Feature Request: Choose background color when compressing PNGs

[Miguel-Dorta]

Hi! I think it'd be cool if you could define other background color for transparencies when compressing from PNG. For example, in the options object, set the attribute "backgroundColor" to "#ffffff".

Thank you for reading!

[chrismclarke]

I'm guessing this might be linked to the following issue on compress.js: alextanhongpin#3, which they say in the readme is a known limitation (so not sure how likely it is to be fixed)