Dark mode support

[chernandezq]

Hi, thanks for your awesome package, how I can modify the background color when the user click on save because I changed the background color to black but the image saved return with black background and this image is added to a document (blank page) so, the image uploaded has black color and I it doesn't seem good. how I could create a copy of this image with background blank and pencil color black, do you understand me?

[YanYuanFE]

please provide your code example