gif [ -39cdektv ] [ file ... ]
png [ -39cdektv ] [ file ... ]
ppm [ -39cdektv ] [ file ... ]
bmp [ file ]
v210 [ -39cdektv ] [ file ... ]
yuv [ file ]
togif [ -c comment ] [ -l loopcount ] [ -d msec ] [ -t transindex ] [ file ... [ -d msec ] file ... ]
toppm [ -c comment ] [ file ]
topng [ -c comment ] [ [ -g gamma ] [ file ]
ico [ file ]
toico [ file ... ]
The default behavior of jpg , gif , and ppm is to display the file , or standard input if no file is named. Once a file is displayed, typing a character causes the program to display the next image. Typing a q , DEL, or control-D exits the program. For a more user-friendly interface, use page (1), which invokes these programs to convert the images to standard format, displays them, and offers scrolling, panning, and menu-driven navigation among the files.
These programs share many options:
-e Disable Floyd-Steinberg error diffusion, which is used to improve the appearance of images on color-mapped displays, typically with 8 bits per pixel. Primarily useful for debugging; if the display has true RGB color, the image will be displayed in full glory.
-k Convert and display the image as a black and white (really grey-scale) image.
-v Convert the image to an RGBV color-mapped image, even if the display has true RGB color.
-d Suppress display of the image; this is set automatically by any of the following options:
-c Convert the image to a Plan 9 representation, as defined by image (6), and write it to standard output.
-9 Like -c , but produce an uncompressed image. This saves processing time, particularly when the output is being piped to another program such as page (1), since it avoids compression and decompression.
-t Convert the image, if it is in color, to a true color RGB image.
-3 Like -t , but force the image to RGB even if it is originally grey-scale.
Jpg has two extra options used to process the output of the LML video card:
-f Merge two adjacent images, which represent the two fields of a video picture, into a single image.
-F The input is a motion JPEG file, with multiple images representing frames of the movie. Sets -f .
The togif and toppm programs go the other way: they convert from Plan 9 images to GIF and PPM, and have no display capability. Both accept an option -c to set the comment field of the resulting file. If there is only one input picture, togif converts the image to GIF format. If there are many files , though, it will assemble them into an animated GIF file. The options control this process:
-l loopcount By default, the animation will loop forever; loopcount specifies how many times to loop. A value of zero means loop forever and a negative value means to stop after playing the sequence once.
-d msec By default, the images are displayed as fast as they can be rendered. This option specifies the time, in milliseconds, to pause while displaying the next named file .
Gif translates files that contain a `transparency' index by attaching an alpha channel to the converted image.
Ico displays a Windows icon (.ico) file. If no file is specified, ico reads from standard input. Icon files contain sets of icons represented by an image and a mask. Clicking the right button pops up a menu that lets you write any icon's image as a Plan 9 image (widthxheight.image), write any icon's mask as a Plan 9 image (widthxheight.mask), or exit. Selecting one of the write menu items yields a sight cursor. Move the sight over the icon and right click again to write.
Toico takes a list of Plan 9 image files (or standard input) and creates a single icon file. The masks in the icon file will be the white space in the image. The icon file is written to standard output.
http://www.w3.org/Graphics/JPEG/itu-t81.pdf
http://www.w3.org/Graphics/GIF/spec-gif89a.txt
http://www.w3.org/TR/2003/REC-PNG-20031110
http://netpbm.sourceforge.net/doc/ppm.html
http://en.wikipedia.org/wiki/Windows_bitmap
http://en.wikipedia.org/wiki/Yuv