/* libSoX effect: Contrast Enhancement    (c) 2008 robs@users.sourceforge.net * * This library is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or (at * your option) any later version. * * This library is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser * General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this library; if not, write to the Free Software Foundation, * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA */ #include "sox_i.h" typedef struct {double contrast;} priv_t; static int soxcreate(sox_effect_t * effp, int argc, char * * argv){  priv_t * p = (priv_t *)effp->priv;  p->contrast = 75;  --argc, ++argv;  do {NUMERIC_PARAMETER(contrast, 0, 100); USED(argv);} while (0);  p->contrast /= 750; /* shift range to 0 to 0.1333, default 0.1 */  return argc? lsx_usage(effp) : SOX_SUCCESS;} static int flow(sox_effect_t * effp, const sox_sample_t * ibuf,    sox_sample_t * obuf, size_t * isamp, size_t * osamp){  priv_t * p = (priv_t *)effp->priv;  size_t len = *isamp = *osamp = min(*isamp, *osamp);  while (len--) {    double d = *ibuf++ * (-M_PI_2 / SOX_SAMPLE_MIN);    *obuf++ = sin(d + p->contrast * sin(d * 4)) * SOX_SAMPLE_MAX;  }  return SOX_SUCCESS;} sox_effect_handler_t const * lsx_contrast_effect_fn(void){  static sox_effect_handler_t handler = {"contrast", "[enhancement (75)]",    0, soxcreate, NULL, flow, NULL, NULL, NULL, sizeof(priv_t)};  return &handler;}