FITS to XPM Converter
Processing entirely on your device — large files may take a moment.
Flexible Image Transport System and X11 Pixmap exist for different jobs: FITS (Flexible Image Transport System) is the data format of professional astronomy — every image carries a human-readable header with telescope, exposure and world coordinates alongside the raw pixel data. Convert PNG or SVG output to XPM to feed icon themes and legacy toolkits.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How FITS compares to XPM
| FITS | XPM | |
|---|---|---|
| Compression | None (optionally Rice/GZIP) | None (ASCII text) |
| Transparency | Not supported | Single transparent color |
| Animation | Not supported | Not supported |
| Metadata | Rich text header (WCS) | Not supported |
| Best for | Telescope frames, science data | Linux icons, X11 themes |
How to convert FITS to XPM
- 1
Select your files
Drag & drop your FITS files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to XPM". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted XPM file individually, or grab everything at once as a ZIP archive.
About the FITS format
FITS (Flexible Image Transport System) has carried professional astronomy data since 1981: every file opens with a plain-text header that records telescope, instrument, exposure, filters and world coordinates, followed by raw pixel arrays — often 16-bit or float, sometimes data cubes.
Values can be negative or far above display range, so FITS never looks right in a photo viewer. Converting to PNG applies a simple scaling pass that reveals the nebula or galaxy in the numbers — good for previews, while science pipelines keep the original.
+Strengths
- ✓Self-documenting science headers
- ✓High bit depth (16/32-bit, float)
- ✓The standard of every observatory
!Limitations
- −Not display-ready
- −Files are large and uncompressed
About the XPM format
XPM (X11 Pixmap) is an image format that is literally C source code: pixels are listed as character-to-color mappings inside an ASCII array. Compilers, text editors and version control all treat it as plain text, which is why Linux desktop icons and legacy X11 application assets have used it for decades.
XPM is limited to 256 colors per image and stores no alpha beyond a designated transparent character, so it is a niche target: mainly icon themes, window-manager decorations and retro programming projects.
+Strengths
- ✓Plain text — diffs and greps
- ✓Compiles straight into C programs
- ✓Tiny for small flat icons
!Limitations
- −256 colors maximum
- −Poor alpha (one transparent color)
Why convert FITS to XPM?
There is a concrete reason this conversion exists: Not display-ready XPM sidesteps that — Plain text — diffs and greps If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this FITS to XPM converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Will I lose quality converting FITS to XPM?
No — XPM is a lossless format, so every pixel of the converted image matches your original FITS file. You can also adjust the quality/size balance before converting when the target format supports compression.
Will transparent areas survive the conversion to XPM?
Transparency is kept whenever XPM actually supports an alpha channel. If the target format has none (like JPG), transparent areas are flattened onto a white background — that is a property of the format, not of this tool.
Can I convert several FITS files at once?
Yes — drop as many files as you like into the tool and they are converted in one batch. When more than one file comes out, everything is bundled into a ZIP for a single download.