New covers.

[librarian.git] / src / librarian / covers / utils / color.py

diff --git a/src/librarian/covers/utils/color.py b/src/librarian/covers/utils/color.py
new file mode 100644 (file)
index 0000000..afcf38e
--- /dev/null
+++ b/src/librarian/covers/utils/color.py
@@ -0,0 +1,39 @@
+def luminance(rgb):
+    rgb = [
+        c / 255 
+        for c in rgb
+    ]
+    rgb = [
+        c / 12.92 if c < .03928 else ((c + .055) / 1.055) ** 2.4
+        for c in rgb
+    ]
+    return .2126 * rgb[0] + .7152 * rgb[1] + .0722 * rgb[2]
+
+
+def cdist(a, b):
+    d = abs(a-b)
+    if d > 128:
+        d = 256 - d
+    return d
+
+
+def algo_contrast_or_hue(img, colors):
+    rgb = img.convert('RGB').resize((1, 1)).getpixel((0, 0))
+    lumi = luminance(rgb)
+
+    if lumi > .9:
+        return colors[3]
+    elif lumi < .1:
+        return colors[2]
+
+    hue = img.convert('HSV').resize((1, 1)).getpixel((0, 0))[0]
+    return max(
+        colors[:3],
+        key=lambda c: cdist(hue, c['hsv'][0]) ** 2 + (lumi - c['luminance']) ** 2
+    )
+
+
+def is_very_bright(img):
+    rgb = img.convert('RGB').getpixel((0, 0))
+    lumi = luminance(rgb)
+    return lumi > .95