src/contrast.c

   1 /* libSoX effect: Contrast Enhancement    (c) 2008 robs@users.sourceforge.net
   2  *
   3  * This library is free software; you can redistribute it and/or modify it
   4  * under the terms of the GNU Lesser General Public License as published by
   5  * the Free Software Foundation; either version 2.1 of the License, or (at
   6  * your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  16  */
  17
  18 #include "sox_i.h"
  19
  20 typedef struct {double contrast;} priv_t;
  21
  22 static int create(sox_effect_t * effp, int argc, char * * argv)
  23 {
  24   priv_t * p = (priv_t *)effp->priv;
  25   p->contrast = 75;
  26   --argc, ++argv;
  27   do {NUMERIC_PARAMETER(contrast, 0, 100)} while (0);
  28   p->contrast /= 750; /* shift range to 0 to 0.1333, default 0.1 */
  29   return argc? lsx_usage(effp) : SOX_SUCCESS;
  30 }
  31
  32 static int flow(sox_effect_t * effp, const sox_sample_t * ibuf,
  33     sox_sample_t * obuf, size_t * isamp, size_t * osamp)
  34 {
  35   priv_t * p = (priv_t *)effp->priv;
  36   size_t len = *isamp = *osamp = min(*isamp, *osamp);
  37   while (len--) {
  38     double d = *ibuf++ * (-M_PI_2 / SOX_SAMPLE_MIN);
  39     *obuf++ = sin(d + p->contrast * sin(d * 4)) * SOX_SAMPLE_MAX;
  40   }
  41   return SOX_SUCCESS;
  42 }
  43
  44 sox_effect_handler_t const * lsx_contrast_effect_fn(void)
  45 {
  46   static sox_effect_handler_t handler = {"contrast", "[enhancement (75)]",
  47     0, create, NULL, flow, NULL, NULL, NULL, sizeof(priv_t)};
  48   return &handler;
  49 }