dcraw
| dcraw | |
|---|---|
| Basic data
|
|
| developer | Dave Coffin |
| Publishing year | February 23, 1997 |
| Current version |
9.28 ( June 1, 2018 ) |
| operating system | Unix ( GNU / Linux , macOS , BSD , AIX ), OS / 2 , Windows etc. a. |
| programming language | C. |
| category | Graphics software |
| License | public domain , partly GPLv 2 |
| German speaking | Yes |
| Homepage of dcraw | |
dcraw (after the initials of the programmer Dave Coffin) is free software for converting raw data images from digital cameras. The program can process the mostly proprietary, insufficiently or not at all documented image formats of almost all digital cameras on the market.
Emergence
Starting point and catalyst was the emergence of high-quality, mostly SLR - digital cameras , in addition to saving the captured images as JFIF files, the direct storage in the raw data format allowed. The advantages of working with images in raw data formats are the advanced editing and correction options (e.g. white balance ) and the greater dynamic range of the lossless 14 or 12-bit data compared to the lossy 8-bit JPEG images. The decisive disadvantage, however, is that all camera manufacturers use different, mutually incompatible and also different formats for their raw data images within a production series. In some cases, the information is also encrypted or concealed in order to make it more difficult for third parties to access it.
For all these cameras, the manufacturers offer programs (which may also be purchased) that can read and convert their raw data formats. However, these have two shortcomings: On the one hand, they consist entirely of proprietary software , i.e. non-free applications that can only be used on an operating system or hardware platform that is compatible with the manufacturer. Associated with this is the second problem: If a camera is taken off the market because a successor appears, the manufacturer abandons the series or disappears completely , support for these programs ends either immediately or after a certain period of time. There is no guarantee or obligation that the function of the raw data conversion software required for this camera will be incorporated into that for another camera or a successor model. If the associated operating system / hardware combination is now out of use, there is no longer any possibility of using the raw data images from the camera.
In order to remedy this shortcoming, dcraw was created : A free , easy-to-use, portable program that supports as many cameras as possible and, following the Unix philosophy , fulfills exactly one task. dcraw is a command line program to which the names of the raw data images to be processed and the associated settings are transferred as command line parameters. dcraw outputs the converted images either in TIFF or PPM format on the standard output , so the result can easily be further processed and dcraw can be easily integrated into shell scripts.
use
Although possible and useful in some application scenarios, dcraw is usually not used immediately. This is also intended - the program acts as a backend that does the raw data conversion; all further image processing steps are then carried out by the actual application program. In addition to programs specializing in raw data conversion, such as B. UFRaw or Rawstudio , which do not call dcraw but have integrated its source code, also include other image processing programs as well as image databases and special applications, e.g. B. for evaluating the images from surveillance cameras or astronomical recordings.
There is also a special version dcrawps that is able to process the PSR (pixel shift resolution) images of the Pentax K-3 II and the Pentax K-1 . Four images, each shifted by one pixel, are stored in the raw data files. The shift takes place in such a way that each pixel is recorded with the associated four Bayer filters (RGBG), these are then superimposed in the raw development and thus increase the color resolution of the sensor.
Examples
In addition to the conversion, dcraw can do a number of other raw data processing.
General Exif information such as B. used camera, aperture, focal length and exposure time can be determined as follows:
dcraw -v -i IMG_1234.RAW
Most raw data formats contain an embedded JPEG preview image. This can be IMG_1234.thumb.jpgextracted into the file :
dcraw -e IMG_1234.RAW
The actual conversion into the binary coded 8-bit PPM file takes place without additional parameters IMG_1234.ppm:
dcraw IMG_1234.RAW
One for further processing z. A PNG file suitable for example with GIMP or CinePaint can easily be generated through a pipe using NetPBM :
dcraw -4 -c IMG_1234.RAW | pnmtopng > IMG_1234.png
TIFF files can be created by dcraw directly:
dcraw -T -6 IMG_1234.RAW
Supported cameras
According to the website (as of June 2018), the current version supports the raw data formats of 598 cameras, the majority of all digital cameras ever produced in significant numbers, including all models from the two market rivals Nikon and Canon . In addition, there is generic support for Adobe's digital negative format and all cameras that produce it.
Software that uses the code from dcraw
Web links
Individual evidence
- ↑ www.cybercom.net .
- ↑ www.cybercom.net . (accessed on July 7, 2018).
- ↑ Digital Photography Review: Dave Coffin interviewed (English)
- ↑ Github dcrawps
- ↑ Dave Coffin: Decoding raw digital photos in Linux (English)