Handle subscription of messages in the webapp.
Messages larger than a threshold are split and reassembled due to the
size limit in webrtc. Threshold may have to be adjusted somewhere between
64KiB and 256KiB.
This also includes a basic handler for a ping message and a more
advanced image handler.
Change-Id: If66acfb1bb84e9d3ff686994a94b1480cb70b2aa
diff --git a/y2020/www/image_handler.ts b/y2020/www/image_handler.ts
new file mode 100644
index 0000000..abaf831
--- /dev/null
+++ b/y2020/www/image_handler.ts
@@ -0,0 +1,61 @@
+import {frc971} from 'y2020/vision/vision_generated';
+
+export class ImageHandler {
+ private canvas = document.createElement('canvas');
+
+ constructor() {
+ document.body.appendChild(this.canvas);
+ }
+
+ handleImage(data: Uint8Array) {
+ const fbBuffer = new flatbuffers.ByteBuffer(data);
+ const image = frc971.vision.CameraImage.getRootAsCameraImage(fbBuffer);
+
+ const width = image.cols();
+ const height = image.rows();
+ if (width === 0 || height === 0) {
+ return;
+ }
+ const imageBuffer = new Uint8ClampedArray(width * height * 4); // RGBA
+
+ // Read four bytes (YUYV) from the data and transform into two pixels of
+ // RGBA for canvas
+ for (const j = 0; j < height; j++) {
+ for (const i = 0; i < width; i += 2) {
+ const y1 = image.data((j * width + i) * 2);
+ const u = image.data((j * width + i) * 2 + 1);
+ const y2 = image.data((j * width + i + 1) * 2);
+ const v = image.data((j * width + i + 1) * 2 + 1);
+
+ // Based on https://en.wikipedia.org/wiki/YUV#Converting_between_Y%E2%80%B2UV_and_RGB
+ const c1 = y1 - 16;
+ const c2 = y2 - 16;
+ const d = u - 128;
+ const e = v - 128;
+
+ imageBuffer[(j * width + i) * 4 + 0] = (298 * c1 + 409 * e + 128) >> 8;
+ imageBuffer[(j * width + i) * 4 + 1] =
+ (298 * c1 - 100 * d - 208 * e + 128) >> 8;
+ imageBuffer[(j * width + i) * 4 + 2] = (298 * c1 + 516 * d + 128) >> 8;
+ imageBuffer[(j * width + i) * 4 + 3] = 255;
+ imageBuffer[(j * width + i) * 4 + 4] = (298 * c2 + 409 * e + 128) >> 8;
+ imageBuffer[(j * width + i) * 4 + 5] =
+ (298 * c2 - 100 * d - 208 * e + 128) >> 8;
+ imageBuffer[(j * width + i) * 4 + 6] = (298 * c2 + 516 * d + 128) >> 8;
+ imageBuffer[(j * width + i) * 4 + 7] = 255;
+ }
+ }
+
+ const ctx = this.canvas.getContext('2d');
+
+ this.canvas.width = width;
+ this.canvas.height = height;
+ const idata = ctx.createImageData(width, height);
+ idata.data.set(imageBuffer);
+ ctx.putImageData(idata, 0, 0);
+ }
+
+ getId() {
+ return frc971.vision.CameraImage.getFullyQualifiedName();
+ }
+}