docs: check images size is not larger than 600K

.travis.yml

@@ -62,6 +62,7 @@ jobs:
         - markdownlint -V
       script:
         - markdownlint docs
+        - ./check_files_size.py
         - gitbook install
         - gitbook build
       deploy:

check_files_size.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+
+def human_size(num, suffix='B'):
+    for unit in ['', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi']:
+        if abs(num) < 1024.0:
+            return "%3.1f %s%s" % (num, unit, suffix)
+        num /= 1024.0
+    return "%.1f %s%s" % (num, 'Yi', suffix)
+
+SIZE_LIMIT = 600 * 1024
+EXCLUDE = 'rviz.png', 'ssid.png', 'sitl_docker_demo.png', 'qgc-params.png', 'butterfly.png', \
+    'Clever main.png', 'fpv_3.png', '1_4.png', 'fpv_4.png', 'detal1.png', 'lockradio.png', \
+    'qground.png', 'allElements.png', 'download-log.png', 'explosion.png', 'rqt.png', \
+    'cl3_mountBEC.JPG', 'cl3_mountRpiCamera.JPG'
+
+code = 0
+
+for root, dirs, files in os.walk('docs/'):
+    for f in files:
+        if f not in EXCLUDE:
+            path = os.path.join(root, f)
+            size = os.path.getsize(path)
+            if size > SIZE_LIMIT:
+                print('\x1b[1;31mFile too large ({}): {}\x1b[0m'.format(human_size(size), path), \
+                    file=sys.stderr)
+                code = 1
+
+sys.exit(code)