KNOW HOW Panoramas Perfect Panoramas with Hugin, Enblend, and Autopano-SIFT 360 Degree View You can create a pleasing image by aligning multiple landscapes to form a panorama. But the alignment can be tricky, especially if the individual photos do not match.Tools like Hugin, Enblend, and Autopano-SIFT help you create that perfect seamless panorama. BY OLIVER FROMMEL f you have more pictures than you problems start. It is difficult to achieve Free software can help correct this can fit in one image, you may wish to soft and invisible seams. Normally, pho- kind of distortion, align the individual Itry the old trick of combining multi- tos are so distorted that it is impossible images, and finally, mount the images to ple digital photographs into a pleasing to correct them manually. The lens is create a panorama. wide-angle view. But you’ll find it diffi- partly to blame; lenses typically distort cult to combine these photos into a images, turning straight lines to curves Equalizing and Aligning seamless image using just the Gimp. that make photo composition difficult. Photos This article discusses some alternative The other reason is the distortion The Hugin [2] graphics program displays tools that you can use to automatically caused by shooting a series of pictures. If the images, allowing the user to select adjust and align images. These tools will you remain stationary and turn the cam- neuralgic points for equalizing and align- help you create seamless panoramas era left and right, the objects on the right ing the images. from separate photographs. of the image will appear too big, The program is easy to install, but it It’s easy to take a series of digital pho- whereas the objects on the left appear requires a few libraries that some distrib- tos for a panorama, but this is where the too small. utions do not include. Check out the “Installation” box for more details on the Box 1: PanoTools install. For a long time, the PanoTools package was Because the program’s author,Helmut GLOSSARY the only free software for creating Dersch,no longer has the software on his panoramic images.The PanoTools license own homepage,other people are offering Roll,Pitch and Yaw are all terms for spatial conditions have always been complex.The the old packages. In fact, there are even rotation about three axes. Roll describes a library and PTOptimizer are released under some commercial offshoots,although they rotation about an axis perpendicular to the the free GNU Public License,whereas various may not be quite legal. A Sourceforge project image plane,pitch is the rotation about a licenses apply to some of the individual has since been founded to maintain the free horizontal axis,yaw is the rotation about the programs. parts of PanoTools [1]. vertical axis. 48 February 2005 www.linux-magazine.com Panoramas KNOW HOW Box 2: Installation Hugin needs the WxWidgets library from complaining about a missing package Debian does not have additional wxGTK (formerly WxWindows) and the WxWidgets- because the package dependencies are packages that include “xrc” in the package XRC extension. Most distributions include wrong.The workaround involves specifying names; look out for libwxgtk2.4-contrib-dev the other required libraries,such as Libtiff, an RPM program option to disable the instead. You can use the following dependency check: LibPNG,and LibJPG. Besides the FFTW math commands to install the required libraries, package,Hugin also needs the Boost Library, rpm -iv --nodeps hugin-0.4-cvsU LibPano, and Hugin (both of which are on the if you intend to build Hugin yourself. 20041021.bp.fc2.i386.rpm DVD with this issue): Unfortunately, the version and name depend apt-get install libwxgtk2.4-dev U on the distribution. For example, the Boost Although Suse has a version of WxWindows developer library for Fedora is simply called by default,Hugin cannot use the default. libwxgtk2.4-contrib-dev fftw2 U libboost-devel; Debian users need three Thus,you will need to remove the existing dpkg-i libpano12_20040917-1_i386. packages called libboost-graph-dev,libboost- package and use the Fedora packages deb dev and libboost-python-dev. instead – don’t worry, this worked fine with dpkg-i hugin_0.4pre20040917-1_i U Suse 9.1 in our lab: 386.deb The required files for Fedora are located in a U subdirectory on the DVD.The following com- rpm -iv panorama-tools-2. Whether this will work or not depends on mand installs the libraries: 7a-1.i386.rpm wxGTK-xrc-2.4.U the software and libraries you have installed 2-4.1.fc2.dag.i386.rpm fftw-2.1.U previously.If you are still missing a package, rpm -iv panorama-tools-2.7a-1.U 3-1102.i586.rpm hugin-200409U you might like to try googling for the pack- i386.rpm wxGTK-* fftw2-* 21-1.bp.fc1.i386.rpm wxGTK-2.4.U age name and required package format.The The Panorama tools include libpano12,but 2-4.1.fc2.dag.i386.rpm boxes for Autopano and Enblend give you this does not stop the package manager more detail on the requirements. After you type hugin to launch the pro- The second tab, Camera and Lens, is Manual Control Points gram, the main window shown in Figure for correcting optical distortion caused Hugin needs a few definitive image 2 appears. Click on Add individual by the camera and lens. If your images details to be able to align two adjacent images… to select individual images. In include EXIF information, Hugin can images correctly. The Control Points tab the dialog that appears, you can hold automatically extract the required data. handles this. The tab shows you two down [Ctrl] and click to select multiple If you do not know the angle of view for images, allowing you to click on signifi- images. your lens, refer to Table 1 (extracted cant points to create assignments. Hugin displays a list of images in the from PanoTools documentation). First, set up Hugin to display two adja- panel on the left, adding some details, The Inherit switch allows all the other cent images by setting the number in the such as the width and height; the rota- images to inherit the settings from the tab above the right-hand image one tional values (Yaw, Pitch, Roll) are also current image. If you disable this setting, higher than the left-hand tab (Figure 3). displayed, although they default to zero. the program can handle images with In other words, if both are 0 when you Hugin uses the first photo as a reference different distortion values. After discov- start, you need to set the right-hand tab point for aligning the other images. The ering the best values for your camera (by to 1. You can then use the arrow keys to “Anchor this image …” button allows trial and error), you can store these val- flip through the images, and Hugin will you to select another image as the refer- ues under Lens Management and load show you consecutive images on the left ence point. them for your future Panorama projects. and right. Figure 1: Loading the individual images in the Hugin main window. Figure 2:The Camera and Lens tab. www.linux-magazine.com February 2005 49 KNOW HOW Panoramas Figure 3: Hugin displays two adjacent images, allowing the user to select Figure 4:The Optimizer tab supports granular control of the optimization image details as control points. values automatically set by Hugin. You will want to check auto fine-tune Anchor) option for the Optimizer, and Optimizer, you can manually set the val- and auto-estimate, as this tells Hugin to then click Optimize now!. The three text ues for each image – this is a setting for help you assign the control points. auto boxes below display the image number experts. add tells the program to add each and the value by which Hugin needs to The Preview in the bar at the top gives mapped pair at the specified points – you correct the individual image, following you a preview with the calculated val- can do this manually by clicking the Add the square brackets with or without a ues. You might want to select Auto in the button. checkmark. If an image is not checked, preview window to tell the program to If you have enough points, you can this means that Hugin will not be modi- show you the latest results. switch to the number crunching part by fying it, which is the case with the clicking Optimizer (Figure 4). Check the reference image (Anchor). If you select Mounting Images Positions (pairwise optim., starting from the Custom parameters below for the The final tab, Stitcher, is the heart of the program – and the biggest challenge at Box 3: Mono for Autopano the same time; things don’t always work Autopano-SIFT is written in the C# program- mount -t binfmt_misc none /proc/U out as expected. Stitching is the process ming language and needs the Mono project sys/fs/binfmt_misc of putting multiple images together to create a panoramic image. libraries [3].To use the software,you do not Finally,you need to tell the kernel how need the complete Mono environment.You to recognize Mono files and launch This process typically implies aligning do need the interpreter,which runs the pro- mono. the images and correcting distortion gram,and a few libraries.The Suse packages echo ':CLR:M::MZ::/usr/bin/mono:' U beforehand. Hugin supports two so- are mono-core-1.0.2-1.ximian.9.1.i586.rpm, > /proc/sys/fs/binfmt_misc/register libicu26-2.6.2-1.ximian.9.0.i586.rpm,gtk- Assuming that your exe files are executable Box 4: Enblend sharp-1.0.2-1.ximian.9.2.i586.rpm, (chmod +x),you can now launch them The Enblend package [6] does not need any- libgtkhtml3.1_7-3.1.13.0.200405120525- directly.You still need to unpack Autopano- thing special in the line of libraries,apart 0.snap.ximian.9.1.i586.rpm.