Need improvement on the "copy current channel to clipboard" function (Ctrl+C) of the VFB

[mathieu_boch]

Hello,

We are switching our pipeline to ACES. Everything is good for rendering and compositing, but we're having trouble about reviewing. We use lot of "screenshots" to show renders with color correction, but the alpha isn't stored in the "copy current channel to clipboard" function (Ctrl+C).
When we save the VFB in png (save current channel) , we need to check the save profile in image and change the gamma (boring), and the png is ok in chaos player but not in web page or windows viewer...
Please can you add the option to save alpha channel in the ctrl+c. This feature might be very usefull for us.

Thank you

[^Lele^]

You are using a mix of color-manged and non-color managed applications, thereby you see stuff in the wrong way.
The alpha channel *is* copied along with the channel data.
It's the pasting (i.e. the target applications) being the issue, just as the issue is with these applications with the viewing.

Proof the image has alpha, using a clipboard viewer:

Original image



As it is in memory after copying.
Notice the BG has gone white to signify a hole, and the unpremultiplied edges are visible.

[mathieu_boch]

Ok, the alpha is stored in the clipboard, but when I paste in a web tool, I lose it. We want to be able to paste premultiplied image without using any software between ctrl+c and the ctrl+v. Like the capture tool of windows in freeform, when I paste, it's premultiplied.

[mathieu_boch]

When I compare the clipborad content, I saw that thee VFB is a bitmap and not a png unlike I paste it.

[^Lele^]

I have had a chat with the devs about the way we go about this.
The QImage object is used, in a way that stores the raw ARGB data at 8 bits per channel.
The image is not premultiplied, and the Alpha channel is reduced from the internal 3-channel width via an Intensity operation.
The QImage is the Qt object for image management - it can handle various formats - but the way it's used by us is to store raw image data.

It's down, then, to the receiver of the buffer to make choiches: consider the alpha channel, premultiply the RGB with it, and so on.

What you can see from the clipboard viewer below (on the left-hand side) are the formats the raw data could be pasted into, as the Windows OLE expects, but it does not mean the data is stored as any of those formats, just that this application can enumerate the available options correctly, something that apparently can't be said for all the application you are using.
We can't currently see any way we could change this on our side, unfortunately, to cater for your specific scenario.
My personal suggestion would be for you to use applications that can deal with raw buffers, and are color managed (ideally OCIO), otherwise you're going to have a field day after the other trying to gauge ACES material.

[mathieu_boch]

Ok thank you for your quick answer. I'll see what can I deal with my devs