image optimizer for web

pingo v0.99.2 shows that the following 3 switches are available for brute-forcing lossless optimizations:
-sa
-sb
-sc

These are designated by -sN [a-c] when running pingo without any arguments.

However, pingo -sc  doesn't work. pingo returns "bad command".

Also, for whatever reason, looks like typing a word surrounded by the "less than" and "greater than" signs (as if the word was an HTML) tag, is removed in comments and replaced with white space. I would suggest keeping the reply text as-is and instead converting potentially exploitable characters to their HTML entity equivalent.

In the previous example, the text was supposed to read:

pingo -sc  [filename]

Where "[" is "".

Hmm, I did not know there is experimental lossless bruteforce option.

- how to enable above mentioned option it in PINGA?
- how to force lowest priority in PINGA?
- for some reason PINGA has superb efficiency regarding big files, but small files like 5kb are often optimized by other software even 10%-90% further. I wonder why.