Added feature to saveCanvas() to support framebuffer

src/image/image.js

@@ -99,7 +99,7 @@ p5.prototype.createImage = function(width, height) {
  *  file immediately or prompt the user with a dialogue window.
  *
  *  @method saveCanvas
- *  @param  {p5.Element|HTMLCanvasElement} selectedCanvas   reference to a
+ *  @param  {p5.Framebuffer|p5.Element|HTMLCanvasElement} selectedCanvas   reference to a
  *                                                          specific HTML5 canvas element.
  *  @param  {String} [filename]  file name. Defaults to 'untitled'.
  *  @param  {String} [extension] file extension, either 'jpg' or 'png'. Defaults to 'png'.
@@ -175,14 +175,26 @@ p5.prototype.saveCanvas = function() {
 
   // copy arguments to array
   const args = [].slice.call(arguments);
-  let htmlCanvas, filename, extension;
+  let htmlCanvas, filename, extension, temporaryGraphics;
 
   if (arguments[0] instanceof HTMLCanvasElement) {
     htmlCanvas = arguments[0];
     args.shift();
   } else if (arguments[0] instanceof p5.Element) {
     htmlCanvas = arguments[0].elt;
     args.shift();
+  } else if (arguments[0] instanceof p5.Framebuffer) {
+    const framebuffer = arguments[0];
+    temporaryGraphics = this.createGraphics(framebuffer.width,
+      framebuffer.height);
+    temporaryGraphics.pixelDensity(pixelDensity());
+    framebuffer.loadPixels();
+    temporaryGraphics.loadPixels();
+    temporaryGraphics.pixels.set(framebuffer.pixels);
+    temporaryGraphics.updatePixels();
+
+    htmlCanvas = temporaryGraphics.elt;
+    args.shift();
   } else {
     htmlCanvas = this._curElement && this._curElement.elt;
   }
@@ -213,6 +225,7 @@ p5.prototype.saveCanvas = function() {
 
   htmlCanvas.toBlob(blob => {
     p5.prototype.downloadFile(blob, filename, extension);
+    if(temporaryGraphics) temporaryGraphics.remove();
   }, mimeType);
 };