X PixMap (original) (raw)

From Wikipedia, the free encyclopedia

Image file format

X PixMap

Some text editors, for example gvim, can display xpm images in graphical form
Filename extension .xpm
Internet media type image/x-xpixmap[1]
Developed by BULL Research
Type of format Image file formats
Extended from XBM
Open format? yes

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.[2][3]

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.[2]

The first (1989) XPM format is relatively similar to the XBM format.[a] 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 (1990) simplifies the format by removing all C code.[b][c] The structure is simplified to

! XPM2

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

In addition to hexcodes, the colors can be any of the X11 color names. In addition, None indicates transparency.[4][5]

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

[edit]

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 = 1000000000 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.

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

[edit]

Blarg file opened in program window

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 };

Blarg.xpm (XPM2) rendered by XnView

XPM2 version:

! XPM2 16 7 2 1

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

[edit]

ACDSee, Amaya, CorelDRAW, GIMP, ImageMagick, IrfanView (formats plugin), PaintShop Pro, PMView, Photoshop (plugins), and XnView among others support XPM.[6][7] Gravatar and picons also support XPM.[8][9]

An X11 libXpm vulnerability was fixed in 2005,[10] and three more in 2023.[11]

FFmpeg version 3.3 or later can decode XPM.[12]

  1. ^ For a description of this format in lieu of the manual (not found on the Internet), use xpm-contrib (formerly part of libXpm proper) converter (xpm2ppm, xpm1to3, xpm1to2c) source code.

  2. ^ It is also acceptable to use programming language syntaxes for string arrays, but only the C syntax is attested. The "XPM2 C" syntax eventually became the only format in XPM version 3.

  3. ^ For references on this syntax, see https://gitlab.freedesktop.org/xorg/lib/libxpm/-/blob/master/NEWS.old and the "history" section of libXpm 3.4 manual.

  4. ^ .xpm MIME type not registered at IANA

  5. ^ a b Le Hors, Arnaud (1996-02-01). XPM Manual: The X PixMap Format (PDF). Groupe Bull. pp. 7–8. Retrieved 2014-01-01.

  6. ^ Daniel Dardailler (1996-07-15). "The XPM Story". Colas Nahaboo and Arnaud Le Hors. Archived from the original on 1997-06-07. Retrieved 2014-01-01.

  7. ^ "The XPM FAQ". X.Org Foundation. 1996. Retrieved 2016-03-12.

  8. ^ Murray, James D.; Vanryper, William (1996). XPM File Format Summary. O'Reilly & Associates. ISBN 1-56592-161-5. Retrieved 2014-01-01.

  9. ^ Nir Sofer. ".xpm Extension". Retrieved 2014-01-12.

  10. ^ "File Type: X Windows Pixmap". Windows File Association. Microsoft. 2013. Retrieved 2014-01-12.

  11. ^ Gravatar unofficial, no XPM2

  12. ^ Steve Kinzler (2005). "Picons Archive". Retrieved 2014-01-06. picons are in either monochrome XBM format or color XPM and GIF formats

  13. ^ "libXpm library contains multiple integer overflow vulnerabilities". US-CERT. 2005-10-06. VU#537878. Retrieved 2014-01-01.

  14. ^ "X.Org Security Advisory: Issues handling XPM files in libXpm prior to 3.5.15". 2023-01-17.

  15. ^ "FFmpeg 3.3 "Hilbert"". FFmpeg. 2017-04-13. Retrieved 2017-10-28. XPM decoder