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tests/visual-hash.test.mjs

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+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { createRequire } from 'node:module';
+const { visualFingerprint, hammingDistance } = createRequire(import.meta.url)('../packages/core/visual-hash.cjs');
+function image(width = 64, height = 64, layout = 0, brightness = 0) {
+  const rgba = new Uint8Array(width * height * 4);
+  for (let y = 0; y < height; y++) for (let x = 0; x < width; x++) {
+    const nx = x / width, ny = y / height;
+    let value = 220;
+    if (!layout) {
+      if (ny < 0.2) value = 45;
+      if (nx > 0.2 && nx < 0.8 && ny > 0.35 && ny < 0.8) value = 140;
+      if (nx > 0.3 && nx < 0.7 && ny > 0.5 && ny < 0.6) value = 65;
+    } else {
+      if (nx < 0.25) value = 65;
+      if (nx > 0.4 && nx < 0.9 && ny > 0.2 && ny < 0.45) value = 120;
+      if (nx > 0.6 && ny > 0.7) value = 45;
+    }
+    const index = (y * width + x) * 4;
+    rgba[index] = rgba[index + 1] = rgba[index + 2] = value + brightness; rgba[index + 3] = 255;
+  }
+  return { rgba, width, height };
+}
+test('DCT fingerprints are deterministic, brightness stable and resize tolerant', () => {
+  const original = visualFingerprint(image());
+  assert.equal(original.algorithm, 'phash-dct32-v1'); assert.match(original.hash, /^[0-9a-f]{16}$/); assert.equal(original.usable, true);
+  assert.deepEqual(visualFingerprint(image()), original);
+  assert.equal(hammingDistance(original.hash, visualFingerprint(image(64, 64, 0, 12)).hash), 0);
+  assert.ok(hammingDistance(original.hash, visualFingerprint(image(128, 128)).hash) <= 6);
+});
+test('blank low contrast and transparent images are unusable', () => {
+  for (const value of [0, 127, 255]) {
+    const rgba = new Uint8Array(64 * 64 * 4);
+    for (let index = 0; index < rgba.length; index += 4) { rgba[index] = rgba[index + 1] = rgba[index + 2] = value; rgba[index + 3] = 255; }
+    const result = visualFingerprint({ rgba, width: 64, height: 64 }); assert.equal(result.usable, false); assert.equal(result.quality.contrast, 0);
+  }
+  const transparent = image(); for (let index = 3; index < transparent.rgba.length; index += 4) transparent.rgba[index] = 0;
+  assert.equal(visualFingerprint(transparent).usable, false);
+});
+test('different layouts exceed the conservative similarity threshold', () => {
+  const distance = hammingDistance(visualFingerprint(image()).hash, visualFingerprint(image(64, 64, 1)).hash);
+  assert.ok(distance > 10, `distance ${distance}`);
+});
+test('crop normalizes selected region and clamps safe partial intersections', () => {
+  const input = image();
+  assert.deepEqual(visualFingerprint({ ...input, region: { x: -10, y: -10, width: 74, height: 74 } }), visualFingerprint(input));
+  const cropped = visualFingerprint({ ...input, region: { x: 15, y: 15, width: 40, height: 40 } });
+  assert.notEqual(cropped.hash, visualFingerprint(input).hash);
+});
+test('malformed dimensions buffers crop and hash formats are rejected', () => {
+  const input = image();
+  for (const change of [{ width: -1 }, { width: 1.5 }, { width: 9000 }, { height: 9000 }, { rgba: [1, 2, 3] }, { rgba: new Uint8Array(4) }, { region: { x: 100, y: 100, width: 3, height: 3 } }, { region: { x: 0, y: 0, width: 0, height: 4 } }, { region: { x: Infinity, y: 0, width: 4, height: 4 } }]) assert.throws(() => visualFingerprint({ ...input, ...change }));
+  assert.throws(() => visualFingerprint({ rgba: new Uint8Array(4), width: 8192, height: 8192 }));
+  assert.throws(() => hammingDistance('A'.repeat(16), '0'.repeat(16))); assert.throws(() => hammingDistance('0', '0'.repeat(16)));
+  assert.equal(hammingDistance('0'.repeat(16), 'f'.repeat(16)), 64);
+});