CRW(1) BSD General Commands Manual CRW(1)NAMEcrw — Process RAW Canon PowerShot photos
SYNOPSIScrw [-c] [-s num] [-g num] [-b num] [-r num] [-l num] [-B num] [-L num]
[-bw] [-inside] [-2] [-3] [-4] files
DESCRIPTION
The crw utility processes RAW output files (.crw) from Canon Powershot
digital cameras, typically converting them into .ppm files. By default,
crw uses a gamma of 0.8 (the lower the brighter) and a low-light compen‐
sation value of 16 (higher values == more compensation, 0 disables).
Different CCDs also have different scaling factors for their filter com‐
ponents. This program will automatically scale filter components for the
CCD (though our values may not be entirely correct. The red scaling for
the CanonG2 was wrong in the original program, before I fixed it). The
program renormalizes the data to a scaling of 1.0/1.0/1.0 before applying
adjustments specified on the command line.
The resolution of the output file will typically be somewhat smaller then
the resolution of the raw .crw file due to edge effects during process‐
ing. RAW files contain one color per pixel in a matrix which must be
processed to synthesize the missing colors and generate photo output.
You can see the raw CCD matrix (with thermal noise and filter compensa‐
tion by default) by running the program with the option: -s -1.
The following options are available:
-c Generate the converted image file on the standard output. If not
specified the image file is generated using the input filename with
an appropriately replaced extension.
-s num
Specify the smoothness factor. Currently only -1 and 0 may be
specified. -1 will cause crw to transfer the raw CCD pixels to the
standard output in the requested image file format. The default is
0. You can produce a certain degree of smoothing by changing the
low-light adjustment, which is the
-L option.
-g num
Set the gamma. The default is 0.8. A value of 1.0 will produce
output with no gamma correction. Lower values will produce
brighter output images. Gamma is a non-uniform exponential adjust‐
ment of the image brightness that tends to bring out darker areas
of an image. This only works for .ppm image output.
-b num
Set the brightness. Brightness is a more uniform, linear brighten‐
ing of the image. The default is 1.0. A higher value will produce
a brighter image. We recommend using the gamma adjustment whenever
possible instead of the brightness adjustment.
-r num
Set the red scaling. The default is 1.0. The red and blue scaling
factors are typically used to compensate for artificial lighting.
-l num
Set the blue scaling. The default is 1.0. The red and blue scal‐
ing factors are typically used to compensate for artificial light‐
ing.
-B num
This option may be used to set the thermal noise compensation. The
only valid values are 0 or 1. The default is 1, enabling compensa‐
tion. Setting this option to zero disables thermal noise compensa‐
tion. Thermal noise produces a baseline value for the CCD pixels.
The actual CCD data contains a 'black border' area on all four
sides which the processing program uses to determine the baseline.
The baseline is then subtracted from the data. It is not typically
useful to disable noise compensation.
-L num
Set the lowlight compensation factor. The default is 16. A value
of 0 will disable lowlight compensation. Lowlight compensation
changes the bleedover in the weighted compensation algorithm used
to generate the missing colors in the output photo. The higher the
value, the more of an 'averaging' effect we get (the weighting
becomes less important). The result is a softening of the edge
enhancement processing and more blending of adjacent pixels, reduc‐
ing the apparent noise in the output image when you view it. Low‐
light compensation does not seem to adversely effect normal photos
so the default is set fairly high.
-bw Black-and-white output. This only works for .ppm image output.
The magnitude is calculated and stored into all three color guns to
produce a black and white picture.
-inside
-indoor
Set the red scale to 0.7 to compensate for indoor lighting (same as
using -r 0.7). If not specified we assume outdoor lighting (par
1.0 for red and blue scale options).
-2 Generate a 24-bit PPM file (default)
-3 Generate a 48-bit PSD (Adobe Photoshop) file
-4 Generate a 48-bit PNG
files
Specify one or more files to process. Unless -c is specified crw
will generate an output file named after the input file with an
appropriate extension change.
SEE ALSO
/usr/ports/graphics/s10sh
HISTORY
The crw utility was created by Dave Coffin in 1997. Matt Dillon reworked
the main interpolation algorithm extensively in this port and is cur‐
rently maintaining it for FreeBSD.
4th Berkeley Distribution June 16, 2002 4th Berkeley Distribution
