How can I run image manipulation over each responsive image?

[boryn]

I have set up a conversion with option ->withResponsiveImages(), example code:

$this->addMediaConversion('normalize')
             ->orientation(Manipulations::ORIENTATION_AUTO)
             ->sharpen(8)
             ->contrast(8)
             ->fit(Manipulations::FIT_CONTAIN, 1920, 1920)
             ->withResponsiveImages()
             ->performOnCollections('images');

but actually I would like to add a watermark on each of the responsive images, so that the watermark is clearly visible on each image and not blurred/squeezed, etc. In other words, I do not want to apply the watermark on the "core" image and later resize to responsive images, but I'd rather apply a "crisp" watermark on each responsive image.

Is it possible with the library? Or is there any workaround?