- From: Leonard Rosenthol <lrosenth@adobe.com>
- Date: Wed, 27 Jan 2021 22:24:42 +0000
- To: Lars Borg <borg@adobe.com>, Justin Novosad <junov@google.com>, Chris Lilley <chris@w3.org>
- CC: "public-colorweb@w3.org" <public-colorweb@w3.org>
- Message-ID: <87344B6E-C73F-47EB-908E-32E90AB236C8@adobe.com>
I would say that pretty much every content authoring tool – be it graphics (Photoshop, Inkscape, Scribus) or documents (MSOffice, GDocs, PDF, etc.) uses gamma/non-linear blending – though also in SDR. To change that in the web space (at least for SDR content) would also require a change of all of those authoring tools or users won’t be able to author content that matches. I do agree, however, that in the context on HDR content it may well make sense to consider alternatives since the authoring isn’t there yet…. Provided that we fully describe a mixed SDR/HDR stack and how compositing would work in such a scenario – especially when multiple colorspaces are also involved… Leonard From: Lars Borg <borg@adobe.com> Date: Wednesday, January 27, 2021 at 2:23 PM To: Justin Novosad <junov@google.com>, "chris@w3.org" <chris@w3.org> Cc: "public-colorweb@w3.org" <public-colorweb@w3.org> Subject: Re: Pre-meeting Thoughts on HDR Canvas Resent-From: <public-colorweb@w3.org> Resent-Date: Wednesday, January 27, 2021 at 2:23 PM It is easy to assume that blending in gamma space is always undesirable. History tells a different story. Blending in non-linear space is common. For example, in Photoshop you can select to blend in linear or non-linear space. It’s a creative choice. It seems most users select the non-linear option. AFAIK video fades are typically in code space, not linear space. So it seems we should retain this option. Lars From: Justin Novosad <junov@google.com> Date: Wednesday, January 27, 2021 at 7:59 AM To: Chris Lilley <chris@w3.org> Cc: "public-colorweb@w3.org" <public-colorweb@w3.org> Subject: Re: Pre-meeting Thoughts on HDR Canvas Resent-From: <public-colorweb@w3.org> Resent-Date: Wednesday, January 27, 2021 at 7:59 AM Thanks Chris for correcting me. I realize this is an old problem, but I think that adding HDR capabilities to canvas risks exacerbating it greatly because we will end up with inconsistent blending and gradient interpolation based on the canvas's working profile. For example, if a hypothetical app selects a canvas working profile to match the output device's capabilities, these behavior discrepancies risk being perceived as bugs and will be unpleasant to work around for web developers. On Wed, Jan 27, 2021 at 12:46 PM Chris Lilley <chris@w3.org<mailto:chris@w3.org>> wrote: On 2021-01-27 18:32, Justin Novosad wrote: > The CSS and SVG specifications do not explicitly address the issue of > gamma-correct blending, but the examples in the CSS spec suggest doing > things the "wrong" way, which ignores gamma correctness. The SVG specification explicitly says that filer operations are in linear-light sRGB by default (with an option to change to sRGB, where speed is more important than getting the right result); and that all other operations are (sadly) in gamma-encoded sRGB by default (with an opt-in for linear-light sRGB). The CSS Compositing specification, sadly, requires operations in gamma-encoded sRGB. This choice was primarily driven by backwards compatibility with existing content; and secondarily with compatibility of blend modes, as popularized in Adobe Photoshop, which are also computed in gamma-encoded RGB spaces. CSS Compositing thus needs to add an opt-in for linear-light compositing. -- Chris Lilley @svgeesus Technical Director @ W3C W3C Strategy Team, Core Web Design W3C Architecture & Technology Team, Core Web & Media
Received on Wednesday, 27 January 2021 22:37:52 UTC