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DEFINITIONS
This source file includes following definitions.
- cmpDistances
- buildDispersedMatrix
- buildClusteredMatrix
- distance
- buildSCDMatrix
- test
- isStatic
//========================================================================
//
// SplashScreen.cc
//
//========================================================================
#include <aconf.h>
#ifdef USE_GCC_PRAGMAS
#pragma implementation
#endif
#include <stdlib.h>
#include <string.h>
#include "gmem.h"
#include "SplashMath.h"
#include "SplashScreen.h"
//------------------------------------------------------------------------
static SplashScreenParams defaultParams = {
splashScreenDispersed, // type
2, // size
2, // dotRadius
1.0, // gamma
0.0, // blackThreshold
1.0 // whiteThreshold
};
//------------------------------------------------------------------------
struct SplashScreenPoint {
int x, y;
int dist;
};
static int cmpDistances(const void *p0, const void *p1) {
return ((SplashScreenPoint *)p0)->dist - ((SplashScreenPoint *)p1)->dist;
}
//------------------------------------------------------------------------
// SplashScreen
//------------------------------------------------------------------------
// If <clustered> is true, this generates a 45 degree screen using a
// circular dot spot function. DPI = resolution / ((size / 2) *
// sqrt(2)). If <clustered> is false, this generates an optimal
// threshold matrix using recursive tesselation. Gamma correction
// (gamma = 1 / 1.33) is also computed here.
SplashScreen::SplashScreen(SplashScreenParams *params) {
Guchar u, black, white;
int i;
if (!params) {
params = &defaultParams;
}
switch (params->type) {
case splashScreenDispersed:
// size must be a power of 2
for (size = 1; size < params->size; size <<= 1) ;
mat = (Guchar *)gmallocn(size * size, sizeof(Guchar));
buildDispersedMatrix(size/2, size/2, 1, size/2, 1);
break;
case splashScreenClustered:
// size must be even
size = (params->size >> 1) << 1;
if (size < 2) {
size = 2;
}
mat = (Guchar *)gmallocn(size * size, sizeof(Guchar));
buildClusteredMatrix();
break;
case splashScreenStochasticClustered:
// size must be at least 2*r
if (params->size < 2 * params->dotRadius) {
size = 2 * params->dotRadius;
} else {
size = params->size;
}
mat = (Guchar *)gmallocn(size * size, sizeof(Guchar));
buildSCDMatrix(params->dotRadius);
break;
}
// do gamma correction and compute minVal/maxVal
minVal = 255;
maxVal = 0;
black = splashRound((SplashCoord)255.0 * params->blackThreshold);
if (black < 1) {
black = 1;
}
white = splashRound((SplashCoord)255.0 * params->whiteThreshold);
if (white > 255) {
white = 255;
}
for (i = 0; i < size * size; ++i) {
u = splashRound((SplashCoord)255.0 *
splashPow((SplashCoord)mat[i] / 255.0, params->gamma));
if (u < black) {
u = black;
} else if (u >= white) {
u = white;
}
mat[i] = u;
if (u < minVal) {
minVal = u;
} else if (u > maxVal) {
maxVal = u;
}
}
}
void SplashScreen::buildDispersedMatrix(int i, int j, int val,
int delta, int offset) {
if (delta == 0) {
// map values in [1, size^2] --> [1, 255]
mat[i * size + j] = 1 + (254 * (val - 1)) / (size * size - 1);
} else {
buildDispersedMatrix(i, j,
val, delta / 2, 4*offset);
buildDispersedMatrix((i + delta) % size, (j + delta) % size,
val + offset, delta / 2, 4*offset);
buildDispersedMatrix((i + delta) % size, j,
val + 2*offset, delta / 2, 4*offset);
buildDispersedMatrix((i + 2*delta) % size, (j + delta) % size,
val + 3*offset, delta / 2, 4*offset);
}
}
void SplashScreen::buildClusteredMatrix() {
SplashCoord *dist;
SplashCoord u, v, d;
Guchar val;
int size2, x, y, x1, y1, i;
size2 = size >> 1;
// initialize the threshold matrix
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
mat[y * size + x] = 0;
}
}
// build the distance matrix
dist = (SplashCoord *)gmallocn(size * size2, sizeof(SplashCoord));
for (y = 0; y < size2; ++y) {
for (x = 0; x < size2; ++x) {
if (x + y < size2 - 1) {
u = (SplashCoord)x + 0.5 - 0;
v = (SplashCoord)y + 0.5 - 0;
} else {
u = (SplashCoord)x + 0.5 - (SplashCoord)size2;
v = (SplashCoord)y + 0.5 - (SplashCoord)size2;
}
dist[y * size2 + x] = u*u + v*v;
}
}
for (y = 0; y < size2; ++y) {
for (x = 0; x < size2; ++x) {
if (x < y) {
u = (SplashCoord)x + 0.5 - 0;
v = (SplashCoord)y + 0.5 - (SplashCoord)size2;
} else {
u = (SplashCoord)x + 0.5 - (SplashCoord)size2;
v = (SplashCoord)y + 0.5 - 0;
}
dist[(size2 + y) * size2 + x] = u*u + v*v;
}
}
// build the threshold matrix
minVal = 1;
maxVal = 0;
x1 = y1 = 0; // make gcc happy
for (i = 0; i < size * size2; ++i) {
d = -1;
for (y = 0; y < size; ++y) {
for (x = 0; x < size2; ++x) {
if (mat[y * size + x] == 0 &&
dist[y * size2 + x] > d) {
x1 = x;
y1 = y;
d = dist[y1 * size2 + x1];
}
}
}
// map values in [0, 2*size*size2-1] --> [1, 255]
val = 1 + (254 * (2*i)) / (2*size*size2 - 1);
mat[y1 * size + x1] = val;
val = 1 + (254 * (2*i+1)) / (2*size*size2 - 1);
if (y1 < size2) {
mat[(y1 + size2) * size + x1 + size2] = val;
} else {
mat[(y1 - size2) * size + x1 + size2] = val;
}
}
gfree(dist);
}
// Compute the distance between two points on a toroid.
int SplashScreen::distance(int x0, int y0, int x1, int y1) {
int dx0, dx1, dx, dy0, dy1, dy;
dx0 = abs(x0 - x1);
dx1 = size - dx0;
dx = dx0 < dx1 ? dx0 : dx1;
dy0 = abs(y0 - y1);
dy1 = size - dy0;
dy = dy0 < dy1 ? dy0 : dy1;
return dx * dx + dy * dy;
}
// Algorithm taken from:
// Victor Ostromoukhov and Roger D. Hersch, "Stochastic Clustered-Dot
// Dithering" in Color Imaging: Device-Independent Color, Color
// Hardcopy, and Graphic Arts IV, SPIE Vol. 3648, pp. 496-505, 1999.
void SplashScreen::buildSCDMatrix(int r) {
SplashScreenPoint *dots, *pts;
int dotsLen, dotsSize;
char *tmpl;
char *grid;
int *region, *dist;
int x, y, xx, yy, x0, x1, y0, y1, i, j, d, iMin, dMin, n;
//~ this should probably happen somewhere else
srand(123);
// generate the random space-filling curve
pts = (SplashScreenPoint *)gmallocn(size * size, sizeof(SplashScreenPoint));
i = 0;
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
pts[i].x = x;
pts[i].y = y;
++i;
}
}
for (i = 0; i < size * size; ++i) {
j = i + (int)((double)(size * size - i) *
(double)rand() / ((double)RAND_MAX + 1.0));
x = pts[i].x;
y = pts[i].y;
pts[i].x = pts[j].x;
pts[i].y = pts[j].y;
pts[j].x = x;
pts[j].y = y;
}
// construct the circle template
tmpl = (char *)gmallocn((r+1)*(r+1), sizeof(char));
for (y = 0; y <= r; ++y) {
for (x = 0; x <= r; ++x) {
tmpl[y*(r+1) + x] = (x * y <= r * r) ? 1 : 0;
}
}
// mark all grid cells as free
grid = (char *)gmallocn(size * size, sizeof(char));
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
grid[y*size + x] = 0;
}
}
// walk the space-filling curve, adding dots
dotsLen = 0;
dotsSize = 32;
dots = (SplashScreenPoint *)gmallocn(dotsSize, sizeof(SplashScreenPoint));
for (i = 0; i < size * size; ++i) {
x = pts[i].x;
y = pts[i].y;
if (!grid[y*size + x]) {
if (dotsLen == dotsSize) {
dotsSize *= 2;
dots = (SplashScreenPoint *)greallocn(dots, dotsSize,
sizeof(SplashScreenPoint));
}
dots[dotsLen++] = pts[i];
for (yy = 0; yy <= r; ++yy) {
y0 = (y + yy) % size;
y1 = (y - yy + size) % size;
for (xx = 0; xx <= r; ++xx) {
if (tmpl[yy*(r+1) + xx]) {
x0 = (x + xx) % size;
x1 = (x - xx + size) % size;
grid[y0*size + x0] = 1;
grid[y0*size + x1] = 1;
grid[y1*size + x0] = 1;
grid[y1*size + x1] = 1;
}
}
}
}
}
gfree(tmpl);
gfree(grid);
// assign each cell to a dot, compute distance to center of dot
region = (int *)gmallocn(size * size, sizeof(int));
dist = (int *)gmallocn(size * size, sizeof(int));
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
iMin = 0;
dMin = distance(dots[0].x, dots[0].y, x, y);
for (i = 1; i < dotsLen; ++i) {
d = distance(dots[i].x, dots[i].y, x, y);
if (d < dMin) {
iMin = i;
dMin = d;
}
}
region[y*size + x] = iMin;
dist[y*size + x] = dMin;
}
}
// compute threshold values
for (i = 0; i < dotsLen; ++i) {
n = 0;
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
if (region[y*size + x] == i) {
pts[n].x = x;
pts[n].y = y;
pts[n].dist = distance(dots[i].x, dots[i].y, x, y);
++n;
}
}
}
qsort(pts, n, sizeof(SplashScreenPoint), &cmpDistances);
for (j = 0; j < n; ++j) {
// map values in [0 .. n-1] --> [255 .. 1]
mat[pts[j].y * size + pts[j].x] = 255 - (254 * j) / (n - 1);
}
}
gfree(pts);
gfree(region);
gfree(dist);
gfree(dots);
}
SplashScreen::SplashScreen(SplashScreen *screen) {
size = screen->size;
mat = (Guchar *)gmallocn(size * size, sizeof(Guchar));
memcpy(mat, screen->mat, size * size * sizeof(Guchar));
minVal = screen->minVal;
maxVal = screen->maxVal;
}
SplashScreen::~SplashScreen() {
gfree(mat);
}
int SplashScreen::test(int x, int y, Guchar value) {
int xx, yy;
return 1;
if (value < minVal) {
return 0;
}
if (value >= maxVal) {
return 1;
}
if ((xx = x % size) < 0) {
xx = -xx;
}
if ((yy = y % size) < 0) {
yy = -yy;
}
return value < mat[yy * size + xx] ? 0 : 1;
}
GBool SplashScreen::isStatic(Guchar value) {
return value < minVal || value >= maxVal;
}