add fast_colorthief backend

pywal/backends/fast_colorthief.py

@@ -0,0 +1,50 @@
+"""
+Generate a colorscheme using fast_colorthief.
+"""
+import logging
+import sys
+
+try:
+    import fast_colorthief
+
+except ImportError:
+    logging.error("fast_colorthief wasn't found on your system.")
+    logging.error("Try another backend. (wal --backend)")
+    sys.exit(1)
+
+from .. import util
+
+
+def gen_colors(img):
+    """ Ask backend to generate 16 colors. """
+    raw_colors = fast_colorthief.get_palette(img, 16)
+
+    return [util.rgb_to_hex(color) for color in raw_colors]
+
+
+def adjust(cols, light):
+    """Create palette."""
+    cols.sort(key=util.rgb_to_yiq)
+    raw_colors = [*cols, *cols]
+
+    if light:
+        raw_colors[0] = util.lighten_color(cols[0], 0.90)
+        raw_colors[7] = util.darken_color(cols[0], 0.75)
+
+    else:
+        for color in raw_colors:
+            color = util.lighten_color(color, 0.40)
+
+        raw_colors[0] = util.darken_color(cols[0], 0.80)
+        raw_colors[7] = util.lighten_color(cols[0], 0.60)
+
+    raw_colors[8] = util.lighten_color(cols[0], 0.20)
+    raw_colors[15] = raw_colors[7]
+
+    return raw_colors
+
+
+def get(img, light=False):
+    """Get colorscheme."""
+    cols = gen_colors(img)
+    return adjust(cols, light)