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////////////////////////////////////////////////////////////////////////////////////////////////
// count neighbors
int count_neighbors(Rasterimage* raster,int i,int j){
int count;
// count neighbors
count=0;
if(raster->getPixel(i,j-1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i+1,j-1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i+1,j)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i+1,j+1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i,j+1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i-1,j+1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i-1,j)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i-1,j-1)!=raster->getBackground()){
count++;
}
// return count
return count;
}
////////////////////////////////////////////////////////////////////////////////////////////////
// ccount zero-to-one transitions
int count_transitions(Rasterimage* raster,int i,int j){
int count;
// count zero-to-one transitions
count=0;
if(raster->getPixel(i,j-1)==raster->getBackground() && raster->getPixel(i+1,j-1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i+1,j-1)==raster->getBackground() && raster->getPixel(i+1,j)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i+1,j)==raster->getBackground() && raster->getPixel(i+1,j+1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i+1,j+1)==raster->getBackground() && raster->getPixel(i,j+1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i,j+1)==raster->getBackground() && raster->getPixel(i-1,j+1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i-1,j+1)==raster->getBackground() && raster->getPixel(i-1,j)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i-1,j)==raster->getBackground() && raster->getPixel(i-1,j-1)!=raster->getBackground()){
count++;
}
if(raster->getPixel(i-1,j-1)==raster->getBackground() && raster->getPixel(i,j-1)!=raster->getBackground()){
count++;
}
// return count
return count;
}
////////////////////////////////////////////////////////////////////////////////////////////////
// check boundary at south-east
int check_se(Rasterimage* raster,int i,int j){
int count;
// check neighbors
count=count_neighbors(raster,i,j);
if(count < 2 || count > 6){
return 0;
}
// check zero-to-one transitions
count=count_transitions(raster,i,j);
if(count != 1){
return 0;
}
// check east
if(raster->getPixel(i,j-1)!=raster->getBackground() &&
raster->getPixel(i+1,j)!=raster->getBackground() &&
raster->getPixel(i,j+1)!=raster->getBackground() ){
return 0;
}
// check south
if(raster->getPixel(i+1,j)!=raster->getBackground() &&
raster->getPixel(i,j+1)!=raster->getBackground() &&
raster->getPixel(i-1,j)!=raster->getBackground() ){
return 0;
}
// return true
return 1;
}
////////////////////////////////////////////////////////////////////////////////////////////////
// check boundary at north-west
int check_nw(Rasterimage* raster,int i,int j){
int count;
// check neighbors
count=count_neighbors(raster,i,j);
if(count < 2 || count > 6){
return 0;
}
// check zero-to-one transition
count=count_transitions(raster,i,j);
if(count != 1){
return 0;
}
// check north
if(raster->getPixel(i,j-1)!=raster->getBackground() &&
raster->getPixel(i+1,j)!=raster->getBackground() &&
raster->getPixel(i-1,j)!=raster->getBackground() ){
return 0;
}
// check west
if(raster->getPixel(i,j-1)!=raster->getBackground() &&
raster->getPixel(i,j+1)!=raster->getBackground() &&
raster->getPixel(i-1,j)!=raster->getBackground() ){
return 0;
}
// return true
return 1;
}
////////////////////////////////////////////////////////////////////////////////////////////////
//! Zhang-Suen skeletonizing
/*!
Uses the Zhang-Suen skeletonizing algorithm to get the skeletons
of objects in a binary image.
\param raster A binarized Rasterimage
\return The medial axes transformed Rasterimage
*/
Rasterimage* skel_zhang_suen(Rasterimage* raster){
int i,j,changes;
int width,height;
unsigned char background;
Rasterimage* tmp_raster;
// set size
width=raster->getWidth();
height=raster->getHeight();
// background color
background=raster->getBackground();
// allocate memory / make new raster
tmp_raster=new Rasterimage(raster->getWidth(),raster->getHeight(),raster->getColors(),raster->getType());
// set colors
for (i=0; i<(int)raster->getColors();i++){
tmp_raster->setColorPalette(i,raster->getColorPalette(i));
}
tmp_raster->setBackground(background);
// calculate skeleton / first iteration
for (j=0;j<height;j++){
for (i=0;i<width;i++){
if(i>0 && j>0 && i<width-1 && j<height-1 && raster->getPixel(i,j)!=background){
if( check_se(raster,i,j) ){
// set white if not skeleton
tmp_raster->setPixel(i,j,background);
}else{
// set old color
tmp_raster->setPixel(i,j,raster->getPixel(i,j));
tmp_raster->incrPointcount();
}
}else{
// set white if not point or border
tmp_raster->setPixel(i,j,background);
}
;
}
}
// calculate skeleton / second iteration
for (j=0;j<height;j++){
for (i=0;i<width;i++){
if(i>0 && j>0 && i<width-1 && j<height-1 && raster->getPixel(i,j)!=background){
if( check_nw(raster,i,j) ){
// set white if not skeleton
tmp_raster->setPixel(i,j,background);
}else{
// set old color
tmp_raster->setPixel(i,j,raster->getPixel(i,j));
tmp_raster->incrPointcount();
}
}else{
// set white if not point or border
tmp_raster->setPixel(i,j,background);
}
;
}
}
// check changes
changes=0;
for (j=0;j<height;j++){
for (i=0;i<width;i++){
if(raster->getPixel(i,j)!=tmp_raster->getPixel(i,j)){
changes=1;
}
}
}
// free memory
delete raster;
// if changes, do it again
if(changes){
return skel_zhang_suen(tmp_raster);
}else{
// return raster
return tmp_raster;
}
} |
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