Bug 215896 – CSS invert() and opacity() filter implementations should use linear transfer functions for clarity and simplicity

• Component: CSS
• Status: RESOLVED FIXED

In WebKit's implementation of CSS filters invert() and opacity(), FEComponentTransfer is used and the transfer function is surprisingly to table, instead of linear. Looking at the CSS spec, https://drafts.fxtf.org/filter-effects/#invertEquivalent
invert() and opacity() is implemented using "table" with just 2 values, which is equivalent to using a linear function. I propose to change the implementation of invert() and opacity() to use linear transfer function as well for simplicity and clarity.

[Radar WebKit Bug Importer]

<rdar://problem/67887069>

Created attachment 407421 [details]
Patch

[Darin Adler]

Comment on attachment 407421 [details]
Patch

Does this have any effect on performance?

(In reply to Darin Adler from comment #3)
> Comment on attachment 407421 [details]
> Patch
> 
> Does this have any effect on performance?

No, not that I know of. By looking at the code, FEComponentTransfer eventually converts linear, discrete table transfer functions to a hash map that maps each R,G,B values to a new value by applying the transfer function. So I don't expect this patch to cause any performance hit at all

[EWS]

Committed r266266: <https://trac.webkit.org/changeset/266266>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 407421 [details].