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Hi, I've got some jpg images of a horse running. I want to paste them on a tvpaint layer. The thing is, I want to see the background layer (a wood), but the horse images cover everything. I mean, the horse images themselves have a white background that covers the background layer when I paste them. What can I do to make it seem that the horse is running in the wood?

I think it's all about alpha channels, but dunno...

Use Effects->Color->Scan Cleaner. That will transform the white to transparent.

well, have tried, but all i get is more transparency in the whole image - and in some images, nothing changes

Either their is something wrong with your jpg or you messed something in the workflow.
Can you attach one horse-image here ? I will take a look at it and try it.

Another option is to create PNG images with transparency from those JPG files (in Gimp or Photoshop), using the white background as the transparent color, and then import those in to your TVPaint layers. That's probably the easiest thing to do.

the images are a bit heavy to post, but look, now I've done it once, but am not sure how.
Besides, i cannot make the selection marks disappear. why are they still there?
Awww...

Hey, got something! i import the image as a LAYER, then press the magic wand selection button, select the white background and do the scan cleaner thing. It seems to work, but the selection marks won't go!

..Take a look at the Tool-Panel, there is an entry "Clear", press that button. That's all.

if i import these photos as layers, it seems that i can just use the eraser around the horse. i can select the white background and delete it with scan clean or just clear, as you say.
but now the trouble is with those stupid selection marks around the horse - why won't they disappear?
oh, i see, you mean CLEAR from that pannel... thank u!

If they are selection-paths you can clear them in the Tool Settings-Panel.

I wonder about your workflow. I think the easiest way would be:

1. Shift-L (Open)...( into an existing project )
2. select one of your horse.jpg - image sequence
-> now at the Import Panel you should see one of your horses, also the sequence is specified by Mark In and Mark Out.
->Import to new layer
3.The sequence will appear in your timeline
4. Select all images of your horse.sequence in the timeline
5.Use under Top Menu, Image, Basic Scan Cleaner
That should work if your horse is not as white as the background...

imo, the easiest way would be to import your horses sequence in a 32bit format (PNG32 or TGA32),
so you won't import the bg of the source,
if your horses are natively flatten with a white bg, use a luma-key or a color key fx to get rid of the surounding white.

Unfortunately she/he has jpg images. To convert them to png/tga and to give them an additional alpha channel requires some more steps of work. It comes down to do it by hand one by one or to record an photoshop action - or to do keying in one NLE - than you are - eg in TVP.
On a first attempt I would a avoid the extra work.
Scan cleaning is some sort of keying operations. I would give it a first start, and if there is still more to do, the keying methods offered under SFX in TVP are not too bad.
It all depends on color/brightness contrast (and antialias) of your horse/background sequence.