I have some comments on Bhaaluu's onion-skinning tutorial which is
included at the end of this message.
Step 9 instructs the user to perform a "File->Open" the second frame
(f_000002.xcf). When using GAP, you should not use File->Open to
navigate frames; use one of the commands: "Video->Go To" (which is
useful to assign keyboard shortcuts), "Video->Playback" (which
provides some nice "scrubbing" functionality), or "Video->VCR
Navigator" (which provides easy cut-n-pasting of frames). Not only
will the operation take much less time, but some operations depend
upon GAP managing the displays. Step 9 should instruct "Video->Go
To->Next Frame".
In Step 8, the Stack Position line should have a "0" in it; specifying
that the onionskin layer should be placed at the top of the layerstack.
Stack Position: 0 [From Top]
In Step 10, the onion-skin layer should appear above the background
layer in the layerstack and it should be unnecessary to lower it (if
the instructions in the preceding comment are followed).
In Steps 11 to 14, it would probably be better to use the Move Tool to
align the layers, rather than the Selection Tool. The method that
Bhaaluu proposed will only work with older versions (2.2 and earlier)
of GIMP, whereas using the Move Tool works with all versions. The Move
Tool permits the keyboard cursor keys to be used for moving in
single-pixel increments (or SHIFT-cursor for larger steps). This also
eliminates the need to make a selection and the need to anchor the
layer.
Instead of performing Steps 15 and 16, just move on to the next frame.
Because the onionskin setup includes the "Auto delete before saving",
the XCF file which gets saved (before you go to a different frame)
will not have the onionskin layer. After you are done with all of your
editing, delete the onionskin configuration, and use the
"Video->Frames Convert..." command to save your results as PNM files.
In Step 17, again "File->Open" should not be used. To navigate to the
second frame, use one of the methods suggested in my first comment.
Finally, the instructions of Step 19 suggest that using onionskin
layers is not the best approach for this task. Onionskinning is useful
if you want to align frame 2 with frame 1, frame 3 with frame 2, frame
4 with frame 3, and so on. It is not a particularly good method to
align frame 2 with frame 1, frame 3 with frame 1, frame 4 with frame
1, etc.
I would propose the following approach to accomplish the latter task
(the first seven steps are identical to Bhaaluu's tutorial):
1. Create new directory and save all PNM files to the new directory.
2. Change to the new directory, and create a directory: PNM
3. Copy all the PNM files to the PNM directory. This is a backup.
4. Open The Gimp.
5. File > Open > f_01.pnm
6. Video > Frames Convert...
Extension: .xcf
GAP saves all the PNM files as XCF files, in sequential order.
7. Close f_01.pnm.
8. In f_000001.xcf window, perform an "Image->Duplicate". A new
"Untitled" image should be displayed.
9. In f_000001.xcf window, perform a "Video->Move Path". Change the
Stepmode to "None" and change the Opacity to "50%" (the From and To
frames should be the first and last frames). Press OK. -- this will
create a copy of the first frame as the top layer of each of the frames.
10. Perform a "Video->Go To->Next frame". (You should assign this
command to a keyboard shortcut. I have assigned my F5, F6, F7, and F8
keys to First, Previous, Next, and Last frame commands respectively.)
11. Activate the bottom layer ("Layer->Stack->Select Bottom Layer").
This is conveniently accomplished with the END key.
12. Activate the Move Tool (keyboard shortcut "M"). Hold down the
SHIFT key and use the mouse to align your registration points (or use
the cursor keys)
Repeat Steps 10 through 12. This amounts to the following keystrokes:
F7, END, cursor keys and should be rather quick to accomplish. If it
is necessary to use the Rotate Tool, you will have to anchor the
floating layer.
13. Go to the first frame ("Video->Go To->First Frame")
14. Perform a "Video->Frames Layer Delete" and delete "layerstack:
0" from the first to the last frame (leaving only your background).
15. Perform a "Video->Frames Convert..." as in Step 6, only change
the extension to ".pnm".
The GAP is rather intimidating at first; but it can be a powerful tool
for accomplishing repetitive image editing tasks, not just animations.
--------------------------------------------------------
==============================
== START OF QUOTED TUTORIAL ==
==============================
On Thu, 23 Oct 2008, Bhaaluu wrote:
Recently, I asked a question about how to use the Onionskin feature
of the Gimp Animation Package. The following is a Summary of what I
did to align a series of drawings that had registration crosshairs
with the crosshairs on the first drawing, so all the drawings would
be registered with each other. The drawings were all scanned into
the computer using a flatbed scanner. All the drawings were saved
as PNM image files from the scanner. The directions I was given were
good for onionskinning a drawing with the one right behind it in
numerical order. I slightly modified those instructions to align all
62 drawings with the very first drawing.
1. Create new directory and save all PNM files to the new directory.
2. Change to the new directory, and create a directory: PNM
3. Copy all the PNM files to the PNM directory. This is a backup.
4. Open The Gimp.
5. File > Open > f_01.pnm
6. Video > Frames Convert...
Extension: .xcf
GAP saves all the PNM files as XCF files, in sequential order.
7. Close f_01.pnm.
8. In f_000001.xcf window:
Video > Onionskin > Configuration...
Reference Mode: Normal
Onionskin Layers: 1
Frame Reference: -1
Stack Position: [X] From Top
Opacity: 50.0 / 100.0
Select Mode: All Visible (ignore pattern)
[X] Auto create after load
[X] Auto delete before save
Click [Okay]
9. File > Open > f_000002.xcf
10. In the Layers window, make sure the onionskin_000001 layer is above
the Background layer otherwise, the onionskin effect can't be seen.
I used the down arrow in the Layers window to move the Background
down one. That will make the onionskin appear.
11. Lasso both drawings.
12. View > Zoom to whatever magnification you need to align the cross-
hairs. I used 200%.
13. With the mouse cursor inside the lassoed area, press the mouse
button and drag until the crosshairs are aligned.
14. Click outside of the lassed area to anchor the drawing.
15. Right click the onionskin_000001 layer in the Layers windows and
Delete Layer. Clean up drawing with eraser, or whatever.
16. Save the file.
17. File > Open > f_000002.xcf
18. Move the Background under the onionskin layer in the Layers window.
19. Video > Onionskin > Configuration...
Frame Reference: -2
Click [Okay]
What this does is makes the first drawing the reference drawing.
On each new drawing I open, I will move the Background below the
onionskin layer, and change the Frame Reference in the Onionskin
Configuration. The next change will be to -3, then -4, and so on.
Each time this is done, new onionskin layers are built for the
remaining files, so this may not be good if you have 1000's of
drawings. It wasn't so bad with only 62 drawings.
20. Follow steps 11 to 16.
I make videos for YouTube with PPM files, so I did a Save As... after I
saved each XCF file, and saved a PPM copy of the registered image of
the drawing in a PPM directory as I went along. Likewise, I organize
the other files in the same way: XCF files go in a XCF directory, etc.
I found out that if a drawing was cocked, I could first align the
crosshairs, then use the rotate tool with the center placed on the
aligned crosshairs, to uncock it. My experience doing this has
convinced me that attaching a pegbar to the scanner is the best
way to solve the problems I experienced. This is my first flatbed
scanner, so I'm learning things the hard way..
Many thanks to "saulgoode" for the expert instructions that allowed me
to use The Gimp GAP Onionskin tool to do exactly what I wanted to do!
I believe that what I am posting is correct to the best of my knowledge.
Your mileage may vary. I am not responsible for how you use this info,
nor for any damage which may directly or indirectly occur as a result
of you using this info. Best of luck in all your Gimp-GAP adventures!
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