Overview of Examples in the Distribution Package (samples/*)

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:

• identify The only LibRaw call it uses is open_file(); further code prints the values of the fields of the imgdata structure. The output of identify/identify -v is virtually identical to the output of dcraw -i/dcraw -i -v (in the output of this example, the sources of color data in the numeric form are additionally printed).
• simple_dcraw A simple "emulation" of dcraw reproducing the behavior of dcraw [-D] [-e] [-v] [-T]. 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 considered below.
• dcraw_half Demonstrates the use of C API. The example emulates the behavior of dcraw -h (no other control parameters can be specified in this example). The result of its work must be binary identical to the results produced by dcraw -h.
• dcraw_emu 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.
  This sample supports gamma-corrected output of 16-bit data (use -1 command-line switch).
• half_mt Emulation of dcraw -h. 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).
  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.
• mem_image Sample of usage memory-writing functions: dcraw_make_mem_image and dcraw_make_mem_thumb. Result should be identical to dcraw with same command-line keys(supported keys: -4, -1, -e, -h).
• unprocessed_raw 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: -q - be quiet, -A - autoscale data (integer multiplier), -g gamma-correction (gamma 2.2) for data (instead of precise linear one)..

Example of docmode

Below we consider the samples/simple_dcraw.cpp example, which emulates the behavior of dcraw [-D] [-e][-v][-t]. 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.

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;
}