From b2c320503b0fd04ddc6e2e991630a0e17797a47a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Corentin=20S=C3=A9chet?= <csechet@entrouvert.com>
Date: Fri, 8 Apr 2022 14:32:05 +0200
Subject: [PATCH] screenshot: save only files where there is a diff

---
 frontools/screenshot.py | 39 ++++++++++++++++++++++++++++-----------
 pyproject.toml          |  2 ++
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/frontools/screenshot.py b/frontools/screenshot.py
index 292fbed..d29436a 100644
--- a/frontools/screenshot.py
+++ b/frontools/screenshot.py
@@ -1,7 +1,9 @@
 """Pages screenshots"""
 from pathlib import Path
+from tempfile import NamedTemporaryFile
 from typing import Optional
 
+from PIL import Image, ImageChops
 from playwright.async_api import BrowserContext
 
 from frontools import Config
@@ -60,21 +62,36 @@ async def screenshot_diff(
 async def _diff_url(
     left: BrowserContext, right: BrowserContext, url: str, output_path: Path
 ) -> None:
-    await _screenshot_url(left, url, output_path, "left")
-    await _screenshot_url(right, url, output_path, "right")
+    left_bytes = await _screenshot_url(left, url)
+    right_bytes = await _screenshot_url(right, url)
 
+    with NamedTemporaryFile(mode='wb') as left_file:
+        left_file.write(left_bytes)
+        left_image = Image.open(left_file.name)
+
+    with NamedTemporaryFile(mode='wb') as right_file:
+        right_file.write(right_bytes)
+        right_image = Image.open(right_file.name)
+
+    diff = ImageChops.difference(left_image, right_image)
+
+    if not diff.getbbox(): # images are the same
+        return
 
-async def _screenshot_url(
-    browser: BrowserContext, url: str, output_path: Path, suffix: str
-) -> None:
-    page = await browser.new_page()
-    await page.goto(url)
-    await page.wait_for_load_state('networkidle')
     url_slug = get_url_slug(url)
     if not output_path.is_dir():
         output_path.mkdir()
 
-    screenshot_bytes = await page.screenshot(full_page=True)
+    with open(output_path / f"{url_slug}_left", "wb") as screenshot_file:
+        screenshot_file.write(left_bytes)
 
-    with open(output_path / f"{url_slug}_{suffix}", "wb") as screenshot_file:
-        screenshot_file.write(screenshot_bytes)
+    with open(output_path / f"{url_slug}_right", "wb") as screenshot_file:
+        screenshot_file.write(right_bytes)
+
+
+async def _screenshot_url(browser: BrowserContext, url: str) -> bytes:
+    page = await browser.new_page()
+    await page.goto(url)
+    await page.wait_for_load_state("networkidle")
+
+    return await page.screenshot(full_page=True)
diff --git a/pyproject.toml b/pyproject.toml
index 5f938d7..6628fdf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,6 +38,7 @@ click = "^8.0.4"
 aiohttp = "^3.8.1"
 PyYAML = "^6.0"
 tinycss2 = "^1.1.1"
+Pillow = "^9.1.0"
 
 [tool.poetry.dev-dependencies]
 isort = "^5.10.1"
@@ -45,6 +46,7 @@ black = "^22.1.0"
 mypy = "^0.942"
 pylint = "^2.13.2"
 types-click = "^7.1.8"
+types-Pillow = "^9.0.11"
 
 [tool.poetry-dynamic-versioning]
 enable = true