add pygments_wcag_check.py

1 files changed, 61 insertions, 0 deletions

diff --git a/pygments_wcag_check.py b/pygments_wcag_check.py
new file mode 100755
index 0000000..2a1e917
--- /dev/null
+++ b/pygments_wcag_check.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+""" Script that checks if Pygments styles meet the WCAG color contrast standards """
+import sys
+import statistics
+
+import pygments.styles
+import wcag_contrast_ratio
+
+def hex2rgb(hexstr):
+    hexstr = hexstr.lstrip('#')
+    r = int(hexstr[:2], 16) / 255
+    g = int(hexstr[2:4], 16) / 255
+    b = int(hexstr[4:], 16) / 255
+    return (r, g, b)
+
+total_wcag_fails = 0
+styles = []
+
+for name in pygments.styles.get_all_styles():
+    style = pygments.styles.get_style_by_name(name)
+    bgcolor = hex2rgb(style.background_color)
+    contrasts = [
+        (
+            wcag_contrast_ratio.rgb(
+                bgcolor,
+                hex2rgb(style['color'] or '#000000')
+                # we default to black because browsers also do
+            ),
+            ttype
+        ) for ttype, style in style.list_styles()
+    ]
+    if len(contrasts) == 0:
+        continue
+
+    styles.append(
+        (statistics.mean([x[0] for x in contrasts]), min([x[0] for x in contrasts]), name)
+    )
+
+    bad_contrasts = [c for c in contrasts if not wcag_contrast_ratio.passes_AA(c[0])]
+
+    print(f'=== {name} ===')
+    if len(bad_contrasts) > 0:
+        for contrast, ttype in sorted(bad_contrasts):
+            print(f'{contrast:.2f} {ttype}')
+    else:
+        print('meets AA standard')
+    print()
+
+    total_wcag_fails += len(bad_contrasts)
+
+if total_wcag_fails:
+    print(f'found {total_wcag_fails} contrasts that fail to meet the WCAG AA standard')
+    print('''According to WCAG:
+     AA contrast is >= 4.5
+    AAA contrast is >= 7.0
+    ''')
+    print('=== Styles ranked by contrast ===')
+    print(' avg   min  name')
+    for contrast, minimum, name in sorted(styles):
+        print(f'{contrast:4.1f}  {minimum:4.1f}  {name}')
+    sys.exit(1)