[nSLUG] Gimp help? (Re: Image utility for Linux?)

Daniel Morrison draker at gmail.com
Wed May 16 00:43:31 ADT 2007

On 15/05/07, Mike Spencer <mspencer at tallships.ca> wrote:

> Here's my problem:
>     + Working with two PGM images, A & B, that have substantial overlap,
>     + Open image A in a Gimp window

>     + Open image B (same height but narrower, overlaps A) in another
>       Gimp window

I think the problem is right here, where you open a second window, copy
and then paste "a floating layer" into the first window.  I believe your
problem is that you never deal with the floating layer that is created.
By "deal with" I mean either "anchor" it into the current layer, or more
likely, make into a new layer in it's own right.  Notice in the Layers
dialog that the floating layer has not got a 'mini' image of itself,
rather the content that is floating appears in the 'mini' image of the
current layer (I think, the layer immediately below the floating layer).

Select 'Layers -> Anchor layer' if you're happy with the position of the
floating selection and you want it merged into the current layer.  But
portions of the floating selection which are off the current layer will
get cropped out - _even_if_ you have done 'fit canvas to layers'. Or...

Select 'Layers -> New Layer' to convert the floating layer into its own
layer.  Now you can move it around some more, and when you're satisfied,
'Image -> Fit Canvas to Layers' and then either Flatten image or Merge
Down (these commands will be 'un-grayed' as soon as you've dealt with the
floating layer).

>     - The "Display navigation" window shows exactly what I want but the
>       main, A window shows a checker board where the overlaid B image
>       is larger than the original A image.

I'm not sure what the "display navigation" window is, but I think what
you're describing is the same as what I was saying above (the 'floating
layer' is cropped outside of the current layer).

>     - The "Layer->Anchor layer" option doesn't produce the desired
>       result.

which is I think the same thing again; you are losing part of the floating
layer image.

NOW!  Maybe it would be better to avoid all that opening windows, copying,
pasting, and making new layers from floating selections.  Instead, after
initially opening Image A, rather than opening Image B in a second window,
choose from Image A's 'File' menu -> 'Open as layer' to open Image B.
Image B will immediately become a proper layer in Image A's window, which
you can then move around, fit canvas to layers and merge down.

Another trick, if you already have two image windows open: intead of
select all & copy/paste, just open the layers dialog (Ctrl-L) for one
image (say Image B).  Now drag the representation of the layer from the
layers dialog onto the other image window (Image A) and hey presto, the
layer of Image B is tranferred into the window of Image A.  You can close
the Image B window and continue working in the Image A window.

Just be careful: there is only one Layers dialog, no matter how many
windows you have open.  The Layers dialog will switch to show the layers
of whichever window your cursor is in.  This can get annoying sometimes,
when you open a window, mouse over to the layers dialog and accidentally
pass over another gimp image window on the way over.

Hope this helps; if anything isn't clear just say so!

Oh yes, in case you don't know already, in the Layers dialog you can
reduce the opacity of the currently selected layer.  You might find this
very handy in getting the overlap correct.  Just don't forget to restore
the opacity to 100% before you merge down.

If you really want to get fancy, you can use the colour gradient tool in a
layer mask to gradually 'fade out' one layer, and another, opposite layer
mask to 'fade in' the second layer. This might help blur little
inconsistencies that you couldn't quite match up using scale and
perspective tools.  If you want pointers for that I can write more detail,
but only the basics, I'm not actually very good at it... :)


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