pamstack

Stack the planes of the specified PAM images in the specified order

$ pamstack [path/to/image1.pam path/to/image2.pam ...] > [path/to/output.pam]

$ pamstack [[-t|-tupletype]] [tuple_type] [path/to/image1.pam path/to/image2.pam ...] > [path/to/output.pam]

pamstack [-horz] [netpbmfile ...]

-horz
    Concatenates images horizontally instead of vertically. By default, images are stacked vertically.

netpbmfile
    Specifies an input Netpbm image file. Multiple files can be listed. If - is used as a filename, pamstack reads from standard input. All input images must have the same width (or height if -horz is used), maxval, and tuple type.

pamstack is a utility from the Netpbm image processing suite designed to vertically concatenate multiple Netpbm images into a single output image. It takes two or more input images, either specified by filename or read from standard input. A fundamental requirement for all input images is that they must possess identical widths, maximum color values (maxval), and tuple types (e.g., grayscale, RGB, RGB_ALPHA). The command outputs the combined image to standard output, making it easily pipeable to other Netpbm tools or redirected to a file. This function is particularly useful for creating vertical panoramas, assembling sequential image frames, or simply consolidating several smaller images into one larger, scrollable graphic. As part of Netpbm, pamstack adheres to the suite's philosophy of simple, atomic operations that can be chained together for complex image manipulations.

pamstack imposes strict requirements on its input images: all images must share identical widths (or heights when using the -horz option), the same maximum color value (maxval), and an identical tuple type (e.g., all grayscale, all RGB, all RGB_ALPHA). Failure to meet these criteria will result in an error and the command will terminate.

The resulting stacked image is always written to standard output. This design choice facilitates piping the output directly into other Netpbm utilities for further processing or redirecting it to a file using shell redirection.

pamstack is a component of the comprehensive Netpbm image processing toolkit, which evolved from the PBMPlus package developed in the late 1980s. The command's functionality is very similar to, and in some contexts, considered interchangeable with, the pamcat utility. This overlap suggests that pamstack might represent an earlier iteration or a specialized variant of vertical/horizontal image concatenation within the Netpbm suite, likely developed around the time the flexible PAM format became a cornerstone of the library.

pamcat(1), netpbm(1)