Image Processing Reference
3.13.2 Cross-Fading Part 2—Assembling
Images composed of several distinct shots are often called
panoramic photos. You can shoot such images freehand.
Unfortunately, panoramic photos often suffer from horizontal
or vertical mismatches, distortions, or canted sides. If you use
a tripod when shooting panoramic photos, it will be easier to
combine the images. In any event, make certain that about
one-third of each image can overlap onto the other images so
that the dissolve will appear natural and smooth. It is extremely
important to use the same focal distance and depth of focus
when taking the photos. If you don't, you'll end up with a
disjointed, odd-looking panorama made up of parts that just
don't fit together.
Depending on the model and focal depth of the lens,
your images might have distorted edges. You might have to
adapt the images with additional transformations to enable
the stitching process. Although this is a delicate venture, it is
possible with GIMP.
The pictures for the example exercise were taken with a
telephoto lens and a single-lens reflex (SLR) camera. They are
predominately free of distortions.
The Set Image Canvas Size window with the
recommended settings for our example
When combining photos into
panoramic images, prepare them
first so that they are all the same size
and, more importantly, the same
resolution. Many digital cameras
offer a panorama function as an aid
for taking such pictures.
• Open the Garda1.png image in the subfolder Gardapanorama in the
SampleImages folder on the DVD.
• In the Layers dialog, add an alpha channel to the Background layer. This
will add transparency attributes to the layer, including the ability to
reposition the transparency or other objects. Just right-click to open the
context menu and select Add Alpha Channel .
• In order to stitch the images together, you must expand the image
window. Enlarge the image surface to the right. Select Image > Canvas
Size and enter a width of 80 in and a height of 19 in.
• Match the image to the canvas size by selecting the View > Zoom > Fit
Image in Window menu item.
• Position the Garda1 layer with the Move tool to approximately the center
of the left edge of the canvas.
• Save the image as gardapanorama.xcf .