Extracting characters from a PNG

features.py

$ rio insp ~/Desktop/logo.png Rasterio 0.17.1 Interactive Inspector (Python 2.7.9)
Type "src.meta", "src.read_band(1)", or "help(src)" for more information.
>>> red = src.read(1)
>>> red
array([[255, 255, 255, ..., 255, 255, 255],
       [255, 255, 255, ..., 255, 255, 255],
       [255, 255, 255, ..., 255, 255, 255],
       ...,
       [255, 255, 255, ..., 255, 255, 255],
       [255, 255, 255, ..., 255, 255, 255],
       [255, 255, 255, ..., 255, 255, 255]], dtype=uint8)
>>> selection = red < 250
>>> img = np.ones_like(red) * 255
>>> img[selection] = 0
>>> from rasterio.features import shapes
>>> features = list(s[0] for s in shapes(img) if s[1] == 0)
>>> len(features)
4