✨ empty space node

package.json

@@ -1,6 +1,6 @@
 {
   "name": "graphfx",
-  "version": "0.0.13",
+  "version": "0.0.15",
   "description": "Graph image processing pipeline",
   "main": "src/index.js",
   "scripts": {

src/nodes/Canvas2d/EmptySpace.js

@@ -0,0 +1,69 @@
+import Canvas2d from './Canvas2d';
+import {createCanvas, mediaSize, paintToCanvas} from '../canvas';
+
+export default class EmptySpace extends Canvas2d {
+
+    constructor() {
+        super('EmptySpace', {
+        }, {
+        w: {
+          type: 'Number',
+        },
+        h: {
+            type: 'Number',
+        },
+        top: {
+          type: 'Number',
+        },
+        right: {
+          type: 'Number',
+        },
+        bottom: {
+          type: 'Number',
+        },
+        left: {
+          type: 'Number',
+        }
+      });
+      this._update();
+    }
+
+    async render({image}, canvas, ctx) {
+      if (!image) {
+        return;
+      }
+      let left = Infinity;
+      let right = -Infinity;
+      let top = Infinity;
+      let bottom = -Infinity;
+
+      const {width, height} = mediaSize(image);
+      canvas.width = width;
+      canvas.height = height;
+      ctx.drawImage(image, 0, 0);
+      const imageData = ctx.getImageData(0, 0, width, height)
+      for (let offset=0; offset<imageData.data.length; offset+=4) {
+        const x = (offset/4) % width;
+        const y = Math.floor((offset/4) / width)
+        const [r,g,b,a] = imageData.data.slice(offset, offset+4);
+        if (a < 1) {
+          top = Math.min(top, y);
+          right = Math.max(right, x);
+          bottom = Math.max(bottom, y);
+          left = Math.min(left, x);
+        }
+        imageData.data[offset] = a;
+        imageData.data[offset + 1] = a;
+        imageData.data[offset + 2] = a;
+        imageData.data[offset + 3] = a;
+      }
+      ctx.putImageData(imageData, 0, 0);
+      this.out.top.value = top;
+      this.out.right.value = right;
+      this.out.bottom.value = bottom;
+      this.out.left.value = left;
+      this.out.w.value = right - left;
+      this.out.h.value = bottom - top;
+      return canvas;
+  }
+}

src/nodes/index.js

@@ -4,6 +4,7 @@ export {default as Resize} from './Canvas2d/Resize';
 export {default as Compose} from './Canvas2d/Compose';
 export {default as Fill} from './Canvas2d/Fill';
 export {default as Flip} from './Canvas2d/Flip';
+export {default as EmptySpace} from './Canvas2d/EmptySpace';
 // export {default as ImageIdentity} from './Canvas2d/ImageIdentity';
 export {default as Text} from './Canvas2d/Text';
  // WebGL