Added convenience script show_cmaps.py

- visualize multiple color maps at once, and all built-in ones by
  default

share/scripts/show_cmaps.py

@@ -0,0 +1,28 @@
+'''Script to visually inspect color maps.'''
+import click
+import numpy as np
+from PIL import Image
+
+from zennit.image import CMAPS, palette
+
+
+def semsstr(string):
+    if isinstance(string, list):
+        return string
+    return [obj for obj in string.split(';') if obj]
+
+
+@click.command()
+@click.argument('output')
+@click.option('--cmap', 'colormap_src', type=semsstr, default=list(CMAPS))
+@click.option('--level', type=float, default=1.0)
+def main(output, colormap_src, level):
+    print('\n'.join(colormap_src))
+    palettes = np.stack([palette(obj, level) for obj in colormap_src])
+    arr = np.repeat(palettes, 32, 0)
+    img = Image.fromarray(arr)
+    img.save(output)
+
+
+if __name__ == '__main__':
+    main()