NWA-PCUG Newsletter Article, July 2011
Panoramas using GIMP
By Cal Esneault,
President and leader of many Open Source Workshops & SIGs,
Cajun Clickers Computer Club, Louisiana
February 2011 issue, Cajun Clickers Computer News
http://www.clickers.org
http://cccclinuxsig.pbwiki.com
cjesne (at) bellsouth.net (click to email author)

Small point-and-shoot cameras are great to carry around on vacation. However, due to the smaller geometry and limited angular response of digital sensors, wide-angle shots are limited. One solution is to take slightly overlapping shots and combine them during post-processing into a single scene. Below are two photos I took from a hill overlooking a scenic harbor. Even at the widest setting, I was not able to capture the whole scene.

GIMP is a sophisticated open-source photo editing tool which is available as a free download for most operating systems (Windows, Linux, Mac OS). To create panoramas, however, you have to download a plug-in called Pandora. Once you have it installed, you find it as the last item in the Filters menu (see screenshot). Clicking on this item will open an image loading dialog from which you select the pictures you want to merge (the two pictures I selected are circled). Upon opening the image files, you will find that they are on multiple layers, and Pandora has automatically shifted the images so that they are aligned. This is not always perfect, so you may have to select one of the images and shift it using the Move tool.

The recommended procedure for panoramas is to determine the exposure, match this exposure in manual mode, and then take all pictures at the same setting. Unfortunately, my simpler camera didnt allow for this, so the auto-exposure for each picture was slightly different. Any exposure variance is readily seen when the pictures are super imposed. Using the GIMP brightness control for one of the layers, I could easily adjust the picture to have uniform exposure for both layers.

GIMP saves pictures in a native .xcf format. Prior to exporting this image to the more conventional .jpg format, I had to Merge the Layers and Flatten the image.

Then, using Save As, I gave the picture a name with the jpg suffix (a conversion tool is embedded in the program, and you can adjust the picture quality for saving).

Below is the final panorama shot showing the much broader view. Making panoramas is a good way to get these wide shots without having to carry around a much heavier DSLR. It takes a little practice, but the technique is within the scope of most users.

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