[Editor] (WIP) Add a new tool in order to add an handwritten signatur…

…e to a pdf (bug 1942343)

This patch is adding some code in order to extract a drawing as curves from an image.
The algorithm is basically the following:
 - reduce the dimensions
 - make it gray
 - apply a bilateral filter in order to add some blurryness while keeping the edges
 - compute the histogram
 - guess what's the background color which should contain a large majority of the pixels
 - make a binary image
 - extract the contours in using the Suzuki algorithm
 - apply the Douglas-Peucker algorithm in order to reduce the number of points

The algorithm is improvable but it should work pretty well if there's a clear difference between
the background and the drawing.
In a v2 we could use a ML model in order to improve the extraction.

There's few changes related to the UI in order to make the tool usable, but they're very basic
for the moment.

extensions/chromium/preferences_schema.json

@@ -71,6 +71,10 @@
       "type": "string",
       "default": ""
     },
+    "enableSignatureEditor": {
+      "type": "boolean",
+      "default": false
+    },
     "enableUpdatedAddImage": {
       "type": "boolean",
       "default": false

src/display/editor/annotation_editor_layer.js

@@ -31,6 +31,7 @@ import { FreeTextEditor } from "./freetext.js";
 import { HighlightEditor } from "./highlight.js";
 import { InkEditor } from "./ink.js";
 import { setLayerDimensions } from "../display_utils.js";
+import { SignatureEditor } from "./signature.js";
 import { StampEditor } from "./stamp.js";
 
 /**
@@ -89,10 +90,13 @@ class AnnotationEditorLayer {
   static _initialized = false;
 
   static #editorTypes = new Map(
-    [FreeTextEditor, InkEditor, StampEditor, HighlightEditor].map(type => [
-      type._editorType,
-      type,
-    ])
+    [
+      FreeTextEditor,
+      InkEditor,
+      StampEditor,
+      HighlightEditor,
+      SignatureEditor,
+    ].map(type => [type._editorType, type])
   );
 
   /**
@@ -758,7 +762,11 @@ class AnnotationEditorLayer {
       return;
     }
 
-    if (this.#uiManager.getMode() === AnnotationEditorType.STAMP) {
+    const currentMode = this.#uiManager.getMode();
+    if (
+      currentMode === AnnotationEditorType.STAMP ||
+      currentMode === AnnotationEditorType.SIGNATURE
+    ) {
       this.#uiManager.unselectAll();
       return;
     }

src/display/editor/draw.js

@@ -91,6 +91,10 @@ class DrawingEditor extends AnnotationEditor {
     super(params);
     this.#mustBeCommitted = params.mustBeCommitted || false;
 
+    this._addOutlines(params);
+  }
+
+  _addOutlines(params) {
     if (params.drawOutlines) {
       this.#createDrawOutlines(params);
       this.#addToDrawLayer();

src/display/editor/drawers/contour.js

@@ -0,0 +1,28 @@
+/* Copyright 2024 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { InkDrawOutline } from "./inkdraw.js";
+
+class ContourDrawOutline extends InkDrawOutline {
+  toSVGPath() {
+    let path = super.toSVGPath();
+    if (!path.endsWith("Z")) {
+      path += "Z";
+    }
+    return path;
+  }
+}
+
+export { ContourDrawOutline };