X PixMap

History

XPM1

The first (1989) XPM format is relatively similar to the XBM format. Compared to XBM, it uses additional macro definitions and variables for indexed colors, and replaces bits with characters for describing the image. The following is a black-and-white image in the 1989 XPM format.

#define XFACE_format 1
#define XFACE_width 48
#define XFACE_height 48
#define XFACE_ncolors 2
#define XFACE_chars_per_pixel 1
static char *XFACE_colors[] = {
"a", "#ffffff",
"b", "#000000"
};
static char *XFACE_pixels[] = {
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
// and so on for 48 rows with 48 pixels

XPM2

XPM2 (1990) simplifies the format by removing all C code. The structure is simplified to ! XPM2

• The value section describes the overall dimension of the image similar to the #define statements.
• The color section defines the values, and a new concept of the "type" of the color. The types may be c for "color", m for "monochrome" output, g for "grayscale", and s for "symbolic", explaining what a defined color is supposed to do.
• The pixels and optional extensions remain as in the original format.

The above file, with width 48, height 4, 2 colors, and 1 character per pixel, becomes:

! XPM2 48 4 2 1 a c #FFFFFF b c #000000 abaabaababaaabaabababaabaabaababaabaaababaabaaab abaabaababaaabaabababaabaabaababaabaaababaabaaab abaabaababaaabaabababaabaabaababaabaaababaabaaab abaabaababaaabaabababaabaabaababaabaaababaabaaab

Colors

In addition to hexcodes, the colors can be any of the X11 color names. In addition, None indicates transparency.

The "symbolic" feature permits adjusting colors depending on the context where they are used. Code such as s border c blue 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 109 = 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.

/* XPM */
static char * XFACE[] = {
"48 4 2 1",
"a c #ffffff",
"b c #000000",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab"
};

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

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

XBM version:

#define test_width 16
#define test_height 7
static char test_bits[] = {
0x13, 0x00, 0x15, 0x00, 0x93, 0xcd, 0x55, 0xa5, 0x93, 0xc5, 0x00, 0x80,
0x00, 0x60 };

XPM2 version:

! XPM2 16 7 2 1

• c #000000 . c #ffffff
  • ..*...........
• .............
  • ..*.....**
• ........*
  • ....**....** ...............* .............**.

XPM3 version:

/* XPM */
static char * blarg_xpm[] = {
"16 7 2 1",
"* c #000000",
". c #ffffff",
"**..*...........",
"*.*.*...........",
"**..*..**.**..**",
"*.*.*.*.*.*..*.*",
"**..*..**.*...**",
"...............*",
".............**."
};

PBM file: 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

Application support

ACDSee, Amaya, CorelDRAW, GIMP, ImageMagick, IrfanView (formats plugin), PaintShop Pro, PMView, Photoshop (plugins), and XnView among others support XPM.{{cite web|url=http://shell.windows.com/fileassoc/0409/xml/redir.asp?EXT=xpm|publisher=Microsoft|work=Windows File Association

An X11 libXpm vulnerability was fixed in 2005,{{cite web |access-date=2014-01-01}} and three more in 2023.

FFmpeg version 3.3 or later can decode XPM.

Notes

References

References

1. .xpm [[MIME]] type not [https://www.iana.org/assignments/media-types/media-types.xhtml#image registered] at [[Internet Assigned Numbers Authority. IANA]]
2. (1996-02-01). "XPM Manual: The X PixMap Format". [[Groupe Bull]].
3. Daniel Dardailler. (1996-07-15). "The XPM Story".
4. (1996). "The XPM FAQ". [[X.Org Foundation]].
5. (1996). "XPM File Format Summary". O'Reilly & Associates.
6. Nir Sofer. ".xpm Extension".
7. [[Gravatar]] unofficial, no XPM2
8. Steve Kinzler. (2005). "Picons Archive".
9. (2023-01-17). "X.Org Security Advisory: Issues handling XPM files in libXpm prior to 3.5.15".
10. (2017-04-13). "FFmpeg 3.3 "Hilbert"". [[FFmpeg]].