X PixMap (XPM) is an image file format used by the X Window System, created in 1989 by Daniel Dardailler and Colas Nahaboo working at Bull Research Center at Sophia Antipolis, France, and later enhanced by Arnaud Le Hors.

It is intended primarily for creating icon pixmaps, and supports transparent pixels. Derived from the earlier XBM syntax, it is a plain text file in the XPM2 format or of a C programming language syntax, which can be included in a C program file.

The "symbolic" feature permits adjusting colors depending on the context where they are used. Code such as <code>s border c blue</code> could be adjusted on a blue background.

Many-color encoding

One tool is known to use only a to p for 16 colors, switching to aa up to dp for 64 colors, but still reading single character encodings for 64 colors; compare Base64.

With more colors the codes use more characters, e.g. aa up to pp for 16 × 16 = 256 colors. This is less useful for text editors, because a string ab could be actually the middle of two adjacent pixels dabc. Spaces are allowed as color code, but might be a bad idea depending on the used text editor. Without control codes, backslash, and quote (needed in XPM1 and XPM3) 128 − 33 − 2 = 93 ASCII characters are available for single character color codes.

Simplified example: 90 US-ASCII characters could be arranged into nine non-overlapping sets of 10 characters. Thus unambiguous strings of nine characters could set the color of each pixel by its XPM palette index with up to 10<sup>9</sup> = colors (compare to GIF, which supports only 256).

For XPM2 it is clear how many lines belong to the image – two header lines, the second header line announcing the number of color codes (2 lines in the example above) and rows (height 4 in the example above), e.g. 2 + 2 + 4 = 8 lines.

XPM3

The current and last format is XPM3 (1991). It re-introduces the C wrapper, but instead of explicitly showing a file's structure, the strings stored are essentially identical to XPM2.

<syntaxhighlight lang="C">

/* XPM */

static char * XFACE[] = {

"48 4 2 1",

"a c #ffffff",

"b c #000000",

"abaabaababaaabaabababaabaabaababaabaaababaabaaab",

"abaabaababaaabaabababaabaabaababaabaaababaabaaab",

"abaabaababaaabaabababaabaabaababaabaaababaabaaab",

"abaabaababaaabaabababaabaabaababaabaaababaabaaab"

};

</syntaxhighlight>

If the "values" line contains six instead of four numbers, the additional values indicate the coordinates of a "hotspot", where 0 0 is the upper left corner of a box containing the icon and the default. A "hotspot" is used for mouse pointers and similar applications.

Comparison with other formats

right|thumb|Blarg file opened in program window

The following code displays the same blarg file in the XBM, XPM and PBM formats.

XBM version:

<syntaxhighlight lang="C">

  1. define test_width 16
  2. define test_height 7

static char test_bits[] = {

0x13, 0x00, 0x15, 0x00, 0x93, 0xcd, 0x55, 0xa5, 0x93, 0xc5, 0x00, 0x80,

0x00, 0x60 };

</syntaxhighlight>

right|thumb|Blarg.xpm (XPM2) rendered by XnView

XPM2 version:

<pre>

! XPM2

16 7 2 1

  • c #000000

. c #ffffff

  • ..*...........
  • .*.*...........
  • ..*..**.**..**
  • .*.*.*.*.*..*.*
  • ..*..**.*...**

...............*

.............**.

</pre>

XPM3 version:

<syntaxhighlight lang="C">

/* XPM */

static char * blarg_xpm[] = {

"16 7 2 1",

"* c #000000",

". c #ffffff",

"**..*...........",

"*.*.*...........",

"**..*..**.**..**",

"*.*.*.*.*.*..*.*",

"**..*..**.*...**",

"...............*",

".............**."

};

</syntaxhighlight>

PBM file:

<pre>

P1

16 7

1 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0

1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0

1 1 0 0 1 0 0 1 1 0 1 1 0 0 1 1

1 0 1 0 1 0 1 0 1 0 1 0 0 1 0 1

1 1 0 0 1 0 0 1 1 0 1 0 0 0 1 1

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0

</pre>

Application support

ACDSee, Amaya, CorelDRAW, GIMP, ImageMagick, IrfanView (formats plugin), PaintShop Pro, PMView, Photoshop (plugins), and XnView among others support XPM. Gravatar also supports XPM.

An X11 libXpm vulnerability was fixed in 2005, and three more in 2023.

FFmpeg version 3.3 or later can decode XPM.

See also

Notes

References

See also

  • X Window System (X11) and X11 color names
  • <abbr title="portable bitmap">PBM</abbr> (mono), <abbr title="portable graymap">PGM</abbr> (grayscale), <abbr title="portable pixmap">PPM</abbr> (color), <abbr title="portable anymap">PNM</abbr> (any)
  • X BitMap
  • libXpm - X Pixmap (XPM) image file format library