cleanup interpolation artifacts that may hinder inference

src/main.js

@@ -17,7 +17,7 @@ const backendloaded = (async () => {
   try {
     // dead code elimination should occur here
     // eslint-disable-next-line camelcase
-    if (execution_mode === 'userscript') {
+    if (execution_mode === 'userscript' || execution_mode === 'test') {
       weightsData = (await import('./model.weights.bin')).default
       const tfwasmthreadedsimd = (await import('./tfjs-backend-wasm-threaded-simd.wasm')).default
       const tfwasmsimd = (await import('./tfjs-backend-wasm-simd.wasm')).default
@@ -148,7 +148,7 @@ function imageFromCanvas (img, bg, off) {
   canvas.height = w * scale + pw * 2
   canvas.width = th
 
-  const ctx = canvas.getContext('2d')
+  const ctx = canvas.getContext('2d', { willReadFrequently: true })
 
   ctx.fillStyle = 'rgb(238,238,238)'
   ctx.fillRect(0, 0, canvas.width, canvas.height)
@@ -161,6 +161,7 @@ function imageFromCanvas (img, bg, off) {
 
   const draw = function (off, adj) {
     if (adj) {
+      // stretching might cause interpolation that throws off the model, might need to clean up
       if (bg) {
         const border = 4
         ctx.drawImage(
@@ -254,6 +255,14 @@ async function predict (img, bg, off) {
   }
   const image = imageFromCanvas(img, bg, off)
 
+  for (let i = 0; i < image.data.length; i += 4) {
+    if (image.data[i + 0] ||
+        image.data[i + 1] ||
+        image.data[i + 2]) {
+      image.data[i + 0] = image.data[i + 1] = image.data[i + 2] = 238
+    }
+  }
+
   const tensor = tf.browser
     .fromPixels(image, 1)
     .mul(-1 / 238)
@@ -379,7 +388,8 @@ async function imageFromUri (uri) {
   if (uri.startsWith('url("')) {
     uri = uri.substr(5, uri.length - 7)
   }
-  if (!uri.startsWith('data:')) {
+  // eslint-disable-next-line camelcase
+  if (execution_mode !== 'test' && !uri.startsWith('data:')) {
     return null
   }