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<h1>LibRaw: Usage Examples</h1>
<h2>Overview of Examples in the Distribution Package (samples/*)</h2>
<p>The LibRaw package contains several examples illustrating the use of this library.
Their source codes are located in the samples/ folder, and after library build they will be in the bin/ folder:</p>
<ul>
<li><b>raw-identify</b> The only LibRaw call it uses is <a href="API-CXX-eng.html#open_file">open_file()</a>;
further code prints the values of the fields of the imgdata structure. The output of
<b>raw-identify</b>/<b>raw-identify -v</b> is virtually identical to the output of
<b>dcraw -i</b>/<b>dcraw -i -v </b> (in the output of this example, the sources of color data in the numeric
form are additionally printed). Command line key <b>-u</b> shows unpacking function name.
</li>
<li><b>simple_dcraw</b> A simple "emulation" of dcraw reproducing the behavior of
<b>dcraw [-D] [-e] [-v] [-T]</b>. The result of its work must be binary identical to the result produced by a
dcraw run with relevant keys. A simplified version of this example is <a href="#code">considered below</a>.
<br/>
<b>-B</b> command-line switch turns on use of <a href="API-CXX-eng.html#open_buffer">open_buffer() API call</a>
used via mmap() of input file (Unix only).
</li>
<li><b>dcraw_half</b> Demonstrates the use of <a href="API-C-eng.html">C API</a>. The example emulates the
behavior of <b>dcraw -h</b> (no other control parameters can be specified in this example). The result of its
work must be binary identical to the results produced by <b>dcraw -h</b>.
</li>
<li><b>dcraw_emu</b> Complete emulation of dcraw (except for keys -D -d -P -K -i -e, which are considered in
other usage examples). Of most interest is processing of command line keys (copied from dcraw). The result of
its work must be binary identical to the results produced by dcraw with the same command line keys.
<br/>
This sample supports gamma-corrected output of 16-bit data (use <b>-1</b> command-line switch).
<br/>
<b>-B</b> command-line switch turns on use of <a href="API-CXX-eng.html#open_buffer">open_buffer() API call</a>
used via mmap() of input file (Unix only).
<br/>
The <b>-c float-value</b> command-line switch sets params.adjust_maximum value to nondefault.
Set it to zero to disable maximum adjustment and to nonzero to enable it. Disabling this feature
may result to incorrect highlights processing on some cameras.
</li>
<li><b>half_mt</b> Emulation of <b>dcraw -h</b>. It "understands" the following keys: -a (automatic
white balance over the entire image), -w (white balance of the camera), -T (output in the tiff format), and -J
n (number of parallel threads launched for image processing).<br/>
On multiprocessor/multicore computers, the speed gain is notable in the case of mass processing. On a
Win32 machine, the example is assembled from the initial file half_mt_win32.c, since
work with threads under Windows is fundamentally different and it it easier to copy simple source codes
than write one complex code.
</li>
<li><b>mem_image</b> This sample uses
<a href="API-CXX-eng.html#dcraw_make_mem_image">dcraw_make_mem_image</a> and
<a href="API-CXX-eng.html#dcraw_make_mem_thumb">dcraw_make_mem_thumb</a> calls, than writes data in PPM
format. Results should be identical with dcraw with same command-line options (options supported:
<b>-4, -1, -e, -h</b>).
</li>
<li><b>unprocessed_raw</b> This sample extracts (mostly) unaltered RAW data including masked pixels
data (on supported cameras). Black level subtraction and zero pixel averaging is turned off.
If black frame exists and black frame extraction is supported for given format, masked pixels
data is added to resulting .TIFF file.
Command line options: <b>-q</b> - be quiet, <b>-A</b> - autoscale data (integer multiplier),
<b>-g</b> gamma-correction (gamma 2.2) for data (instead of precise linear one), <b>-N</b> turns off tone
curve correction of RAW data.
</li>
<li><b>4channnels</b> - splits RAW-file into four separate 16-bit grayscale TIFFs (per RAW channel).<br/>
Command line switches:
<ul>
<li><b>-s N</b> selects N-th image from RAW with multiple images</li>
<li><b>-g</b> gamma correction (gamma 2.2)</li>
<li><b>-A</b> values autoscale by auto-calculated integer factor</li>
<li><b>-B</b> turn off black subtraction</li>
<li><b>-N</b> no RAW curve </li>
</ul>
</li>
</ul>
<h2>Example of docmode</h2>
<p>Below we consider the samples/simple_dcraw.cpp example, which emulates the behavior of
<b>dcraw [-D] [-e][-v][-t]</b>. To save space, let us assume that keys -t -v are always specified (to avoid
comments on command line parsing) and there is always one parameter (name of file), which is the only one and
always passed to the program.
</p>
<pre>
int main(int ac, char *av[])
{
int i, ret, verbose=0, output_thumbs=0;
char outfn[1024],thumbfn[1024];
// Creation of image processing object
LibRaw RawProcessor;
// The date in TIFF is written in the local format; let us specify the timezone for compatibility with dcraw
putenv ((char*)"TZ=UTC");
// Let us define variables for convenient access to fields of RawProcessor
#define P1 RawProcessor.imgdata.idata
#define S RawProcessor.imgdata.sizes
#define C RawProcessor.imgdata.color
#define T RawProcessor.imgdata.thumbnail
#define P2 RawProcessor.imgdata.other
#define OUT RawProcessor.imgdata.params
OUT.output_tiff = 1; // Let us output TIFF
// Let us open the file
if( (ret = RawProcessor.open_file(av[1])) != LIBRAW_SUCCESS)
{
fprintf(stderr,"Cannot open %s: %s\n",av[i],libraw_strerror(ret));
// recycle() is needed only if we want to free the resources right now.
// If we process files in a cycle, the next open_file()
// will also call recycle(). If a fatal error has happened, it means that recycle()
// has already been called (repeated call will not cause any harm either).
RawProcessor.recycle();
goto end;
}
// Let us unpack the image
if( (ret = RawProcessor.unpack() ) != LIBRAW_SUCCESS)
{
fprintf(stderr,"Cannot unpack_thumb %s: %s\n",av[i],libraw_strerror(ret));
if(LIBRAW_FATAL_ERROR(ret))
goto end;
// if there has been a non-fatal error, we will try to continue
}
// Let us unpack the thumbnail
if( (ret = RawProcessor.unpack_thumb() ) != LIBRAW_SUCCESS)
{
// error processing is completely similar to the previous case
fprintf(stderr,"Cannot unpack_thumb %s: %s\n",av[i],libraw_strerror(ret));
if(LIBRAW_FATAL_ERROR(ret))
goto end;
}
else // We have successfully unpacked the thumbnail, now let us write it to a file
{
snprintf(thumbfn,sizeof(thumbfn),"%s.%s",av[i],T.tformat == LIBRAW_THUMBNAIL_JPEG ? "thumb.jpg" : "thumb.ppm");
if( LIBRAW_SUCCESS != (ret = RawProcessor.dcraw_thumb_writer(thumbfn)))
{
fprintf(stderr,"Cannot write %s: %s\n",thumbfn,libraw_strerror(ret));
// in the case of fatal error, we should terminate processing of the current file
if(LIBRAW_FATAL_ERROR(ret))
goto end;
}
}
// Data unpacking
if(OUT.document_mode)
ret = RawProcessor.dcraw_document_mode_processing();
else
ret = RawProcessor.dcraw_process();
if(LIBRAW_SUCCESS != ret ) // error at the previous step
{
fprintf(stderr,"Cannot do postprocessing on %s: %s\n",av[i],libraw_strerror(ret));
if(LIBRAW_FATAL_ERROR(ret))
goto end;
}
else // Successful document processing
{
snprintf(outfn,sizeof(outfn),"%s.%s", av[i], "tiff");
if( LIBRAW_SUCCESS != (ret = RawProcessor.dcraw_ppm_tiff_writer(outfn)))
fprintf(stderr,"Cannot write %s: error %d\n",outfn,ret);
}
// we don't evoke recycle() or call the desctructor; C++ will do everything for us
return 0;
end:
// got here after an error
return 1;
}
</pre>
<a href=index-eng.html>[back to Index]</a>
<hr>
<address><a href="mailto:info@libraw.org">LibRaw Team</a></address>
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Last modified: Fri Apr 9 12:39:43 MSD 2010
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