X PixMap

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 <Values> <Colors> <Pixels> <Optional Extensions> 

• 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 

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.

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.

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 

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]

• Netpbm – Toolkit for manipulation of images
• CLUT – In computer graphics, a finite set of available colorsPages displaying short descriptions of redirect targets
• X BitMap – File format

• X Window System (X11) and X11 color names
• PBM (mono), PGM (grayscale), PPM (color), PNM (any)
• X BitMap

• libXpm - X Pixmap (XPM) image file format library