add blend modes to watermark
It would be great to add blend modes to the watermark that affect only on how the watermark is projected onto the image. In fact, that is the behaviour expected when I switched on blending in this module.
<houz> blendmodes don't set how the watermark is rendered on the image, but how the (image+watermark) is mixed with (image)
While the current behaviour as describe by houz is useful in most modules, in this module it might be more intuitive for the user to make blending apply to how (watermark) is mixed with (image) instead.