Merge pull request scratchfoundation#415 from mzgoddard/drop-silhouette-alpha-buffer

Replace Silhouette._data with Silhouette._colorData

Author: mzgoddard

src/Silhouette.js

@@ -19,12 +19,12 @@ let __SilhouetteUpdateCanvas;
  * @param {number} y - y
  * @return {number} Alpha value for x/y position
  */
-const getPoint = ({_width: width, _height: height, _data: data}, x, y) => {
+const getPoint = ({_width: width, _height: height, _colorData: data}, x, y) => {
     // 0 if outside bouds, otherwise read from data.
     if (x >= width || y >= height || x < 0 || y < 0) {
         return 0;
     }
-    return data[(y * width) + x];
+    return data[(((y * width) + x) * 4) + 3];
 };
 
 /**
@@ -76,7 +76,6 @@ class Silhouette {
          * The data representing a skin's silhouette shape.
          * @type {Uint8ClampedArray}
          */
-        this._data = null;
         this._colorData = null;
 
         this.colorAtNearest = this.colorAtLinear = (_, dst) => dst.fill(0);
@@ -100,16 +99,11 @@ class Silhouette {
         ctx.drawImage(bitmapData, 0, 0, width, height);
         const imageData = ctx.getImageData(0, 0, width, height);
 
-        this._data = new Uint8ClampedArray(imageData.data.length / 4);
         this._colorData = imageData.data;
         // delete our custom overriden "uninitalized" color functions
         // let the prototype work for itself
         delete this.colorAtNearest;
         delete this.colorAtLinear;
-
-        for (let i = 0; i < imageData.data.length; i += 4) {
-            this._data[i / 4] = imageData.data[i + 3];
-        }
     }
 
     /**
@@ -166,7 +160,7 @@ class Silhouette {
      * @return {boolean} If the nearest pixel has an alpha value.
      */
     isTouchingNearest (vec) {
-        if (!this._data) return;
+        if (!this._colorData) return;
         return getPoint(
             this,
             Math.floor(vec[0] * (this._width - 1)),
@@ -181,7 +175,7 @@ class Silhouette {
      * @return {boolean} Any of the pixels have some alpha.
      */
     isTouchingLinear (vec) {
-        if (!this._data) return;
+        if (!this._colorData) return;
         const x = Math.floor(vec[0] * (this._width - 1));
         const y = Math.floor(vec[1] * (this._height - 1));
         return getPoint(this, x, y) > 0 ||