Disegno Tecnico: BMP convertiti in PNG nel browser, errore upload nel riquadro. Refs #107

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/frontend/flask_app/tests/js/test_image_to_png.js

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+/**
+ * image_to_png.js, run with plain node (#107): solo la parte pura (niente canvas qui).
+ * Run from src/frontend/flask_app: node tests/js/test_image_to_png.js
+ */
+'use strict';
+const path = require('path');
+const { tmfNeedsPng, tmfImageToPng } = require(
+  path.join(__dirname, '..', '..', 'static', 'js', 'image_to_png.js'),
+);
+
+let failures = 0;
+function check(label, cond) {
+  if (cond) { console.log('ok - ' + label); } else { console.error('FAIL - ' + label); failures++; }
+}
+
+check('bmp va convertito', tmfNeedsPng('image/bmp') === true);
+check('tiff va convertito', tmfNeedsPng('image/tiff') === true);
+check('png no', tmfNeedsPng('image/png') === false);
+check('jpeg no', tmfNeedsPng('image/jpeg') === false);
+check('gif no', tmfNeedsPng('image/gif') === false);
+check('webp no', tmfNeedsPng('image/webp') === false);
+check('pdf no', tmfNeedsPng('application/pdf') === false);
+check('tipo vuoto no', tmfNeedsPng('') === false);
+
+(async () => {
+  const fake = { name: 'a.png', type: 'image/png' };
+  check('png ritorna lo stesso oggetto', (await tmfImageToPng(fake)) === fake);
+  const pdf = { name: 'a.pdf', type: 'application/pdf' };
+  check('pdf ritorna lo stesso oggetto', (await tmfImageToPng(pdf)) === pdf);
+  if (failures) { console.error(failures + ' failure(s)'); process.exit(1); }
+  console.log('all ok');
+})();

src/frontend/flask_app/tests/test_image_to_png_js.py

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+"""Runs the plain-node image_to_png.js test (tests/js/test_image_to_png.js).
+
+Covers gitea:Adriano/TieMeasureFlow#107.
+"""
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+FLASK_APP_DIR = Path(__file__).resolve().parent.parent
+JS_TEST = Path(__file__).resolve().parent / "js" / "test_image_to_png.js"
+
+
+def test_image_to_png_js_pure_behaviour():
+    node = shutil.which("node")
+    if not node:
+        pytest.skip("node non installato: test JS di image_to_png.js saltato")
+
+    result = subprocess.run(
+        [node, str(JS_TEST)],
+        cwd=str(FLASK_APP_DIR),
+        capture_output=True,
+        text=True,
+        timeout=30,
+    )
+
+    assert result.returncode == 0, (
+        f"tests/js/test_image_to_png.js fallito (exit {result.returncode})\n"
+        f"stdout:\n{result.stdout}\nstderr:\n{result.stderr}"
+    )