Convert JXL to XBM

Why Convert JXL to XBM?

Converting JXL to XBM serves the specialized needs of X11 application developers, embedded system programmers, and Linux desktop customization. XBM's unique property — being valid C source code — means the converted image can be directly compiled into X11 applications without any runtime image loading library. This makes XBM indispensable for creating cursors, toolbar icons, and widget bitmaps in X Window System development.

For embedded systems developers working with monochrome OLED or e-ink displays, XBM provides the simplest possible path from a high-quality JXL source image to a compilable bitmap. The XBM data can be included directly in firmware source code using a C/C++ #include directive, eliminating the need for file system access or image decoder libraries on the target device. This is particularly valuable for microcontrollers with limited flash and RAM.

Linux desktop customization is another practical use case. Window managers like i3, dwm, and Openbox use XBM files for title bar buttons, panel icons, and system tray indicators. Converting modern high-quality JXL icons to XBM allows designers to create these desktop elements using professional tools while producing output that X11 window managers can render natively without additional format support.

The conversion from JXL to XBM involves drastic data reduction — all color, grayscale, HDR, and transparency information is discarded, leaving only 1-bit monochrome pixels. This makes source image selection critical: high-contrast designs with clear outlines, text, and simple geometric shapes produce the best XBM output. The resulting files are text-based and human-readable, which is useful for debugging and manual editing of individual pixels.

Key Benefits of Converting JXL to XBM:

• Compilable Code: XBM is valid C source — #include directly into programs
• X11 Native: Standard format for X Window System icons and cursors
• Embedded Systems: Compile icons into firmware without image libraries
• Human-Readable: Text format editable in any code editor
• Zero Dependencies: No runtime image decoder needed
• Linux Desktop: Native format for window manager customization
• Minimal Footprint: Tiny compiled binary size for icons

Practical Examples

Example 1: X11 Application Icon Development

Scenario: A developer building a custom X11 application needs to create toolbar icons, starting from high-quality JXL design files and producing XBM files that compile directly into the application binary.

Source: toolbar_save.jxl (2 KB, 24×24px, crisp icon design)
Conversion: JXL → XBM (1-bit monochrome)
Result: toolbar_save.xbm (0.4 KB, 24×24px, C source)

X11 development workflow:
1. Design icons in modern tool, export as JXL
2. Convert to XBM (monochrome threshold)
3. #include "toolbar_save.xbm" in C source
4. Use XCreateBitmapFromData() to create X11 Pixmap
✓ Icon compiles directly into application binary
✓ No runtime image loading library needed
✓ Xlib functions read XBM data natively
✓ File is editable C code for manual tweaks

Example 2: Linux Window Manager Customization

Scenario: A Linux user customizes their dwm (dynamic window manager) with custom title bar buttons, converting modern icon designs from JXL to the XBM format that dwm expects.

Source: close_button.jxl (1 KB, 16×16px, clean X design)
Conversion: JXL → XBM (1-bit)
Result: close_button.xbm (0.2 KB, 16×16px)

WM customization:
1. Design button icons in Figma/Inkscape
2. Export as JXL, then convert to XBM
3. Place XBM files in dwm config directory
4. Rebuild dwm with new icons
✓ Native format for tiling window managers
✓ Crisp rendering at small sizes
✓ Matches monochrome aesthetic of minimal WMs
✓ Icons embedded in dwm binary at compile time

Example 3: Embedded OLED Display Icons

Scenario: A hardware developer creates status icons for a 128×64 monochrome OLED display on an Arduino/ESP32 project, starting from JXL design mockups.

Source: wifi_icon.jxl (1 KB, 16×16px, high-contrast design)
Conversion: JXL → XBM (1-bit monochrome)
Result: wifi_icon.xbm (0.2 KB, 16×16px, C array)

Embedded workflow:
1. Design icons in graphic tool with clear outlines
2. Convert JXL to XBM for C-compatible data
3. Include XBM array in Arduino/ESP32 sketch
4. Render on OLED using drawXBitmap() function
✓ XBM format directly usable in Adafruit GFX library
✓ No SD card or file system needed
✓ Icon stored in program flash memory
✓ 128 bytes per 16×16 icon — minimal memory usage

Frequently Asked Questions (FAQ)

Q: What makes XBM unique compared to other image formats?

A: XBM is the only common image format that is valid C source code. An XBM file defines width, height, and pixel data as C preprocessor macros and a static array of unsigned char. This means you can #include "icon.xbm" directly in a C program and use the data without any image parsing or decoding library — a unique property that makes it ideal for compiled applications and embedded systems.

Q: Will my JXL image look the same after converting to XBM?

A: No. XBM is 1-bit monochrome, so all color, grayscale, and transparency information is lost. Pixels are converted to pure black or white using thresholding. The result works well for simple icons, symbols, and high-contrast designs, but photographs and detailed graphics will lose virtually all visual information. Choose source images with clear black-and-white contrast for best results.

Q: Can XBM handle transparency?

A: Not directly. XBM only stores 1-bit data (on/off pixels). However, in X11 programming, transparency is achieved by using a separate XBM file as a clip mask — pixels set to 1 in the mask are visible, pixels set to 0 are transparent. This two-file approach (image + mask) is how X11 cursors and transparent icons work.

Q: What is the relationship between XBM and XPM?

A: XPM (X PixMap) is the color extension of XBM, also stored as C source code but supporting up to 256 colors. XBM is monochrome (1-bit), while XPM adds color through a palette mapping. Both are X11 formats, but XPM is larger and more complex. For monochrome icons and cursors, XBM is preferred; for color icons, XPM or PNG are better choices.

Q: Can I use XBM files in web browsers?

A: Historically, some early browsers supported XBM as an image format, but no modern browser renders XBM images. XBM is strictly a development and system format for X11 applications and embedded systems. For web use, convert JXL to PNG, WebP, or AVIF instead.

Q: How do I use XBM files in Arduino/ESP32 projects?

A: Arduino graphics libraries like Adafruit GFX provide drawXBitmap() functions that render XBM data directly on OLED and LCD displays. Include the XBM file in your sketch, and the bitmap data array is available at compile time. This is the most memory-efficient way to include icons in microcontroller firmware — no SD card or file system needed.

Q: What is the typical file size for XBM icons?

A: XBM files are small but larger than you might expect because they're text, not binary. A 16x16 icon is about 200-300 bytes as XBM text (the hex values plus C syntax). A 32x32 icon is about 600-800 bytes. A 64x64 icon is about 2-3 KB. When compiled into a binary, the actual data is much smaller (32 bytes for 16x16, 128 bytes for 32x32).

Q: Can I edit XBM files in a text editor?

A: Yes, and this is one of XBM's distinctive features. Since XBM files are C source code, you can open them in any text editor and modify individual hex values to change pixels. This is useful for fine-tuning icons without needing an image editor. Some specialized XBM editors like the X11 bitmap utility provide a graphical pixel-editing interface specifically for XBM files.