Re: [css-compositing] Additional blend modes

On Sep 14, 2012, at 9:11 AM, Rik Cabanier <cabanier@gmail.com> wrote:

> We've been getting many requests from designers and web developers to add Photoshop's blend modes to the current working draft.
> They felt that these blending modes are commonly used and are needed to achieve certain effects.
> 
> I propose that we extend the current list of blending modes with these values:
> Linear dodge
> Linear burn
> Vivid light
> Linear light
> Pin light
> Hard mix
> Divide
> Subtract
> 
> These blend modes are not in the PDF spec. I checked the open source browsers (and Apple's CoreGraphics) and they don't have an implementation for them which may slow down their adoption.
> If there are no objections, I will update the spec with the blend formulas and example bitmaps.

I'd like to know how often these are used in practice. My (limited) understanding is that the vast majority of cases use a small subset of blending operations. As you mention, we don't necessarily support these at the low-level, which complicates the implementation. I don't want to fill the list for completeness - I'd prefer to have more justification.

This is fairly similar to the idea of adding more canned filter effects - that represent the popular visual designs of today (not 1999 when the filters were first proposed). I'd love to suggest more, but I also want to wait to see how people use the small set we have given them, before being able to argue for expanding the feature.

Dean