Picture This

Most users probably get the feeling that Bama isn't useful for working with images because they either connect with a simple telnet program, or they connect indirectly with a mail client using IMAP or POP. We have several pieces of software to aid in working with images. Some of these require that you have X-Windows running for viewing, but there is also a package of programs that aids in image manipulation. Documentation is currently very sparse for these routines, but we'll be developing more for presentation on the Web in the near future.

Image Manipulation

We have installed a package of software called netpbm. This software contains programs that convert from a wide variety of formats to a simple standard and can convert from that standard to other formats. This gives you great flexibility to convert between image formats.

The image standards are called pbm, pgm, and ppm for portable bitmap, graymap, and pixmap, respectively. A bitmap is a black-and-white representation, a graymap adds shades of gray, and a pixmap has color information. There is also a generic representation called pnm where the "n" stands for any of "b", "g", or "p". Some of the well-known image formats that can be worked on include "TIFF", "GIF", Window (PC) bitmap, X11 bitmap or pixmap, Sun rasterfile, SGI image file, and PostScript. There are over 70 supported formats in all.

Once your image has been put into the standard it can be manipulated in a variety of ways, such as being flipped, rotated, scaled, smoothed, as well as having more sophisticated operations done on it involving the image properties. There are more than 60 routines available.

There are also a few routines that are useful for people developing web sites. These are "giftrans", "webgif", and "whirlgif". The "giftrans" program can take a color in a gif image and make it transparent. There is more help for this in the man pages. Type

man giftrans

The "webgif" program can also set a color to be transparent in a gif image, but it is more useful for creating an interlaced gif file. These are the files you see on the web where the entire image seems to appear at once but is not very clear at first. As time goes by and the web server transfers more information the image comes up to its final appearance. To get help with "webgif" just type its name alone on the line (followed by "enter", of course).

The "whirlgif" program can make animated gifs out of a series of individual gif images. Again, documentation on this is in short supply, but it you type the command "whirlgif" alone, it will tell you more about what you are supposed to do with it.

Image Viewing

Almost all the image-viewing programs require that you have X-Windows running on your PC or that you are working directly on a Unix workstation.

xv: XV is the famous image-viewing program written by John Bradley at the University of Pennsylvania. We have the program loaded now for personal, non-work-related personal "amusement" (i.e. it is unregistered shareware). This means you can use it to fiddle around with images, say in relation to your web site, but you cannot use it for work or for a class. If this usage statement changes, the information will be made available on the Unixinfo software Web page http://bama.ua.edu/~unixinfo/software/software.html

imagetool: Imagetool can be used to view gif, tiff, jpeg and PostScript files. It gives you some basic manipulation such as rotation, and flipping. This program works best when run on a more robust X-Windows system and doesn't seem to like some of the PC X-windows programs.

snapshot: This is can display a few simple image types but cannot manipulate them. It can display gif and Sun rasterfile images. Its main use is to make an image out of some portion of the screen. Note that this must be an X-Windows portion of the screen. You cannot take a snapshot of your PC application. Snapshot is going to suffer some of the same problems as Imagetool because it uses Imagetool to display. However, it is still able to take a snapshot of your X-window and save it for later use.

Any Web browser: If the image you want to view is under your "public_html" file tree, then you can view it with any web browser, provided it is a supported format, that is. But this does include gif, tiff, and jpeg images. So, if your image is labeled "my_vacation.gif" and it is located in "public_html", you can view it by pointing your web browser to:

http://bama.ua.edu/~userid/my_vacation.gif

where "userid" is your Bama user name. You won't be able to manipulate the image, but if you have been using another program to get images ready for the web, you'll certainly get the view that the rest of the world is getting. Of course, you don't need an X-windows web browser to do this; any one will do.

© 1999, The University of Alabama. The information included here is for the University of Alabama central computing facility as it was configured on the document date. It may or may not apply to other Unix systems.

February 15, 1999 Vol. 3 Index Back to Vol. 3, No. 5 Ahead to Vol. 3, No. 7		Search:

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	Picture This Most users probably get the feeling that Bama isn't useful for working with images because they either connect with a simple telnet program, or they connect indirectly with a mail client using IMAP or POP. We have several pieces of software to aid in working with images. Some of these require that you have X-Windows running for viewing, but there is also a package of programs that aids in image manipulation. Documentation is currently very sparse for these routines, but we'll be developing more for presentation on the Web in the near future. Image Manipulation We have installed a package of software called netpbm. This software contains programs that convert from a wide variety of formats to a simple standard and can convert from that standard to other formats. This gives you great flexibility to convert between image formats. The image standards are called pbm, pgm, and ppm for portable bitmap, graymap, and pixmap, respectively. A bitmap is a black-and-white representation, a graymap adds shades of gray, and a pixmap has color information. There is also a generic representation called pnm where the "n" stands for any of "b", "g", or "p". Some of the well-known image formats that can be worked on include "TIFF", "GIF", Window (PC) bitmap, X11 bitmap or pixmap, Sun rasterfile, SGI image file, and PostScript. There are over 70 supported formats in all. Once your image has been put into the standard it can be manipulated in a variety of ways, such as being flipped, rotated, scaled, smoothed, as well as having more sophisticated operations done on it involving the image properties. There are more than 60 routines available. There are also a few routines that are useful for people developing web sites. These are "giftrans", "webgif", and "whirlgif". The "giftrans" program can take a color in a gif image and make it transparent. There is more help for this in the man pages. Type `man giftrans` The "webgif" program can also set a color to be transparent in a gif image, but it is more useful for creating an interlaced gif file. These are the files you see on the web where the entire image seems to appear at once but is not very clear at first. As time goes by and the web server transfers more information the image comes up to its final appearance. To get help with "webgif" just type its name alone on the line (followed by "enter", of course). The "whirlgif" program can make animated gifs out of a series of individual gif images. Again, documentation on this is in short supply, but it you type the command "whirlgif" alone, it will tell you more about what you are supposed to do with it. Image Viewing Almost all the image-viewing programs require that you have X-Windows running on your PC or that you are working directly on a Unix workstation. xv: XV is the famous image-viewing program written by John Bradley at the University of Pennsylvania. We have the program loaded now for personal, non-work-related personal "amusement" (i.e. it is unregistered shareware). This means you can use it to fiddle around with images, say in relation to your web site, but you cannot use it for work or for a class. If this usage statement changes, the information will be made available on the Unixinfo software Web page http://bama.ua.edu/~unixinfo/software/software.html imagetool: Imagetool can be used to view gif, tiff, jpeg and PostScript files. It gives you some basic manipulation such as rotation, and flipping. This program works best when run on a more robust X-Windows system and doesn't seem to like some of the PC X-windows programs. snapshot: This is can display a few simple image types but cannot manipulate them. It can display gif and Sun rasterfile images. Its main use is to make an image out of some portion of the screen. Note that this must be an X-Windows portion of the screen. You cannot take a snapshot of your PC application. Snapshot is going to suffer some of the same problems as Imagetool because it uses Imagetool to display. However, it is still able to take a snapshot of your X-window and save it for later use. Any Web browser: If the image you want to view is under your "public_html" file tree, then you can view it with any web browser, provided it is a supported format, that is. But this does include gif, tiff, and jpeg images. So, if your image is labeled "my_vacation.gif" and it is located in "public_html", you can view it by pointing your web browser to: http://bama.ua.edu/~userid/my_vacation.gif where "userid" is your Bama user name. You won't be able to manipulate the image, but if you have been using another program to get images ready for the web, you'll certainly get the view that the rest of the world is getting. Of course, you don't need an X-windows web browser to do this; any one will do. © 1999, The University of Alabama. The information included here is for the University of Alabama central computing facility as it was configured on the document date. It may or may not apply to other Unix systems.
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