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APPENDIX F. CREATING A PERSONALISED LANDSCAPE FOR
STELLARIUM
sections for a mask but it was too fiddly for me. I then used the magic wand tool to
select the sky sections bit by bit (zoom in on the image to see what you are doing)
this would have been easy if the sky had been cloudless because colour match does
this selection. I cut each selection out. It took about an hour to remove all the sky
(because it was cloudy) and leave just the skyline image as a suitable mask. Clicking
the magic wand in the sky area when all the sky has been removed will show an outline mask of the removed sky. Zoom in and carefully check the whole area to make
sure there is no sky left. Leave this mask there.
4. Re-select the alpha channel and turn the other channels off. The alpha channel will
be visible and the mask should be showing. Re-select Edit in Quick mask mode and
then Edit in standard mode to edit. Select the brush tool and toggle to the black
foreground. Fill in the masked area with a large brush size. The colour (black) will
only go into the masked area. It wont spill over so the job is quite easy.
5. When this is done you will have created your alpha layer. Check the size of the image
and if it is greater than 5000 pixels wide reduce its size by a fixed percentage till it is
under this limit. The limit was necessary for one of the programs I used but may not
be always necessary. However any greater resolution will be wasted and the file size
will be excessive. Save the whole image in the compressed tiff form or PNG form.
The only formats that preserve the alpha channel.
6. This image is the horizon picture. Give it a name .tif or .png, whichever format you
save it in.
After making the panorama.tif I noticed that the trees still had areas of the
original sky embedded that werent blanked by the alpha layer. I found that I could
add these sections piece by piece to the alpha layer with the magic wand and paint
them out. This took some time, as there were a large number to be removed. However
the result was worth the effort, as it allows the sky display to be seen through the
trees. Especially at high zooms ins.
Another little trick I discovered was that the panorama could be saved as a JPEG file
(no alpha channel) and the alpha channel also saved as a separate JPEG file. This can
save space for transmission. And allow manipulation of the original file in another
program as long as the skyline is unchanged. At a later date the two files can be
re-combined in Photoshop to re-form the TIFF file with alpha channel.
Using this trick I did a little patching and painting on the original picture in Paint on
the original JPEG form. When completed I loaded it into Photoshop and added the
blank alpha channel to it. I was then able to paste the previously created alpha layer
into the new picture. It worked perfectly.
7. The panorama now needs to be broken up into suitable square images for insertion
into a landscape. It took me some time to get the hang of this but the process I found
best was in The Gimp. It was the easiest to cut the main panorama into sections as it
has a mask scale in the tool bar.
8. Load the panorama file with alpha channel into The Gimp. Then using the mask
tool cut out the squares of the predetermined size starting from the left hand side of
the picture. I don’t think it is necessary to make them exact squares but I did not
experiment with this aspect. The position of the cut will be shown on the lower tool
bar. Accuracy is improved if you use the maximum zoom that will fit on the page.
9. Create a new picture from the file menu then select and adjust the size to your predetermined size then select transparent for the background. Because of the alpha
channel the transparent section will be automatically clipped of much of the transparent part of the picture. Paste the cutting into the new picture. If it is smaller
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