Fix trouble with pngs

cat.py

@@ -16,3 +16,4 @@ def cat(w, h):
 if __name__ == "__main__":
     cat = cat(1920,1080)
     cat.show()
+

pixelflut.py

@@ -57,7 +57,7 @@ with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
     for w in widthlist:
         if rnd: np.random.shuffle(heightlist)
         for h in heightlist:
-            color = '#%02x%02x%02x' % pixels[h-starth][w-startw]
+            color = '#%02x%02x%02x' % pixels[h-starth][w-startw][0:3]
             to_send = "px {} {} {}\n".format(w,h,color)
             sock.sendall(bytes(to_send, "utf-8"))
     sock.close()