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]
XPM[edit]
The XPM format is an array of strings composed of six different sections as follows:
static char* <variable_name>[] = {
<Values>
<Colors>
<Pixels>
<Extensions>
};
This is a black-and-white image in the first (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
The values section contains the width, height, number of colors, and number of characters per pixel.
XPM2[edit]
XPM2 simplifies the format by removing all C code. An example:
! XPM2 48 4 2 1 a c #FFFFFF b c #000000 abaabaababaaabaabababaabaabaababaabaaababaabaaab abaabaababaaabaabababaabaabaababaabaaababaabaaab abaabaababaaabaabababaabaabaababaabaaababaabaaab abaabaababaaabaabababaabaabaababaabaaababaabaaab
This is an XPM2 file with width 48, height 4, 2 colors, and 1 character per pixel. 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.
XPM3[edit]
The other styles XPM1 and XPM3 are designed to be used as is in C source code, example:
/* XPM */
static char * XFACE[] = {
/* <Values> */
/* <width/columns> <height/rows> <colors> <chars per pixel>*/
"48 4 2 1",
/* <Colors> */
"a c #ffffff",
"b c #000000",
/* <Pixels> */
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab",
"abaabaababaaabaabababaabaabaababaabaaababaabaaab"
};
The latter format is XPM3, the common format used for the X Window System since about 1991. The c means "color", it's possible to add m for "monochrome" output, g for "grayscale", and s for "symbolic", explaining what a defined color is supposed to do.
In addition to the X11 color names the name 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.
If the width, height, colors, and characters per pixel line contains six instead of four numbers, the additional values indicate the coordinates of a "hotspot", 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]
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[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] FFmpeg version 3.3 or later can decode XPM.[11]
See also[edit]
- X Window System (X11) and X11 color names
- PBM (mono), PGM (grayscale), PPM (color), PNM (any)
References[edit]
- ^ .xpm MIME type not registered at IANA
- ^ a b Le Hors, Arnaud (1996-02-01). XPM Manual: The X PixMap Format (PDF). Groupe Bull. pp. 7–8. Retrieved 2014-01-01.
- ^ 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.
- ^ "The XPM FAQ". X.Org Foundation. 1996. Retrieved 2016-03-12.
- ^ "XPM File Format Summary". Encyclopedia of Graphics File Formats, 2nd Edition. ISBN 1-56592-161-5. Retrieved 2014-01-01.
- ^ Nir Sofer. ".xpm Extension". Retrieved 2014-01-12.
- ^ "File Type: X Windows Pixmap". Windows File Association. Microsoft. 2013. Retrieved 2014-01-12.
- ^ Gravatar unofficial, no XPM2
- ^ Steve Kinzler (2005). "Picons Archive". Retrieved 2014-01-06.
picons are in either monochrome XBM format or color XPM and GIF formats
- ^ "libXpm library contains multiple integer overflow vulnerabilities". US-CERT. 2005-10-06. VU#537878. Retrieved 2014-01-01.
- ^ "FFmpeg 3.3 "Hilbert"". FFmpeg. 2017-04-13. Retrieved 2017-10-28.
XPM decoder