void preprocessing_niblack(gy_image_object &img, int window_size)
{
int w = img.width(),h = img.height(),i,j,x1,x2,y1,y2,pix,sum,sd;
int *QS;
long long int *PWQS,pwsum;
QS = (int*) malloc (w * h * sizeof(int));
PWQS = (long long int*) malloc (w * h * sizeof(long long int));
for(i = 0; i < w; i++)
{
for(j = 0; j < h; j++)
{
QS[i * h + j] = img.get_pixel(i,j);
PWQS[i * h + j] = (long long int)img.get_pixel(i,j);
PWQS[i * h + j] *= PWQS[i * h + j];
}
}
for(i = 0; i < w; i++)
{
for(j = 1; j < h; j++)
{
QS[i * h + j] += QS[i * h + j - 1];
PWQS[i * h + j] += PWQS[i * h + j - 1];
}
}
for(i = 1; i < w; i++)
{
for(j = 0; j < h; j++)
{
QS[i * h + j] += QS[(i - 1) * h + j];
PWQS[i * h + j] += PWQS[(i - 1) * h + j];
}
}
for(i = 0; i < w; i++)
{
for(j = 0; j < h; j++)
{
x1 = i - window_size;
x2 = i + window_size;
y1 = j - window_size;
y2 = j + window_size;
if(x1 < 0)
{
x1 = -1;
}
if(y1 < 0)
{
y1 = -1;
}
if(x2 >= w)
{
x2 = w - 1;
}
if(y2 >= h)
{
y2 = h - 1;
}
pix = (x2 - x1) * (y2 - y1);
sum = QS[x2 * h + y2];
pwsum = PWQS[x2 * h + y2];
if(x1 >= 0)
{
sum -= QS[x1 * h + y2];
pwsum -= PWQS[x1 * h + y2];
}
if(y1 >= 0)
{
sum -= QS[x2 * h + y1];
pwsum -= PWQS[x2 * h + y1];
}
if(x1 >= 0 && y1 >= 0)
{
sum += QS[x1 * h + y1];
pwsum += PWQS[x1 * h + y1];
}
sd = (int)sqrt(((long long int)pwsum - (2 * (long long int)sum * (long long int)sum / (long long int)pix)) / (long long int)pix + ((long long int)sum * (long long int)sum / (long long int)pix / (long long int)pix));
(img.get_pixel(i,j) < sum / pix - (int)((double)1.3 * (double)sd))? img.set_pixel(i,j,0): img.set_pixel(i,j,255);
}
}
}
//run median filter of img with window size window_size
void preprocessing_median_filter(gy_image_object &img, int window_size)
{
int w = img.width(),h = img.height(),i,j,*QS,sum;
QS = (int*) malloc (w * h * sizeof(int));
for(i = 0; i < w; i++)
{
for(j = 0; j < h; j++)
{
QS[i * h + j] = (img.get_pixel(i,j) == 0)? 1: 0;
}
}
for(i = 0; i < w; i++)
{
for(j = 1; j < h; j++)
{
QS[i * h + j] += QS[i * h + j - 1];
}
}
for(i = 1; i < w; i++)
{
for(j = 0; j < h; j++)
{
QS[i * h + j] += QS[(i - 1) * h + j];
}
}
window_size--;
img.resize(w - window_size,h - window_size);
for(i = 0; i < w - window_size; i++)
{
for(j = 0; j < h - window_size; j++)
{
sum = QS[(i + window_size) * h + j + window_size];
//printf("sum = QS[%d][%d] = %d\n",i + window_size,j + window_size,QS[(i + window_size) * h + j + window_size]);
if(j > 0)
{
sum -= QS[(i + window_size) * h + j - 1];
//printf("sum -= QS[%d][%d]\n",i + window_size,j - 1);
}
if(i > 0)
{
sum -= QS[(i - 1) * h + j + window_size];
//printf("sum -= QS[%d][%d]\n",i - 1,j + window_size);
}
if(i > 0 && j > 0)
{
sum += QS[(i - 1) * h + j - 1];
//printf("sum += QS[%d][%d]\n",i - 1,j - 1);
}
//printf("<%d,%d> = %d\n",i,j,sum);
img.set_pixel(i,j,(sum < (window_size + 1) * (window_size + 1) >> 1)? 255: 0);
}
}
free(QS);
}