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What is the Full Meaning of XBM?

Published in Image Formats 3 mins read

XBM stands for X BitMap. It's a plain text binary image format primarily associated with the X Window System.

XBM in Detail

In the context of computer graphics, specifically within the X Window System, XBM serves as a way to store bitmap images. These bitmaps are often used for cursors and icons within the graphical user interface (GUI) of X. Because it's a plain text format, XBM files are human-readable (though not easily interpretable visually). They essentially consist of C code that defines the pixel data for the image.

Key Characteristics of XBM:

  • Text-Based: XBM files are stored as plain text, making them easily editable with text editors.
  • Binary Image Format: While text-based, the data represents binary pixel values (on or off).
  • Limited Color Support: XBM only supports two colors: black and white (or foreground and background). It cannot represent grayscale or color images directly.
  • Uses C Syntax: The format relies on C language syntax to define the image data, making it somewhat unique among image formats.
  • Superseded by XPM: The XBM format has largely been replaced by XPM (X PixMap), which offers support for multiple colors. XPM first appeared for X11 in 1989.

Example of an XBM file (hypothetical):

#define my_image_width 16
#define my_image_height 16
static unsigned char my_image_bits[] = {
   0x13, 0x00, 0x15, 0x00, 0x93, 0x00, 0x85, 0x00, 0x8d, 0x00, 0xa5, 0x00,
   0xa5, 0x00, 0x8d, 0x00, 0x85, 0x00, 0x93, 0x00, 0x15, 0x00, 0x13, 0x00};

In this simplified example:

  • my_image_width and my_image_height define the dimensions of the image.
  • my_image_bits is an array of unsigned characters that hold the actual pixel data. Each byte represents a row of pixels. A "1" bit signifies a pixel of one color (e.g., black), and a "0" bit signifies the other color (e.g., white).

Why XBM is Less Common Today:

The limitations of XBM, particularly its monochrome nature, led to its decline in favor of more versatile image formats like XPM, PNG, and others. While you might still encounter XBM files in older systems or specific niche applications, they are far less prevalent than they once were.

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