Easiest ACES-CG to SRGB Jpeg?

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Is there a simple, straightforward way to save an image rendered in houdini with ACES color as standard SRGB jpeg without going through another program like Nuke, Fusion, Affinity, etc?

I'm trying to find a way for my coworkers to easily share preview stills with each other over Teams or e-mail, or save WIP stills to document progress. Mplay has the option to export an image with a LUT applied, so maybe that's an option if there is an ACES-CG to Output-SRGB or Output-rec709 LUT. I'm just trying to minimize the steps they need to go through to share quick previews.

Thanks!
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Have a look at "ocioconvert" (comes in the opencolorio package). It's a command line tool to convert textures or other imagery between the colorspaces, it's also useful to mass-ACES'ify textures before converting them to rat for Houdini.
Martin Winkler
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You can setup a vop in cops that does it, there are a few ocio nodes that can convert. If you add some PDG to it you can easily convert batches in parallel for max performance.
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And on a side note: for converting assets into acescg check this: https://vimeo.com/412746848 [vimeo.com]
Edited by Jonathan de Blok - May 15, 2021 01:22:04
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Thanks all,

I'm familiar with the standalone utilities and the OCIO nodes in COPS and MAT. I was hoping for something that doesn't involve extra steps. For example, I can't think of a case where it makes sense to save a .jpg from the render view or mplay in ACES color. Jpeg's, being only 8-bit, can't even properly support ACES. I was hoping maybe there was an option or preference I was missing, or perhaps an ACES-CG to SRGB-2.2 LUT that could be applied on export. If not, maybe this should be RFE?
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BradThompson
I was hoping for something that doesn't involve extra steps.

Ah, apologies, I misread that as "I don't want something extra that costs money" in the first post.
Martin Winkler
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Just set the LUT (in aces folder) in save window instead of using image's color space.
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Thanks Ifree, that's what I was hoping for, but can you elaborate? Which LUT for ACES-CG to SRGB-2.2?
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BradThompson
Thanks Ifree, that's what I was hoping for, but can you elaborate? Which LUT for ACES-CG to SRGB-2.2?

They're all in the aces_1.2/baked/houdini/ folder of your ACES download. I tested it out in COPs using the sRGB for ACEScg Houdini LUT and it works great.
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Easiest way to share a quick image over chat, is to just use snipping tool i would think. In Windows you can use CTRL+Windows+S then mark the location on screen you want to send, then press CTRL+C(copy) and CTRL+V(paste) into the chat. Then done Works like a charm in google chat and other sites/programes that support image pasting.
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Thanks Ifree, that's what I was hoping for, but can you elaborate? Which LUT for ACES-CG to SRGB-2.2?

In folder: aces_1.0.3\baked\houdini, there are some LUTs.
sRGB for ACEScg Houdini.lut or Rec.709 for ACEScg Houdini.lut will be fine for most desktop display.

Refer to the following data.

P3-DCI - Digital Cinema Projector (SDR)
P3-D60 - Digital Cinema Projector (SDR)
DCDM - Digital Cinema Projector (SDR)
DCDM (P3 gamut clip) - Digital Cinema Projector (SDR)
Rec.709 - SDR Broadcast Monitor
Rec.709 (D60 sim.) - SDR Broadcast Monitor
Rec.2020 - SDR Broadcast Monitor
P3-D60 ST2084 (1000 nits) - HDR Broadcast Monitor
P3-D60 ST2084 (2000 nits) - HDR Broadcast Monitor
P3-D60 ST2084 (4000 nits) - HDR Broadcast Monitor
Rec.2020 ST2084 (1000 nits​) - HDR Broadcast Monitor
sRGB - Desktop Computer Display
sRGB (D60 sim.) - Desktop Computer Display
Edited by ifree - May 19, 2021 04:21:20
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Awesome! Thanks. This is exactly what I was hoping for. The screen snip tip is a good one too.

Thanks again!
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Is this possible with karma renderer?

I have the LUT but I can't find the way to specify it when saving a render. Maybe a screenshot could help.

Sorry for the noob question.

Thanks!
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If you right-click your image in view or composite view you can select save as and there you can select the LUT.
when i the LUT, however, the colours are still weird and incorrect
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If you right-click your image in view or composite view you can select save as and there you can select the LUT.
when i the LUT, however, the colours are still weird and incorrect

You might have automatic gamma correction enabled. Make sure "convert to image format's colorspace" is disabled and gamma is 1 when using an ODT lut.

Relying on baked luts to apply an ocio transform isn't always viable. Any custom looks would require baking new luts. They may also lose some precision.

Houdini now ships with oiiotool, which is renamed 'hoiiotool'

use the command line script to apply an ocio display/view transform when converting from scene linear images to display referred images:

hoiiotool -i input.exr --iscolorspace "scene_linear" --ociodisplay "ACES" "sRGB" -o output.jpg
replace input.exr and output.jpg with the actual file names and replace "scene_linear" with the actual input color space if not scene_linear. Use the display and view defined in your config. For example an OCIO 2.1 config might have a display called "Display - sRGB" and view "Output - SDR Video - ACES 1.0"
Edited by jsmack - July 13, 2022 20:32:34
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Houdini now ships with oiiotool, which is renamed 'hoiiotool'

Oh, this is fantastic, thank you! I was just about to ask if I needed to compile OpenColorIO or something, but Houdini saves the day again.
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ifree
BradThompson
Thanks Ifree, that's what I was hoping for, but can you elaborate? Which LUT for ACES-CG to SRGB-2.2?

In folder: aces_1.0.3\baked\houdini, there are some LUTs.
sRGB for ACEScg Houdini.lut or Rec.709 for ACEScg Houdini.lut will be fine for most desktop display.


Could somebody tell how to apply this lut using ffmpeg ?
can not find an option to use it.
ffmpeg gives an error while parsing .lut file...
seems like it can not work with this type of luts
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Any reason to not use hoiiotool?
Edited by TangheStudent - Sept. 1, 2022 18:00:39
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TangheStudent
Any reason to not use hoiiotool?

because it seems like hoiiotool can not convert image sequence to movie
Edited by Nikolay_Skolkov - Aug. 29, 2022 07:30:55
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TangheStudent
Any reason to not use hoiiotool?

because it seems like hoiiotool can not convert image sequence to movie

it's a multi step process. Convert exr (raw render) to video space image sequence that ffmpeg can read (png, jpg, etc) using hoiiotool or cops or ocioconvert. ffmpeg to convert image sequence to movie file. I'm not aware of ffmpeg having good support for exrs, I think they are converted with straight gamma if you use ffmpeg. I wouldn't attempt to use LUTs for aces linear to video conversion, they are bound to have a degree of error. I don't know what luts ffmpeg uses, but it probably can't read Houdini format .lut files.

looks like someone put chocolate in your peanut butter:
https://github.com/jedypod/generate-dailies [github.com]
Edited by jsmack - Aug. 29, 2022 12:40:39
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