saitoha/libsixel — pull request #1 by saitoha (2014-04-17 16:46:50+00:00)
Title: Experimental support for 1bpp PNG

@ttdoda reported that the following command is failed.

```
curl -s http://mail.iwmt.org/~sue/tmp/sn.png | img2sixel
```
This patch fix it.