*sigh*
…I found more variants.
- oxipng --opt max --strip all --nc “$original_image” --out “$path_to_oxi_nc_output”
- --nc: Preserve the original image’s colour type (e.g. RGB(A), grayscale, or indexed colours).
- Listed as the “Oxi-NC” entry.
- oxipng --opt max --strip all --nc --zopfli “$original_image” --out “$path_to_oxi_nc_zf_output”
- Listed as the “Oxi-NC-ZF” entry.
Results for the ‘section-series.png’ image, with the best-to-worst encoding order being: CWebP, Oxi-NC-ZF, Oxi-NC, PNGQuant or OxiPNG or OxiPNG-ZF or Oxi-Quant or Oxi-ZF-Quant, then Original.
Filename: 'section-series.png'
Original Filesize: 197 bytes
PNGQuant Filesize: 160 bytes
OxiPNG Filesize: 160 bytes
OxiPNG-ZF Filesize: 160 bytes
Oxi-Quant Filesize: 160 bytes
Oxi-Quant-ZF Filesize: 160 bytes
Oxi-NC Filesize: 158 bytes
Oxi-NC-ZF Filesize: 156 bytes
CWebP Filesize: 86 bytes
Smallest encoding: 86 bytes, CWebPWanna know the worst part? It’s not a one off result. In fact, it actually improved four images in terms of the smallest PNG encoding possible.
All original input images use the RGB(A) colour type.
And yes, the --nc --zopfli variant can lose to the --nc variant, so we need both.