RAS to CBZ Converter
FileFlip converts RAS to CBZ entirely inside your browser, using ImageMagick and MuPDF compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert a RAS file to CBZ?#
- Drop your RAS file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to CBZ and the conversion starts on its own. FileFlip downloads 24.1 MB of WebAssembly the first time and nothing after that, then runs ImageMagick and MuPDF on your own machine.
- Save the CBZ file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting RAS to CBZ lose quality?#
No. The RAS picture is placed into the CBZ document at its full resolution, so every pixel reaches it intact. What you give up is that it becomes a picture inside a document rather than text.
Is it safe to convert RAS files online?#
Yes, because nothing is uploaded. FileFlip converts RAS files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What RAS to CBZ actually does to the file#
Converting RAS to CBZ runs on ImageMagick and MuPDF, downloads 24.1 MB of WebAssembly the first time and nothing after that, places the picture into the document at full resolution.
| Engine | ImageMagick and MuPDF |
|---|---|
| Conversion path | 2 steps: RAS → PNG → CBZ |
| Downloaded to your browser | 24.1 MB, once, then cached by your browser |
| Quality | Pixels preserved |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
Worth knowing before you start:
- the picture is placed in the document as a picture; no text is recognised out of it
What is a RAS file?#
A RAS file is a Sun Raster bitmap, the raw framebuffer image format Sun Microsystems built into SunOS workstations, and it is byte-for-byte identical to the format most tools also recognise under the .sun extension.
Open a RAS file when it comes from legacy Sun or Solaris workstation software, or from an old dataset captured directly off a SunOS framebuffer.
Convert RAS to PNG or TIFF for anything beyond archival viewing, since almost no current software or web platform accepts Sun Raster natively.
What is a CBZ file?#
A CBZ file is a ZIP archive of page images, usually JPEG or PNG, named so they sort into reading order, with nothing else defining it as a comic beyond that convention.
Use CBZ to distribute a scanned or digital comic as sequential page images that any comic reader opens without conversion.
Convert CBZ to PDF when a comic needs to move into software that expects a page-based document instead of a folder of images.
RAS to CBZ questions people ask#
Is a RAS file the same as a SUN file?
Yes. A RAS file and a SUN file are the same Sun Raster format, identified by the same magic number and header layout, just saved under two different extensions that various tools have used over the years.
What software still opens RAS files?
ImageMagick, GIMP and viewers like IrfanView and XnView still read RAS files, since Sun Raster support has stayed in their format libraries even though the format itself dates to 1980s Sun workstations. Most mainstream photo apps and web browsers do not.
Why is my RAS file so large?
Most RAS files store pixel data uncompressed, since Sun Raster's optional run-length encoding was only ever one of several supported modes rather than the default. Converting to PNG or TIFF typically shrinks the same image considerably.
What is a CBZ file?
A CBZ file is a ZIP archive holding a comic's pages as individual image files, named so they sort into the right reading order. There is no page-layout data or text encoding involved, which is the entire format: a comic reader just opens the ZIP and displays the images in sequence.