Re: HTML Canvas - Transforms for HDR and WCG

Thanks for the images.

In the discussion on Monday there was the question of "what happens when an
anonymous PNG such as this image is drawn to an SDR display or into an SDR
canvas?".


In all browsers today, for "Colorbars in HLG 203 display.png", any signal
value above 0.75 is clamped to SDR-white.


Is this the expected behavior when the image is displayed on an SDR display
using an <img> tag?

Is this the expected behavior when it is drawn to an SDR <canvas> element?

Going back to the <img> tag situation, should 0.75 in this image always
match sRGB-white on HDR displays (even if sRGB-white is 80, 100, or 400
nits)?



On Wed, Apr 28, 2021 at 9:32 AM Lars Borg <borg@adobe.com> wrote:

> Enclosed is a set of images in various color spaces, including HDR, with
> ICC profiles.
>
> They all look the same in today’s browsers (tested Safari, Chrome, Firefox)
>
>
>
> These images can be used for validating Chris Cameron’s concepts.
>
> Color matching without ICC profiles will require display-referred
> conversions for HLG.
>
> Please try.
>
>
>
> Lars
>
>
>
> *From: *Lars Borg <borg@adobe.com>
> *Date: *Thursday, April 1, 2021 at 11:52 AM
> *To: *Christopher Cameron <ccameron@google.com>, Simon Thompson <
> Simon.Thompson2@bbc.co.uk>
> *Cc: *"public-colorweb@w3.org" <public-colorweb@w3.org>
> *Subject: *Re: HTML Canvas - Transforms for HDR and WCG
> *Resent-From: *<public-colorweb@w3.org>
> *Resent-Date: *Thu, 01 Apr 2021 21:51:37 +0000
>
>
>
> If you are doing an image browser for arbitrary images and thus arbitrary
> color spaces it would be awkward to have to locate a proper image-specific
> color transform.
>
> Can’t we just use the info that comes with the image?
>
> If blending with text “Buy Now” the blending should be in the same color
> space for all images, or else we would need unique text color values for
> each image.
>
>
>
> Lars
>
>
>
> *From: *Christopher Cameron <ccameron@google.com>
> *Date: *Thursday, April 1, 2021 at 8:13 AM
> *To: *Simon Thompson <Simon.Thompson2@bbc.co.uk>
> *Cc: *Lars Borg <borg@adobe.com>, "public-colorweb@w3.org" <
> public-colorweb@w3.org>
> *Subject: *Re: HTML Canvas - Transforms for HDR and WCG
>
>
>
>
>
>
>
> On Thu, Apr 1, 2021 at 3:35 AM Simon Thompson-NM <
> Simon.Thompson2@bbc.co.uk> wrote:
>
> Hi,
>
>
>
> One further thought from me, the proposal last night depended on using a
> certain image import function which allowed the user to dictate a target
> colour space and transform set.  Does a similar video import function exist?
>
>
>
> Yes! It's the same function, createImageBitmap
> <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FAPI%2FWindowOrWorkerGlobalScope%2FcreateImageBitmap&data=04%7C01%7Cborg%40adobe.com%7C51627b89412443af86db08d8f539c7a8%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C637528975802643088%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=SG%2F3IEUmOUzFfgfZcUj2dVsKuxC97aRKcydTLNL9XvQ%3D&reserved=0>,
> and it takes as input: images, SVG, video, canvas (so you can draw your
> canvas into your canvas), and blob (not-yet-decoded image). The options
> include a "colorSpaceConversion" option, which is currently "none" or
> "default". This is where I think we should consider adding a well-defined
> perceptual colorimetric intent (and this intent wouldn't be
> path-independent).
>
>
>
> When the input is a blob (a not-yet-decoded image), the color space
> conversion can happen simultaneously with image decode.
>
>
>
>
>