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This program is part of Netpbm.
ppmsvgalib displays a PPM image on a Linux virtual console using the Svgalib facility. Svgalib is a popular means of displaying Graphics in Linux without the use of the X Window System. (To display a Netpbm image in an X window, see pamx).
If you run ppmsvgalib with a version of Svgalib earlier than 1.9, you must run it with CAP_SYS_RAWIO capability (on most Linux systems, that means you run it as superuser), because Svgalib uses the ioperm() system call to access the console hardware. Newer Svgalib has its own device driver, so you need only proper permissions on a device special file to access the console.
ppmsvgalib is not capable of using color mapped video modes. These are the old video modes that are usually called "8 bit" color modes.
ppmsvgalib is a bare displayer. It won't do any manipulation of the image and is not interactive in any way. If you want a regular interactive graphics viewer that uses Svgalib, try zgv (not part of Netpbm).
To exit ppmsvgalib while it is displaying your image, send it a SIGINTR signal (normally, this means "hit control C").
ppmsvgalib draws a white border around the edges of the screen. It does this to help you isolate problems between the image you're displaying and the facilities you're using to display it.
(Note: if the image you're displaying reaches the edges of the screen, it will replace the white border).
ppmsvgalib places the image in the center of the screen.
If your image is too big to display in the video mode you selected, ppmsvgalib fails. You can use pamcut to cut out a part of the image to display or use pamscale to shrink the image to fit.
If you want to play with ppmsvgalib, ppmcie is a good way to generate a test image.
To be pedantic, we must observe that ppmsvgalib displays a PPM image in the correct colors only if the display has a transfer function which is the exact inverse of the gamma function that is specified in the PPM specification. Happily, most CRT displays and the modern displays that emulate them, are pretty close.
Running the PPM image through pnmgamma can help cause ppmsvgalib to display the correct colors.
In practice, there are probably only two modes you'll ever care about: 25 is the standard SVGA direct color mode, which is 1024 columns by 768 rows with 8 bit red, green, and blue components for each pixel and no fancy options. 28 is the same, but with the popular higher resolution of 1280 x 1024.
But if you have an older video controller (with less than 4MB of memory), those modes aren't available, you might like mode 19, which is 640 x 480 and takes less than a megabyte of video memory. This is a standard VGA video mode.
By Bryan Henderson, January 2002.
Contributed to the public domain.