Re: Compositing math in SVG

About HDR, the problem is they can take values bigger than 1.
Let's say I have two HDR images with values in range 0-4.
Do I first map the range 0-4 to 0-1, do the blend math, and go
back to 0-4? Do I just do the math on the range 0-4 and
then clamp?

I am rereading the SVG docs, and I am not sure if the
general compositing formula implies that I should implement
all combinations of porter-duff operations and blend modes?
Or I should just use 'src_over' for blend modes and have
a separate function for each of the porter-duff operations?

I mean do you need to use any other porter-duff operation
with blend modes? Does it make sense to do for example
screen(blend mode) and in(porter-duff)?