
 [`bitmap:from-view`](#bitmapfrom-view)
 [`bitmap:to-grayscale`](#bitmapto-grayscale)
 [`bitmap:height`](#bitmapheight)
@@ -127,6 +129,24 @@ bitmap:export image filename
 Writes *image* to *filename*.
 
 
+### `bitmap:from-base64`
+
+```NetLogo
+bitmap:from-base64 base64-string
+```
+
+Turns a base64 encoded string into a bitmap image for use by the extension.  The [Fetch](https://github.com/NetLogo/Fetch-Extension) and [Export-The](https://github.com/NetLogo/ExportThe-Extension) extensions would be common sources of these encoded strings.
+
+
+### `bitmap:to-base64`
+
+```NetLogo
+bitmap:to-base64 base64-string
+```
+
+Turns a bitmap image into a base64 encoded string with a PNG format.
+
+
 ### `bitmap:from-view`
 
 ```NetLogo

documentation.conf

@@ -94,6 +94,20 @@ the same width and height as each other, or errors will ensue.
     arguments: [ { name: image, type: bitmap }, { name: filename, type: string } ],
     description: "Writes *image* to *filename*.",
   },
+  {
+    name: from-base64
+    type: reporter
+    arguments: [ { name: base64-string, type: string } ]
+    returns: bitmap
+    description: "Turns a base64 encoded string into a bitmap image for use by the extension.  The [Fetch](https://github.com/NetLogo/Fetch-Extension) and [Export-The](https://github.com/NetLogo/ExportThe-Extension) extensions would be common sources of these encoded strings."
+  },
+  {
+    name: to-base64
+    type: reporter
+    arguments: [ { name: base64-string, type: string } ]
+    returns: string
+    description: "Turns a bitmap image into a base64 encoded string with a PNG format."
+  },
   {
     name: from-view,
     type: reporter,

src/BitmapExtension.java

@@ -16,13 +16,22 @@
 import org.nlogo.nvm.Workspace;
 
 import java.awt.image.BufferedImage;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.Base64;
+import javax.imageio.ImageIO;
 
 public class BitmapExtension extends DefaultClassManager {
 
   public void load(PrimitiveManager primitiveManager) {
     primitiveManager.addPrimitive("import", new LoadImage());
     // saves to disk as PNG format
     primitiveManager.addPrimitive("export", new SaveImage());
+
+    primitiveManager.addPrimitive("from-base64", new FromBase64());
+    primitiveManager.addPrimitive("to-base64", new ToBase64());
+
     // returns a LogoBitmap image from NetLogo's primary view, as if by export-view
     primitiveManager.addPrimitive("from-view", new GrabView());
 
@@ -73,7 +82,7 @@ public Object report(Argument args[], Context context)
       try {
         String path = fm.attachPrefix(args[0].getString());
         return new LogoBitmap(
-            javax.imageio.ImageIO.read(fm.getFile(path).getInputStream()));
+            ImageIO.read(fm.getFile(path).getInputStream()));
       } catch (java.io.IOException e) {
         throw new ExtensionException(e.getMessage());
       }
@@ -99,14 +108,66 @@ public void perform(Argument args[], Context context)
         String filename = context.attachCurrentDirectory(args[1].getString());
         java.io.FileOutputStream stream =
             new java.io.FileOutputStream(filename);
-        javax.imageio.ImageIO.write(image, "png", stream);
+        ImageIO.write(image, "png", stream);
         stream.close();
       } catch (java.io.IOException e) {
         throw new ExtensionException(e.getMessage());
       }
     }
   }
 
+  public static class FromBase64 implements Reporter {
+
+    public Syntax getSyntax() {
+      return SyntaxJ.reporterSyntax(new int[] { Syntax.StringType() }, Syntax.WildcardType());
+    }
+
+    public String getAgentClassString() {
+      return "OTPL";
+    }
+
+    public Object report(Argument args[], Context context)
+        throws ExtensionException, LogoException {
+      String base64 = args[0].getString();
+      byte[] bytes   = Base64.getDecoder().decode(base64);
+      try {
+        BufferedImage image = ImageIO.read(new ByteArrayInputStream(bytes));
+        return new LogoBitmap(image);
+      }
+      catch (final IOException ex) {
+        throw new ExtensionException(ex);
+      }
+    }
+
+  }
+
+  public static class ToBase64 implements Reporter {
+
+    public Syntax getSyntax() {
+      return SyntaxJ.reporterSyntax(new int[] { Syntax.WildcardType() }, Syntax.StringType());
+    }
+
+    public String getAgentClassString() {
+      return "OTPL";
+    }
+
+    public Object report(Argument args[], Context context)
+        throws ExtensionException, LogoException {
+      BufferedImage image = getBitmapFromArgument(args[0]);
+
+      final ByteArrayOutputStream baos = new ByteArrayOutputStream();
+
+      try {
+        ImageIO.write(image, "png", baos);
+        return Base64.getEncoder().encodeToString(baos.toByteArray());
+      }
+      catch (final IOException ex) {
+        throw new ExtensionException(ex);
+      }
+    }
+
+  }
+
   public static class GrabView implements Reporter {
 
     public Syntax getSyntax() {