Better parsing of number of levels

posterize.c

@@ -58,7 +58,7 @@ static void interpolate_palette_front(const palette *pal, unsigned int mapping[]
 static void voronoi(const hist_entry histogram[static 256], palette *pal);
 static double palette_error(const hist_entry histogram[static 256], const palette *palette_orig);
 static void interpolate_palette_back(const palette *pal, unsigned int mapping[]);
-static void posterize(png24_image *img, unsigned int maxcolors, const double maxerror, bool dither, bool verbose);
+static void posterize(png24_image *img, unsigned int maxlevels, const double maxerror, bool dither, bool verbose);
 
 inline static double int_to_linear(unsigned int value)
 {
@@ -184,7 +184,7 @@ static void palette_from_boxes(const struct box boxes[], const int numboxes, con
 /*
  1-dimensional median cut, using variance for "largest" box
 */
-static unsigned int reduce(const unsigned int maxcolors, const double maxerror, const hist_entry histogram[static 256], palette *pal)
+static unsigned int reduce(const unsigned int maxlevels, const double maxerror, const hist_entry histogram[static 256], palette *pal)
 {
  unsigned int numboxes=1;
  struct box boxes[256];
@@ -196,7 +196,7 @@ static unsigned int reduce(const unsigned int maxcolors, const double maxerror,
  for(unsigned int i=boxes[0].start; i < boxes[0].end; i++) boxes[0].sum += BOTH(histogram[i]);
  boxes[0].variance = 1; // irrelevant for first box
 
- while(numboxes < maxcolors) {
+ while(numboxes < maxlevels) {
  int boxtosplit=-1;
  double largest=0;
  // pick box to split by choosing one with highest variance
@@ -446,13 +446,18 @@ int main(int argc, char *argv[])
  }
  int argn = optind;
 
- int maxcolors = maxerror > 0 ? 255 : 0;
- if (argc==(argn+1)) {
- maxcolors=atoi(argv[argn]);
- argn++;
+ int maxlevels = maxerror > 0 ? 255 : 0;
+
+ if (argn < argc) {
+ char *levels_end;
+ unsigned long levels = strtoul(argv[argn], &levels_end, 10);
+ if (levels_end != argv[argn] && '\0' == levels_end[0]) {
+ maxlevels = levels;
+ argn++;
+ }
  }
 
- if (argc != argn || maxcolors < 2 || maxcolors > 255) {
+ if (argc != argn || maxlevels < 2 || maxlevels > 255) {
  usage(argv[0]);
  return 1;
  }
@@ -469,7 +474,7 @@ int main(int argc, char *argv[])
  }
  image_gamma = 1.0/img.gamma;
 
- posterize(&img, maxcolors, maxerror, dither, verbose);
+ posterize(&img, maxlevels, maxerror, dither, verbose);
 
  if ((retval = rwpng_write_image24(stdout, &img))) {
  fprintf(stderr, "Error: cannot write PNG to stdout\n");
@@ -480,25 +485,25 @@ int main(int argc, char *argv[])
 }
 
 
-static void posterize(png24_image *img, unsigned int maxcolors, const double maxerror, bool dither, bool verbose)
+static void posterize(png24_image *img, unsigned int maxlevels, const double maxerror, bool dither, bool verbose)
 {
  hist_entry histogram[256]={{0}};
  intensity_histogram(img, histogram);
 
  // reserve colors for black and white
  // and omit them from histogram to avoid confusing median cut
  unsigned int reservedcolors=0;
- if (BOTH(histogram[0]) >= 1.0 && maxcolors > 2) {
- maxcolors--;reservedcolors++;
+ if (BOTH(histogram[0]) >= 1.0 && maxlevels > 2) {
+ maxlevels--;reservedcolors++;
  histogram[0]=(hist_entry){0,0};
  }
- if (BOTH(histogram[255]) >= 1.0 && maxcolors > 2) {
- maxcolors--;reservedcolors++;
+ if (BOTH(histogram[255]) >= 1.0 && maxlevels > 2) {
+ maxlevels--;reservedcolors++;
  histogram[255]=(hist_entry){0,0};
  }
 
  palette pal;
- unsigned int levels = reduce(maxcolors, maxerror, histogram, &pal);
+ unsigned int levels = reduce(maxlevels, maxerror, histogram, &pal);
 
  double last_err = INFINITY;
  for(unsigned int j=0; j < 100; j++) {