added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng
added some helpful comments and the i0 shell param for optipng