How can I do exactly what is in this video?

[Birds2112]

Hey everyone, I posted a question but wasn't able to show my own drawings as examples and now that thread seems to be dead. I'm on a time crunch and trying really hard to figure this out so I'm posting this YouTube video.

https://youtu.be/Ui8q4GwApcw 

What she is doing in her video is exactly what I am attempting to do. I have all the necessary materials. I know how to create an image sequence, I've gotten to that part successfully. When she gets to the part where she describes uploading it and editing in after effects she glosses over what she's actually done and that's the one part I needed detail on. 

Her final animation is colorful hand drawn layers added over each other. Her scans are just pencil on paper drawings, that is also what I have. How can I remove the white underneath the images in the photo sequence and play that sequence over my own footage to give my characters a background? I know I must be missing something here but I'm really at a loss. Nothing I've tried is working. Thank you so much for reading!!

[Mylenium]

The answer was already provided. If you just have b/w line drawings, you can apply an effect like Shift Channels to set transparency based on luminance. For other colors you would use a similar technique, but expand upon it with blending modes or effects like Channel Combiner to generate grey scale images that can be applied as a luma track matte to the original footage. This may also involve other effects to adjust contrast and all that. Not sure what more you need to know. Other than that you can always slap on a keying effect if you don't mind fringing. The simple linear or luminance keyers in the effects may in fact be better suitable than the monstrosity that is Keylight.

Mylenium 

Mylenium 

[Rick Gerard]

Removing the white background on your pencil drawings is as simple as changing the Blend Mode to Multiply. The white will disappear, and the colors below will show up. 

The big challenge is creating the colors and animating their shapes. You will have to do a lot of rotoscoping (animating masks) to add color. I grabbed an Adobe Stock image, added some color correction to make the background whiter, then added a shape layer with a gradient as a background and some solids for the hair, skin, and shirt top. Changing the blend mode of the top sketch layer lets the colors of the other layers show through.

I have attached the AEP file and the Adobe Stock image for you to play with. 

The name of this workflow is Ink and Paint. Depending on your drawings, you may be able to do a little tracking in Mocha AE to speed up the Roto, but just like traditional cell animation, adding the color will take some time.