{"id":"image-x-cmu-raster","mimeType":"image/x-cmu-raster","name":"CMU Window Manager Raster","shortName":"CMU-Raster","category":"Legacy \u0026 Raster Graphics","extensions":[".ras"],"description":"The image/x-cmu-raster MIME type represents the CMU Raster format, an early digital image format created at Carnegie Mellon University (CMU) in the 1980s. It served as the native bitmap graphic format for the CMU Window Manager and the Andrew User Interface System (AUIS)—a pioneering, joint academic computing project between CMU and IBM. Designed for the UNIX workstations of the era, the format is a highly simplified, uncompressed raster image, typically storing 1-bit monochrome pixel data. It is now completely obsolete and encountered almost exclusively in historical UNIX archives.","seo":{"title":"image/x-cmu-raster MIME Type | Developer Reference for CMU Raster","description":"Complete reference for the image/x-cmu-raster MIME type: Carnegie Mellon University (CMU) Raster, Andrew Project history, .ras file conflicts, and Netpbm.","faqs":[{"question":"What is a CMU Raster file?","answer":"A CMU Raster file is a legacy, uncompressed image format from the 1980s. It was used primarily by the Carnegie Mellon University Window Manager and the Andrew Toolkit to render basic graphics on early UNIX workstations."},{"question":"Why is my .ras file opening as a Sun Raster image instead?","answer":"The '.ras' file extension is heavily overloaded in legacy computing. It is most famously associated with Sun Microsystems' Sun Raster format. Because the CMU Raster format is practically extinct, modern software and operating systems will almost always assume a '.ras' file belongs to the Sun ecosystem."},{"question":"How do I view or convert a CMU Raster image today?","answer":"Modern web browsers and consumer image viewers cannot open CMU Raster files. You must use legacy command-line image processing suites like Netpbm (specifically the 'cmuwmtopbm' command) or ImageMagick to convert them into modern formats like PNG or JPEG."}]},"index":{"compression":["Uncompressed"],"browserSupport":{"score":1,"label":"None"},"commonUses":["Historical UNIX / Andrew Project Archival","Legacy Academic Computing Research"]},"technical":{"magicBytes":{"hex":"F1 00 40 BB","ascii":"\\xF1\\x00\\x40\\xBB"},"container":"CMU Window Manager Bitmap","compressionAlgorithm":["None"],"colorDepth":["1-bit (Monochrome)","8-bit (Indexed/Grayscale)"],"transparency":false,"animation":false,"metadata":{"exif":false,"xmp":false,"iccProfile":false},"alphaChannel":false,"progressiveLoading":false,"hdrSupport":false},"history":{"developer":"Carnegie Mellon University (CMU)","released":"1980s","specification":"Andrew Toolkit / AUIS Source Code Documentation"},"browserSupport":{"chrome":false,"chromeVersion":"None","firefox":false,"firefoxVersion":"None","safari":false,"safariVersion":"None","edge":false,"edgeVersion":"None","internetExplorer":false},"softwareSupport":[{"name":"Netpbm (cmuwmtopbm / pbmtocmuwm)","logo":""},{"name":"ImageMagick","logo":"image-magic.webp"}],"conversion":{"convertTo":["png","pbm","jpeg"],"convertFrom":["pbm"]},"developer":{"httpHeaders":[{"header":"Content-Type","value":"image/x-cmu-raster"}],"htmlAccept":"None","fileDetection":["Check the first 4 bytes for the CMU Window Manager magic number (Hex: F1 00 40 BB).","Because the .ras extension is widely shared with the Sun Raster format (Magic Bytes: 59 A6 6A 95), checking the file header is absolutely mandatory to differentiate between the two."]},"prosCons":{"pros":["Incredibly simple, uncompressed binary structure that was easy for early, memory-constrained UNIX workstations to parse and render"],"cons":["Completely obsolete and unsupported outside of niche historical command-line tools like Netpbm","The shared '.ras' file extension causes frequent file misidentification and system conflicts","Lacks all modern imaging features, including metadata, compression, and alpha channel transparency"]},"specifications":{"url":"http://netpbm.sourceforge.net/doc/cmuwmtopbm.html","rfc":"","mimeAliases":["image/cmu-raster"]},"developerSnippets":{"python":"import magic\n# Libmagic contains definitions for the CMU Window Manager bitmap magic bytes.\nprint(magic.from_file('archive.ras', mime=True)) # Outputs 'image/x-cmu-raster'","nodejs":"const fs = require('fs');\n// Manually detecting the CMU Raster magic bytes to avoid Sun Raster (.ras) conflicts\nconst buffer = Buffer.alloc(4);\nconst fd = fs.openSync('archive.ras', 'r');\nfs.readSync(fd, buffer, 0, 4, 0);\nfs.closeSync(fd);\nconst isCmuRaster = buffer[0] === 0xF1 \u0026\u0026 buffer[1] === 0x00 \u0026\u0026 buffer[2] === 0x40 \u0026\u0026 buffer[3] === 0xBB;\nconsole.log('Is CMU Raster:', isCmuRaster);","go":"import (\n    \"bytes\"\n    \"net/http\"\n)\n// Native Go HTTP detection will not recognize CMU Raster.\n// You must explicitly check for the 4-byte magic signature.\n// isCmuRaster := bytes.HasPrefix(buf, []byte{0xF1, 0x00, 0x40, 0xBB})","php":"$mime = mime_content_type('archive.ras');\necho $mime; // Standard PHP setups will likely return 'application/octet-stream' or incorrectly map the extension to 'image/x-sun-raster'"},"relatedFormats":["x-sun-raster","pbm","bmp"]}