$ pamdice myimage.ppm -outstem=myimage_part -width=10 -height=8
$ pamundice myimage_part_%1d_%1a.ppm -across=10 -down=8 >myimage.ppm
$ pamundice myimage.ppm myimage_part_%2a -across=13 -hoverlap=9
You can use the minimum unique abbreviation of the options. You can use two hyphens instead of one. You can separate an option name from its value with white space instead of an equals sign.
This program is part of Netpbm.
pamundice reads a bunch of Netpbm images as input and combines them as a grid of tiles into a single output image of the same kind on Standard Output.
You can optionally make the pieces overlap.
The images can either be in files whose names indicate where they go in the output (e.g. "myimage_part_03_04" could be the image for Row 3, Column 4 - see the input_filename_pattern argument) or listed in a file, with a -listfile option.
The input images must all have the same format (PAM, PPM, etc.) and maxval and for PAM must have the same depth and tuple type. All the images in a rank (horizontal row of tiles) must have the same height. All the images in a file (vertical column of tiles) must have the same width. But it is not required that every rank have the same height or every file have the same width.
pamdice is the inverse of pamundice. You can use pamundice to reassemble an image sliced up by pamdice. You can use pamdice to recreate the tiles of an image created by pamundice, but to do this, the original ranks must all have been the same height except for the bottom one and the original files must all have been the same width except the right one.
One use for this is to process an image in pieces when the whole image is too large to process. For example, you might have an image so large that an image editor can't read it all into memory or processes it very slowly. You can split it into smaller pieces with pamdice, edit one at a time, and then reassemble them with pamundice.
Of course, you can also use pamundice to compose various kinds of checkerboard images, for example, you could write a program to render a chessboard by computing an image of each square, then using pamundice to assemble them into a board.
An alternative to join images in a single direction (i.e. a single rank or a single file) is pamcat. pamcat gives you more flexibility than pamundice in identifying the input images: you can supply them on Standard Input or as a list of arbitrarily named files.
To join piecewise photographs, use pnmstitch instead of pamundice, because it figures out where the pieces overlap, even if they don't overlap exactly vertically or horizontally.
To create an image of the same tile repeated in a grid, that's pnmtile.
pnmindex does a similar thing to pamundice: it combines a bunch of small images in a grid into a big one. But its purpose is to produce an index image of the input images. So it leaves space between them and has labels for them, for example.
Unless you use a -listfile option, there is one non-option argument, and it is mandatory: input_filename_pattern. This tells pamundice what files contain the input tiles.
pamundice reads the input images from files which are named with a pattern that indicates their positions in the combined image. For example, tile_00_05.ppm could be the 6th tile over in the 1st rank, while tile_04_01 is the 2nd tile over in the 5th rank.
You cannot supply any of the data on Standard Input, and the files must be the kind that pamundice can close and reopen and read the same image a second time (e.g. a regular file is fine; a named pipe is probably not).
input_filename_pattern is a printf-style pattern. (See the standard C library printf subroutine). For the example above, it would be tile_%2d_%2a.ppm. The only possible conversion specifiers are:
The number between the % and the conversion specifier is the precision and is required. It says how many characters of the file name are described by that conversion. The rank or file number is filled with leading zeroes as necessary.
So the example tile_%2d_%2a.ppm means to get the name of the file that contains the tile at Rank 0, File 5, you:
Note that this pattern describes file names that pamdice produces, except that the precision may be more or less. (pamdice uses however many digits are required for the highest numbered image).
In addition to the options common to all programs based on libnetpbm (most notably -quiet, see Common Options), pamundice recognizes the following command line options:
Default is 1.
Default is 1.
There must not be any input image narrower than this.
Note that this undoes the effect of the same -hoverlap option of pamdice.
Default is zero -- no overlap.
The named file contains file name, one per line. Each file contains the image for one tile, in row-major order, top to bottom, left to right. So the first file is the upper left tile, the second is the one to right of that, etc. The number of lines in the file must be equal to the number of tiles in the output, the product of the -across and -down values.
The file names have no meaning to pamundice. You can use the same file multiple times to have identical tiles in the output.
This option was new in Netpbm 10.90 (March 2020).
pamundice was new in Netpbm 10.39 (June 2007). Before that, pamcat is the best substitute.