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#import <stdlib.h>
#import <stdint.h>
#import <assert.h>
#import <math.h>
#import <unistd.h>
#import "GrayMap.h"
enum
{
kDownscale = 16,
kHalfDownscale = kDownscale / 2,
kThreshold = 128
};
static void PerformDistanceMapping(GrayMap *source, GrayMap *dmap, GrayMap *amap);
static void DistanceMapOnePixel(GrayMap *source, GrayMap *dmap, GrayMap *amap, uint32_t x, uint32_t y);
static bool wrap = false;
static inline uint32_t RoundSize(uint32_t size)
{
return (size + kDownscale - 1) / kDownscale;
}
int main (int argc, char * argv[])
{
GrayMap *source = NULL;
GrayMap *dmap = NULL;
GrayMap *amap = NULL;
bool printUsage = false;
bool angleMap = false;
// Get options
for (;;)
{
int option = getopt(argc, argv, "wa");
if (option == -1) break;
switch (option)
{
case 'w':
wrap = true;
break;
case 'a':
angleMap = true;
break;
default:
printUsage = true;
}
}
if (argc <= optind) printUsage = true;
if (printUsage)
{
fprintf(stderr, "Usage: %s [-w] <filename.png>\n", argv[0]);
return EXIT_FAILURE;
}
source = ReadGrayMap(argv[optind]);
if (source == NULL) return EXIT_FAILURE;
dmap = NewGrayMap(RoundSize(source->width), RoundSize(source->height), 0);
if (angleMap) amap = NewGrayMap(RoundSize(source->width), RoundSize(source->height), 0);
if (dmap == NULL || (angleMap && amap == NULL))
{
fprintf(stderr, "Could not allocate memory for output image.\n");
return EXIT_FAILURE;
}
PerformDistanceMapping(source, dmap, amap);
WriteGrayMap("distance_map.png", dmap);
if (angleMap) WriteGrayMap("angle_map.png", amap);
return 0;
}
static void PerformDistanceMapping(GrayMap *source, GrayMap *dmap, GrayMap *amap)
{
uint32_t width, height, x, y;
assert(source && dmap);
width = dmap->width;
height = dmap->height;
for (y = 0; y != height; ++y)
{
for (x = 0; x != width; ++x)
{
DistanceMapOnePixel(source, dmap, amap, x, y);
}
putchar('.');
fflush(stdout);
}
}
static bool ReadPx(GrayMap *source, uint32_t x, uint32_t y, int16_t dx, int16_t dy);
static inline int32_t Max(int32_t a, int32_t b)
{
return (a > b) ? a : b;
}
static inline int32_t Min(int32_t a, int32_t b)
{
return (a < b) ? a : b;
}
static inline int32_t Abs(int32_t a)
{
return (a >= 0) ? a : -a;
}
static void DistanceMapOnePixel(GrayMap *source, GrayMap *dmap, GrayMap *amap, uint32_t x, uint32_t y)
{
int32_t dx, dy;
bool target;
uint32_t distanceSq, bestDistanceSq = UINT32_MAX;
uint32_t bestDistance;
float bestAngle;
uint32_t currDistance, maxDistance = Max(source->width, source->height);
int8_t ddx = 1, ddy = 0, ddt;
uint8_t countdown = 3;
uint32_t i, length = 2;
int32_t bestDx = 1, bestDy = 1;
dx = 0;
dy = -1;
if (amap == NULL) maxDistance = Min(maxDistance, 128);
target = !ReadPx(source, x, y, 0, 0);
for (;;)
{
// Spiral outwards.
do
{
for (i = 0; i < length; i++)
{
if (ReadPx(source, x, y, dx, dy) == target)
{
distanceSq = dx * dx + dy * dy;
if (distanceSq < bestDistanceSq)
{
bestDistanceSq = distanceSq;
bestDx = dx;
bestDy = dy;
}
}
dx += ddx;
dy += ddy;
}
// Turn a corner.
ddt = ddx;
ddx = -ddy;
ddy = ddt;
}
while (--countdown);
currDistance = Max(Abs(dx), Abs(dy));
if ((currDistance * currDistance) > bestDistanceSq || currDistance > maxDistance) break;
countdown = 2;
length++;
}
bestDistance = sqrt(bestDistanceSq);
if (target)
{
if (bestDistance > 128) bestDistance = 0;
else bestDistance = 128 - bestDistance;
bestDx = -bestDx;
bestDy = -bestDy;
}
else
{
bestDistance = 127 + bestDistance;
if (bestDistance > 255) bestDistance = 255;
}
GrayMapSet(dmap, x, y, bestDistance);
if (amap != NULL)
{
bestAngle = atan2(bestDx, bestDy);
bestAngle = (bestAngle + M_PI) * 127.5 / M_PI; // Convert from +/-pi to 0..255
GrayMapSet(amap, x, y, bestAngle);
}
}
static bool ReadPx(GrayMap *source, uint32_t x, uint32_t y, int16_t dx, int16_t dy)
{
int32_t ax = x * kDownscale + dx - kHalfDownscale;
int32_t ay = y * kDownscale + dy - kHalfDownscale;
if (wrap)
{
ax = ax % source->width;
if (ax < 0) ax += source->width;
ay = ay % source->height;
if (ay < 0) ay += source->height;
}
return GrayMapGet(source, ax, ay) >= kThreshold;
}
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