/***********************************************
*
* perform_convolution (...
*
* This function performs convolution
* between the input image and 8 3x3 masks.
* The result is placed in the out_image.
*
***********************************************/
perform_convolution(image, out_image,
detect_type, threshold,
image_header, high)
short image[ROWS][COLS],
out_image [ROWS][COLS];
int detect_type, high, threshold;
struct tiff_header_struct *image_header;
{
int a,
b,
i,
is_present,
j,
sum;
short mask_0[3][3],
mask_1[3][3],
mask_213][3],
mask_3[3][3],
mask_4[3][3],
mask_5[3][3],
mask_6[3][3],
mask_7[3][3],
max,
min,
new_hi,
new_low;
setup_masks(detect_type, mask_0, mask_1,
mask_2, mask_3, mask_4, mask_5,
mask_6, mask_7);
new_hi = 250;
new_low = 16;
if (image_header->bits_per_pixel == 4){
new_hi = 10;
new_low = 3;
}
min = 0;
max = 225;
if(image_header->bits_per_pixel == 4)
max = 16;
/* clear output image array */
for(i-0; i<ROWS; i++)
for(j=0; j<COLS; j++)
out_image[i][j] = 0;
printf("\n ");
for(i=1; i<ROWS-1; i++){
if( (i%10) == 0) printf("%3d", i);
for(j=1; j<COLS-1; j++){
/* Convolve for all 8 directions */
/* 0 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++){
sum = sum + image[i+a][j+b] *
mask_0[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
/**/
/**/
/**/
if(sum > out_image[i][j]) /**************/
out_image[i][j] = sum; /**************/
/**/
/**/
/**/
/* 1 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++) {
sum = sum + image[i+a][j+b] * mask_1[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
/* 2 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++) {
sum = sum + image[i+a][j+b] * mask_2[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
/* 3 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++){
sum = sum + image[i+a][j+b] * mask_3[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
/* 4 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++){
sum = sum + image[i+a][j+b] * mask_4[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
/* 5 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++){
sum = sum + image[i+a][j+b] * mask_5[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
/* 6 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++){
sum = sum + image[i+a][j+b] * mask_6[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
/* 7 direction */
sum = 0;
for(a=-1; a<2; a++){
for(b=-1; b<2; b++){
sum = sum + image[i+a][j+b] * mask_7[a+1][b+1];
}
}
if(sum > max) sum = max;
if(sum < 0) sum = 0;
/* Correction 12-27-92 see file header for details. */
if(sum > out_image[i][j])
out_image[i][j] = sum;
} /* ends loop over j */
} /* ends loop over i */
/* if desired, threshold the output image */
if(threshold == 1){
for(i=0; i<ROWS; i++){
for(j=0; j<COLS; j++){
if(out_image[i][j] > high) {
out_image[i][j] = new_hi;
}
else{
out_image[i][j] = new_low;
}
}
}
} /* ends if threshold == 1 */
} /* ends perform_convolution */
/* End of File */