[ILUG] Merging (JPG) Images

[David Neary]

John A. Kinsella wrote:
> Hi.
> No doubt a DAQ (dumb ass question) but here goes.
> I've scanned a map so I can play with my GPS. Trouble is that the map is
> too big to scan in all at once so I scanned it in an A4 page at a time.
> 
> Tried to use the Gimp to assemble the pieces into a single image (using
> copy/paste) but Gimp just overlays pasted piccy on top of target. When I
> try to move pasted image to appropriate position it gets clipped as
> outside viewport.

Layers & Channels, man!

1) Open first image (I'll assume all the images are the same
dimensions. Further, for the purposes of having real figures I'll
assume that size is 400x600).
2) Add Alpha Channel (very handy later).
3) resize canvas (Image->Canvas Size) to nxm times as big (as big
as is required for the images you have) - unlink the Ratio entry
boxes if you need to.
4) Judicious use of guides. Set guides at x=400, x=800, x=1200,
etc... and y=600, y=1200, y=1800, etc... If you don't know, you
get a guide by clicking on the ruler along the side and dragging
down the image. Very handy for bounding selections & the like.
5) Load the next image. Copy it, and paste it into the original
(now expanded) image. In the layers & channels dialog, make sure
you create it as a new layer.
6) Making sure Snap to guides is on (it should be by default, if
not it's a toggle in the View menu), select the new layer, and
the Move tool (the arrows), and move the new layer to the place
you want it. It should snap nicely to the guides.
7) While (not finished), goto 5. If rewuired, re-expand the
canvas.
8) When finished, save as...

> I'm sure there is a simple way of doing it - any suggestions?

See above. 

> A similar problem occurs when I rotate an image - there nust be a way to
> increase viewport size?

Ctrl-e will resize the window to the optimal size for the current
image. Then there's 2 different things you're talking about - the
viewport size (which is just the size of the window), and the
canvas (image) size, which is the (virtual) bounding box of the
image. Then there's the 3rd different thing, the layer size,
which (to avoid unnecessary use of memory) isn't necessarily the
same size as the image, unlike photoshop.

Hope this helps,
Dave.

-- 
       David Neary,
    Marseille, France
  E-Mail: bolsh at gimp.org