Decoding raw digital photos in Linux

Not affiliated with Canon, Nikon, Kodak, or any other company named herein.

Welcome! If you are wondering how to connect your digital camera and download images to a Linux PC, go to the gPhoto homepage. My software is for processing those images after downloading them.

If you're downloading JPEG files, you don't need my software at all. The image has already been processed inside the camera. Almost all digital cameras made since 1997 produce JPEG images, so why would you want to do it any other way?

Well, despite the convenience and ubiquity of JPEG, there are some disadvantages. JPEG is a lossy format -- to fit a big image into a small file, a lot of information is thrown away. That's why midrange and high-end digital cameras offer an alternative: Raw, unprocessed CCD data files, for which the camera manufacturer provides special decoding software.

Of course this software is for Windows and Macintosh only, with no source code. So it's useless to users of other operating systems, programmers hoping to design a better interpolation algorithm, and historians not yet born in an era when the only Windows machines will be in museums.

So here is my mission: Write and maintain an ANSI C program that decodes any raw image from any digital camera on any computer running any operating system.

That program is called dcraw.c, and it's become a standard tool within and without the Open Source world. It's small (about 7000 lines), portable (standard C libraries only), free (both "gratis" and "libre"), and when used skillfully, produces better quality output than the tools provided by the camera vendor.

Here's my resume. I do freelance consulting related to dcraw, and I'm also available for full-time work in BIOS engineering or UNIX system administration.

I can be reached by sending e-mail to cybercom dot net with the username "dcoffin".

My Code

There are no restrictions on this code, although I would like to receive credit for it. Donations are welcome, especially if you're using my code commercially.

Note to Linux distributors: The only executable files that should be installed by a dcraw package are "dcraw", "clean_crw", and maybe "fuji_green", "fujiturn", and "fujiturn16". My shell scripts are dangerous and should only be installed in a "doc" directory without execute permission.

dcraw.c -- decodes raw photos, extracts thumbnails, and displays metadata
Supports 226 cameras at last count. Compile with "gcc -o dcraw -O4 dcraw.c -lm -ljpeg -llcms" or "gcc -o dcraw -O4 dcraw.c -lm -DNO_JPEG -DNO_LCMS". Run with no arguments to see a usage message. Don't complain that 16-bit output is too dark -- read the FAQ!
rawphoto.c -- basic plugin for GIMP 1.2 & 2.0
After installing "dcraw", do "gimptool --install rawphoto.c". My plugin provides a simple dialog box for loading raw files into the Gimp. Udi Fuchs and Joseph Heled have written much nicer plugins, with live preview, histograms, and color curves.
.badpixels -- my camera's "hot pixels"
This file tells dcraw which pixels have died and when, so that it can interpolate around them.
dcraw.1 -- UNIX manpage for dcraw
Contains details and helpful hints not found elsewhere.
dcraw.c,v -- complete unabridged RCS file
This file contains the entire history of dcraw.c since its conception on February 23, 1997. If you don't have the RCS toolkit, download it here.
parse.c -- read image data structures
This program displays CIFF and TIFF data structures in a very cryptic format.
clean_crw.c -- clean Canon CRW files
Recovered or undeleted CRW files often have junk appended to them that makes them unreadable. This program safely cleans CRW files.
fujiturn.c -- rotate Fuji Super CCD images
An alternative to dcraw's built-in Fuji rotation.
fuji_green.c -- convert Fuji green pixels to PGM
A side benefit of the Fuji Super CCD design is that its green pixels make nice black-and-white images.

For hackers only:

decompress.c is a simple reference decompressor for CRW files.
sony_clear.c decrypts SRF files from the Sony DSC-F828.

Other Raw Photo Decoders

Dcraw has made it far easier for developers to support a wide range of digital cameras in their applications. They can call dcraw from a graphical interface, paste pieces of dcraw.c into their code, or just use dcraw.c as the documentation that camera makers refuse to provide:

Frequently Asked Questions

I don't have a C compiler. Could you send me an executable?

No, but Francisco Montilla provides Mac OS and Windows executables on his website. And Benjamin Lebsanft has volunteered to maintain Windows executables optimized for specific CPUs.

If you're familiar with the DOS command line but don't know C, you can install this free C compiler for Windows and compile dcraw.c quite easily.

How can I read the EXIF data (shutter speed, aperture, etc.)?

Phil Harvey's ExifTool provides a unified Perl-based EXIF reader (and editor!) for all cameras and file formats. "dcraw -i -v" is much faster, but provides less information.

How can I read NEF files from Nikon scanners?

Dcraw only supports cameras. Try this simple program for scanners.

How can I read Nikon Dust Off images (NDF files)?

Use this program.

Do you have any specifications describing raw photo formats?

Yes, but they tend to omit important details, like how to decompress the raw image or decrypt private metadata. See the TIFF spec, the TIFF/EP spec, the Adobe DNG spec, the CIFF (CRW) spec, and the X3F spec.

I'm designing a digital camera. How do I convert its raw photos into something that dcraw and Adobe Photoshop can open?

Download LibTIFF v3.8.0 and apply this patch. Then use this C program as a template for converting your photos to valid Adobe DNG files.

I shot a raw photo with no light. Why does it appear all noisy, when it should be solid black?

No matter how dark an image is, dcraw's auto-exposure stretches it so that one percent of its pixels appear white. The "-b" option adjusts this behavior, while "-4" (16-bit output) avoids it entirely.

I bracket plus/minus two stops, but all five shots look almost the same in dcraw. Why?

See the previous question.

Why is 16-bit output dark / unreadable?

If you want pretty pictures straight out of dcraw, stay with 8-bit output. 16-bit linear output is the best raw material for professional image editors such as Photoshop and CinePaint, but it's no good for most image viewers.

What does the "-f" (four color RGB) option do?

If you see patterns like this or this in your output images, first try "dcraw -a". If these patterns persist, use "dcraw -f" to get rid of them.

Could you please add an option for TIFF / FITS / PNG / BMP / JPEG output?

In versions 8.25 and later, "dcraw -T" writes TIFF output with metadata. To write other formats:
dcraw -c crw_0001.crw | pnmtofits > crw_0001.fits dcraw -c crw_0001.crw | pnmtopng > crw_0001.png dcraw -c crw_0001.crw | ppmtobmp > crw_0001.bmp dcraw -c crw_0001.crw | cjpeg > crw_0001.jpeg
I used the Netpbm toolkit in these examples. ImageMagick also does command-line format conversions. Both are free.

Why don't you implement dcraw as a library?

I have decided that dcraw shall be a command-line program written in C, and that any further abstraction layers must be added around this core, not inside it.
Library code is ugly because it cannot use global variables. Libraries are more difficult to modify, build, install, and test than standalone programs, and so are inappropriate for file formats that change every day.
There's a simpler way to make dcraw modular and thread-safe: Run it as a separate process. Eric Raymond explains this technique here.

Why are there false colors along edges within the image?

Because of interpolation. This is a hard problem, easily defined:

Take a three-color RGB image. At each pixel, set two color values to zero.
Reconstruct the original three-color image as best you can from the remaining one color per pixel.
Dcraw currently gives a choice of three methods: Bilinear, Variable Number of Gradients (VNG), and Adaptive Homogeneity-Directed (AHD).
The Foveon X3 Capture chip requires a different kind of interpolation. Unlike CCD arrays, it captures three colors at every pixel location. But the colors are not well separated, so the raw data looks very gray. Much processing is needed to enhance color while suppressing noise.

How do I get my camera to take raw photos?

For some Nikon Coolpix cameras, you need to enable a special "DIAG RAW" mode.
For Casio cameras, see Maurice Delaney's website or read this discussion on dpreview.
For the Minolta DiMAGE G400, G500, G530, or G600, go here (in Russian) or here (in English).
For the Minolta DiMAGE Z2 and Nikon Coolpix 2100/3100/3700, go here.
For SMaL cameras, see the camerahacking Forum.
For other cameras, refer to the User's Manual.

Does dcraw work with my camera?

Most likely, yes. The cameras listed below are supported. If your camera is not on the list, try dcraw anyway. If it doesn't work, post a raw image to a website and e-mail me the URL. If you don't have a website, use Dropload or YouSendIt.
Ideally, your sample image should show a standard white card or color chart in direct sunlight, with other colors in the background.

Adobe Digital Negative (DNG)
AVT F-145C
AVT F-201C
AVT F-510C
AVT F-810C
Canon PowerShot 600
Canon PowerShot A5
Canon PowerShot A5 Zoom
Canon PowerShot A50
Canon PowerShot Pro70
Canon PowerShot Pro90 IS
Canon PowerShot G1
Canon PowerShot G2
Canon PowerShot G3
Canon PowerShot G5
Canon PowerShot G6
Canon PowerShot S30
Canon PowerShot S40
Canon PowerShot S45
Canon PowerShot S50
Canon PowerShot S60
Canon PowerShot S70
Canon PowerShot Pro1
Canon EOS D30
Canon EOS D60
Canon EOS 5D
Canon EOS 10D
Canon EOS 20D
Canon EOS 30D
Canon EOS 300D / Digital Rebel / Kiss Digital
Canon EOS 350D / Digital Rebel XT / Kiss Digital N
Canon EOS D2000C
Canon EOS-1D
Canon EOS-1DS
Canon EOS-1D Mark II
Canon EOS-1D Mark II N
Canon EOS-1Ds Mark II
Casio QV-2000UX
Casio QV-3000EX
Casio QV-3500EX
Casio QV-4000
Casio QV-5700
Casio QV-R51
Casio QV-R61
Casio EX-S100
Casio EX-Z50
Casio EX-Z55
Casio Exlim Pro 505
Casio Exlim Pro 600
Casio Exlim Pro 700
Contax N Digital
Creative PC-CAM 600
Epson R-D1
Foculus 531C
Fuji FinePix E550
Fuji FinePix E900
Fuji FinePix F700
Fuji FinePix F710
Fuji FinePix F800
Fuji FinePix F810
Fuji FinePix S2Pro
Fuji FinePix S3Pro
Fuji FinePix S20Pro
Fuji FinePix S5000
Fuji FinePix S5100/S5500
Fuji FinePix S5200/S5600
Fuji FinePix S7000
Fuji FinePix S9000/S9500
Imacon Ixpress 16-megapixel
Imacon Ixpress 22-megapixel
Imacon Ixpress 39-megapixel
ISG 2020x1520
Kodak DC20 (see Oliver Hartman's page)
Kodak DC25 (see Jun-ichiro Itoh's page)
Kodak DC40
Kodak DC50
Kodak DC120 (also try kdc2tiff)
Kodak DCS315C
Kodak DCS330C
Kodak DCS420
Kodak DCS460
Kodak DCS460A
Kodak DCS520C
Kodak DCS560C
Kodak DCS620C
Kodak DCS620X
Kodak DCS660C
Kodak DCS660M
Kodak DCS720X
Kodak DCS760C
Kodak DCS760M
Kodak EOSDCS1
Kodak EOSDCS3B
Kodak NC2000F
Kodak ProBack
Kodak PB645C
Kodak PB645H
Kodak PB645M
Kodak DCS Pro 14n
Kodak DCS Pro 14nx
Kodak DCS Pro SLR/c
Kodak DCS Pro SLR/n
Kodak P850
Kodak P880
Kodak KAI-0340
Konica KD-400Z
Konica KD-510Z
Leaf Aptus 17
Leaf Aptus 22
Leaf Aptus 65
Leaf Aptus 75
Leaf Cantare
Leaf CatchLight
Leaf CMost
Leaf DCB2
Leaf Valeo 6
Leaf Valeo 11
Leaf Valeo 17
Leaf Valeo 22
Leaf Volare
Leica Digilux 2
Leica D-Lux 2
Logitech Fotoman Pixtura
Micron 2010
Minolta RD175
Minolta DiMAGE 5
Minolta DiMAGE 7
Minolta DiMAGE 7i
Minolta DiMAGE 7Hi
Minolta DiMAGE A1
Minolta DiMAGE A2
Minolta DiMAGE A200
Minolta DiMAGE G400
Minolta DiMAGE G500
Minolta DiMAGE G530
Minolta DiMAGE G600
Minolta DiMAGE Z2
Minolta Alpha/Dynax/Maxxum 5D
Minolta Alpha/Dynax/Maxxum 7D
Nikon D1
Nikon D1H
Nikon D1X
Nikon D100
Nikon D2H
Nikon D2Hs
Nikon D2X
Nikon D200
Nikon D50
Nikon D70
Nikon D70s
Nikon E700 ("DIAG RAW" hack)
Nikon E800 ("DIAG RAW" hack)
Nikon E880 ("DIAG RAW" hack)
Nikon E900 ("DIAG RAW" hack)
Nikon E950 ("DIAG RAW" hack)
Nikon E990 ("DIAG RAW" hack)
Nikon E995 ("DIAG RAW" hack)
Nikon E2100 ("DIAG RAW" hack)
Nikon E2500 ("DIAG RAW" hack)
Nikon E3700 ("DIAG RAW" hack)
Nikon E4300 ("DIAG RAW" hack)
Nikon E4500 ("DIAG RAW" hack)
Nikon E5000
Nikon E5400
Nikon E5700
Nikon E8400
Nikon E8700
Nikon E8800
Olympus C3030Z
Olympus C5050Z
Olympus C5060WZ
Olympus C7070WZ
Olympus C70Z,C7000Z
Olympus C740UZ
Olympus C770UZ
Olympus C8080WZ
Olympus E-1
Olympus E-10
Olympus E-20
Olympus E-300
Olympus E-330
Olympus E-500
Olympus SP310
Olympus SP320
Olympus SP350
Olympus SP500UZ
Panasonic DMC-FZ30
Panasonic DMC-LC1
Panasonic DMC-LX1
Pentax *ist D
Pentax *ist DL
Pentax *ist DL2
Pentax *ist DS
Pentax *ist DS2
Pentax K100D
Pentax Optio S
Pentax Optio S4
Pentax Optio 33WR
Phase One LightPhase
Phase One H 10
Phase One H 20
Phase One H 25
Phase One P 20
Phase One P 25
Phase One P 30
Phase One P 45
Pixelink A782
Polaroid x530
Rollei d530flex
RoverShot 3320af
Samsung GX-1S
Sarnoff 4096x5440
Sigma SD9
Sigma SD10
Sinar 3072x2048
Sinar 4080x4080
Sinar 4080x5440
Sinar STI format
SMaL Ultra-Pocket 3
SMaL Ultra-Pocket 4
SMaL Ultra-Pocket 5
Sony DSC-F828
Sony DSC-R1
Sony DSC-V3
Sony DSLR-A100
Sony XCD-SX910CR
STV680 VGA