perf(screenshot): use sampling for is-white (#570)

* test(screenshot): add is-white assertion

* perf: use sampling

* test: update snapshot

packages/goto/test/unit/evasions/index.js

@@ -152,7 +152,7 @@ test('media codecs are present', async t => {
       }
     })
 
-  t.deepEqual(await videoCodecs(), { ogg: 'probably', h264: 'probably', webm: 'probably' })
+  t.deepEqual(await videoCodecs(), { ogg: '', h264: 'probably', webm: 'probably' })
 
   t.deepEqual(await audioCodecs(), {
     ogg: 'probably',

packages/screenshot/src/is-white-screenshot.js

@@ -8,8 +8,12 @@ module.exports = async buffer => {
   const height = image.getHeight()
   const width = image.getWidth()
 
-  for (let i = 0; i < height; i++) {
-    for (let j = 0; j < width; j++) {
+  const samplePercentage = 0.25 // Sample 25% of the image
+  const sampleSize = Math.floor(width * height * samplePercentage) // Calculate sample size based on percentage
+  const stepSize = Math.max(1, Math.floor((width * height) / sampleSize)) // Calculate step size based on sample size
+
+  for (let i = 0; i < height; i += stepSize) {
+    for (let j = 0; j < width; j += stepSize) {
       if (firstPixel !== image.getPixelColor(j, i)) return false
     }
   }

packages/screenshot/test/is-white-screenshot.js

@@ -0,0 +1,16 @@
+'use strict'
+
+const test = require('ava')
+const { readFile } = require('fs/promises')
+
+const isWhite = require('../src/is-white-screenshot')
+
+test('true', async t => {
+  t.true(await isWhite(await readFile('./test/fixtures/white-5k.jpg')))
+  t.true(await isWhite(await readFile('./test/fixtures/white-5k.png')))
+})
+
+test('false', async t => {
+  t.false(await isWhite(await readFile('./test/fixtures/no-white-5k.jpg')))
+  t.false(await isWhite(await readFile('./test/fixtures/no-white-5k.png')))
+})