Thank you for clarifying. We tried to reproduce the issue with image rendering after conversion html file to the pdf file with different image types and all time image was rendered well for us. Could you please share with us example of the html file that you use for conversion. Also will be helpful if you share example of your code which you use for conversion that we can check and fix it for you.
As for natively coded API – sorry but this information is internal information which we should not share with the customers.
If you will have more questions please feel free to contact us.