Hi there, first excuse my engish. (french below)
Im trying to do lightpaiting in real time with, Purr Data, a webcam and a raspberry pi 4 . I've seen some videos about it but i really dont know how it works.
I've found a patch that could works, but i've got white trails instead of the real colors.

Do you know if there is a trick to keep the color? or should i use the patch for inspirate myself and create a new one ?

How do you learn PD when you are new and trying a new project ? I mean before find this patch, i was trying randoms commands to get the trails without success. I'd never thought using things like [separator] or [pix_buffer] etc...
thanks a lot for helping

Bonjour!

J'essaye de faire du lightpainting en temps réel avec Purr Data une webcam et un raspberry pi4. J'ai vu des vidéos avec l'effet que je recherchais mais je n'arrive pas à comprend comme ca fonctionne.
J'ai trouvé un patch qui pourrait marcher, mais la couleur de reste pas. Je n'ai que du blanc au lieu d'avoir la couleur de la lumière ( rouge sur la photo ).
Est ce qu'il y a une petite astuce qui me permettrait de garer la couleur d'origine? Je ne sais pas si je dois garder ce patch ou essayer d'en créer un nouveau en m'inspirant de celui la , si c'est un bonne piste ou pas!

Et mon autre question, comment vous débuter dans PD ? Avant d'avoir trouver ce patch, j'ai essayer pas mal de truc mais sans trop savoir ce que ça allait faire, et sans résultat du coup. Jamais il ne me serai venu a l'idée d'utiliser [separator] ou encore [pix_buffer]

Merci beaucoup ..je commence à désespérer

It's an intensity thing, rather than a GEM issue -- either the LEDs are too bright, or the automatic exposure in the webcam is compensating for the overall darker background.

Of course you want the video dark, relative to the LEDs. Ideally, you'd have a video camera with manual settings.

@Olka If @gmoon is right (probably is) you could try [pix_contrast] just after [pix_video]
It might help.......... or there might be a control panel for the camera that you can access by sending the message......... dialog
into [pix_video]....... see the pix_video help file by right clicking it and selecting help.
David.

Thanks both of you

I've tried to modify the darkness with the control panel for the camera, and also minimize the bright LED. I have also tried to do it in complet dark room but the colour are still remplaced by the white trails.
If i use [dialog], I've got some nice options about seetings camera, but its unclickable. I dont know why.

I have tried with a
old cam usb
then
a camlink with a go pro
and
camlink with 2 differents camera ( sony hx90v & lumix FZ82)

Maybe its unclickable because of first webcam is too old or camlink not good..

One way to tell it's a camera issue is the (imperfect) specular reflection on your wooden table -- the LED light reaching the camera from that reflection has the "correct" intensity and plenty of color saturation.

Simple auto-exposure for cameras works by averaging all the tones and adjusting exposure to achieve a "medium gray" overall. If your camera is auto-exposure only, that's a problem -- you need a dark background, but the camera will always lighten the scene (try to average it out to gray).

Does the GoPro work? Those should have manual exposure settings in the camera.

Otherwise, try what whale-av mentioned (and [color 0.25 0.25 0.25] and [pix-threshold] with high values), but those solutions are destructive, data-wise.

@Olka And a bright light from the front would help reduce the contrast...... by "from the front" I mean from behind the camera (without causing a shadow from the camera...... so above/below/to the side.
David.