chroma key with mask?

Schmacker wrote on 9/26/2019, 12:42 PM

Is it possible with the image below to chroma key just the white screen so I can show my power point slides that I have placed as a background. I've tried several methods of masking in an attempt to only apply the chroma key to the screen portion but it still seems to apply to the entire image.

Comments

yvon-robert wrote on 9/26/2019, 1:18 PM

Hi,

you have just to resize your PowerPoint movie or slide picture to fit on the screen using position and size tool plus 3d rotation, slant around the axes. With mask is much more difficult to do.

Regards,

Schmacker wrote on 9/26/2019, 1:27 PM

I have the slide positioned and sized as needed. What I can't seem to figure out is how to apply chroma to just the screen portion of the image.

terrypin wrote on 9/26/2019, 1:43 PM

Hi,

Do you mean a result like this?

Or is it to be a movie, with the presenter/lecturer moving in front of the projector screen?

Terry, East Grinstead, UK

Schmacker wrote on 9/26/2019, 2:13 PM

it is a movie, but if I could do what you did with the single image I THINK it would work for the movie since the projector screen is motionless.

terrypin wrote on 9/26/2019, 2:16 PM

But does he walk in front of the projector screen?

Schmacker wrote on 9/26/2019, 2:20 PM

yes, at times, but rarely.

I had a version working where I just placed the slide in front of the movie, but then thought it would be better as a background and therefore considered the chroma key effect for exactly the reason of walking in front of the screen.

terrypin wrote on 9/26/2019, 2:34 PM

OK, I can't test it without a lot of work but I'm hopeful that the method I used for my static example should work for a movie. Here are the steps I took:

Put your movie in track 3 instead of my image and see how that looks.

Schmacker wrote on 9/26/2019, 7:01 PM

didn't work. slides image is in front of me walking in front of screen.

Any other ideas? I feel like adding a mask effect should work when applying the chroma to the movie but I can't get it to only chroma just the projector screen even though that is where I have applied a mask.

I've gotten the Chroma key effect to work, somewhat, as you can see in the attached image. However, its applied to the entire movie, not just the masked area.

terrypin wrote on 9/27/2019, 4:59 AM

I've gotten the Chroma key effect to work, somewhat, as you can see in the attached image. However, its applied to the entire movie, not just the masked area.

Did you make the mask as I showed, with Alpha assigned? It looks like you have assigned black or white.

browj2 wrote on 9/27/2019, 7:32 AM

@Schmacker

Hi,

Assuming that the screen stays white throughout, try putting the original on track 1 and moving presentation and the modified original with chromakey white down to tracks 2 and 3 or higher. So long as the presentation is resized down, the black that shows up due to the chromakey will now see the original video.

Otherwise, the only other way to do this is to rotoscope it, making a animated resizing mask using Xara from MEP. This can take a lot of time, especially if you move a lot and the presentation is long. See my tutorials on this.

John CB

terrypin wrote on 9/27/2019, 10:33 AM

@Schmacker

I don't have your video so I made my own MP4 (simulating the screen obstruction with a moving block) and by applying John's neat suggestion this was the result:

I haven't fine-tuned the slide image position and deformation but otherwise it seems to do the job.

Here's the detail:

Terry, East Grinstead, UK