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Converted the internal representation of the labels from unsigned cha…
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…r to int, in order to support larger no of connected components.
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Saburo Okita authored and Saburo Okita committed Jun 7, 2014
1 parent 4963e5e commit b7fdc6c
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46 changes: 27 additions & 19 deletions ConnectedComponent/ConnectedComponent/ConnectedComponent.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,51 +7,59 @@
//

#include "ConnectedComponent.h"
#include <stdexcept>

using namespace std;
using namespace cv;

ConnectedComponent::ConnectedComponent(){
ConnectedComponent::ConnectedComponent( int max_component )
: maxComponent( max_component ){
}

ConnectedComponent::~ConnectedComponent(){
}

/**
* Apply connected component labelling
* it only works for maximum 255 connected components
* Apply connected component labeling
* it only works for predefined maximum no of connected components
* and currently treat black color as background
*/
Mat ConnectedComponent::apply( const Mat& image ) {
CV_Assert( image.type() == CV_8UC1 );

Mat result = image.clone();

/* First pass, labelling the regions incrementally */
result.convertTo( result, CV_32SC1 );

/* First pass, labeling the regions incrementally */
nextLabel = 1;
vector<uchar> linked(255);

uchar * prev_ptr = NULL;
vector<int> linked(maxComponent);
int * prev_ptr = NULL;
for( int y = 0; y < result.rows; y++ ) {
uchar * curr_ptr = result.ptr<uchar>(y);
int * curr_ptr = result.ptr<int>(y);

for( int x = 0; x < result.cols; x++ ) {

if( curr_ptr[x] != 0 ) {
vector<uchar> neighbors = getNeighbors( curr_ptr, prev_ptr, x, y, result.cols );
vector<int> neighbors = getNeighbors( curr_ptr, prev_ptr, x, y, result.cols );

if( neighbors.empty() ) {
curr_ptr[x] = nextLabel;
nextLabel++;

CV_Assert( nextLabel < 255 );
if( nextLabel >= maxComponent ) {
stringstream ss;
ss << "Current label count [" << (int) nextLabel
<< "] exceeds maximum no of components [" << maxComponent << "]";
throw std::runtime_error( ss.str() );
}
}
else {
/* Use the minimum label out from the neighbors */
int min_index = (int) (min_element( neighbors.begin(), neighbors.end() ) - neighbors.begin());
curr_ptr[x] = neighbors[min_index];

for( uchar neighbor: neighbors )
for( int neighbor: neighbors )
disjointUnion( curr_ptr[x], neighbor, linked );
}
}
Expand All @@ -61,9 +69,9 @@ Mat ConnectedComponent::apply( const Mat& image ) {

/* Second pass merge the equivalent labels */
nextLabel = 1;
vector<uchar> temp, labels_set(255);
vector<int> temp, labels_set(maxComponent);
for( int y = 0; y < result.rows; y++ ) {
uchar * curr_ptr = result.ptr<uchar>(y);
int * curr_ptr = result.ptr<int>(y);

for( int x = 0; x < result.cols; x++ ) {
if( curr_ptr[x] != 0 ) {
Expand Down Expand Up @@ -95,7 +103,7 @@ int ConnectedComponent::getComponentsCount() {
* Disjoint set union function, taken from
* https://courses.cs.washington.edu/courses/cse576/02au/homework/hw3/ConnectComponent.java
*/
void ConnectedComponent::disjointUnion( uchar a, uchar b, vector<uchar>& parent ) {
void ConnectedComponent::disjointUnion( int a, int b, vector<int>& parent ) {
while( parent[a] > 0 )
a = parent[a];
while( parent[b] > 0 )
Expand All @@ -113,7 +121,7 @@ void ConnectedComponent::disjointUnion( uchar a, uchar b, vector<uchar>& parent
* Disjoint set find function, taken from
* https://courses.cs.washington.edu/courses/cse576/02au/homework/hw3/ConnectComponent.java
*/
uchar ConnectedComponent::disjointFind( uchar a, vector<uchar>& parent, vector<uchar>& labels ) {
int ConnectedComponent::disjointFind( int a, vector<int>& parent, vector<int>& labels ) {
while( parent[a] > 0 )
a = parent[a];
if( labels[a] == 0 )
Expand All @@ -129,8 +137,8 @@ uchar ConnectedComponent::disjointFind( uchar a, vector<uchar>& parent, vector<u
*
* returns a vector of that contains unique neighbor labels
*/
vector<uchar> ConnectedComponent::getNeighbors( uchar * curr_ptr, uchar * prev_ptr, int x, int y, int cols ) {
vector<uchar> neighbors;
vector<int> ConnectedComponent::getNeighbors( int * curr_ptr, int * prev_ptr, int x, int y, int cols ) {
vector<int> neighbors;

/* Actually we only consider pixel 1, 2, 3, and 4 */
/* At this point of time, the logic hasn't traversed thru 5, 6, 7, 8 */
Expand All @@ -151,7 +159,7 @@ vector<uchar> ConnectedComponent::getNeighbors( uchar * curr_ptr, uchar * prev_p

/* Reduce to unique labels */
/* This is because I'm not using set (it doesn't have random element access) */
vector<uchar> result;
vector<int> result;
if( !neighbors.empty() ) {
std::sort( neighbors.begin(), neighbors.end() );
std::unique_copy( neighbors.begin(), neighbors.end(), std::back_inserter( result ) );
Expand Down
17 changes: 9 additions & 8 deletions ConnectedComponent/ConnectedComponent/ConnectedComponent.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,27 +14,28 @@


/**
* Connected component labelling using 8-connected neighbors, based on
* Connected component labeling using 8-connected neighbors, based on
* http://en.wikipedia.org/wiki/Connected-component_labeling
*
* with disjoint union and find functions adapted from :
* https://courses.cs.washington.edu/courses/cse576/02au/homework/hw3/ConnectComponent.java
*/
class ConnectedComponent {
public:
ConnectedComponent();
ConnectedComponent( int max_component = 1000 );
virtual ~ConnectedComponent();
cv::Mat apply( const cv::Mat& image );
int getComponentsCount();

protected:
void disjointUnion( uchar a, uchar b, std::vector<uchar>& parent );
uchar disjointFind( uchar a, std::vector<uchar>& parent, std::vector<uchar>& labels );
std::vector<uchar> getNeighbors( uchar * curr_ptr, uchar * prev_ptr, int x, int y, int cols );

void disjointUnion( int a, int b, std::vector<int>& parent );
int disjointFind( int a, std::vector<int>& parent, std::vector<int>& labels );
std::vector<int> getNeighbors( int * curr_ptr, int * prev_ptr, int x, int y, int cols );
private:
uchar nextLabel;
std::vector<uchar> labels;
int maxComponent;
int nextLabel;
std::vector<int> labels;
};

#endif /* defined(__RobustTextDetection__ConnectedComponent__) */
38 changes: 21 additions & 17 deletions ConnectedComponent/ConnectedComponent/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,17 +40,20 @@ void test1() {

/* Apply connected component labelling */
ConnectedComponent conn_comp;
Mat label = conn_comp.apply( image );
cvtColor( label, label, CV_GRAY2BGR );
Mat labels = conn_comp.apply( image );

/* Recolor the labels */
for( int y = 0; y < label.rows; y++ ) {
Vec3b * ptr = label.ptr<Vec3b>(y);
for( int x = 0; x < label.cols; x++ )
ptr[x] = color_map[ptr[x][0] % color_map.size()];
Mat colored( image.size(), CV_8UC3, Scalar::all(0) );
for( int y = 0; y < labels.rows; y++ ) {
Vec3b * ptr = colored.ptr<Vec3b>(y);
int * label_ptr = labels.ptr<int>(y);

for( int x = 0; x < labels.cols; x++ )
ptr[x] = color_map[ label_ptr[x] % color_map.size() ];
}

resize( label, label, Size(), 30.0, 30.0, CV_INTER_NN );

resize( colored, colored, Size(), 30.0, 30.0, CV_INTER_NN );

/* Convert our original image into appropriate size and type */
image = image * 255;
Expand All @@ -60,7 +63,7 @@ void test1() {
/* Append the two images together side by side */
Mat appended( image.rows, image.cols * 2, CV_8UC3 );
image.copyTo( Mat( appended, Rect(0, 0, image.cols, image.rows) ) );
label.copyTo( Mat( appended, Rect(image.cols, 0, image.cols, image.rows) ) );
colored.copyTo( Mat( appended, Rect(image.cols, 0, image.cols, image.rows) ) );

imshow("", appended);
while( waitKey(10) != 'q' );
Expand All @@ -74,22 +77,23 @@ void test2() {
threshold( image, binary, 200.0, 1.0, CV_THRESH_BINARY_INV );

ConnectedComponent conn_comp;
Mat label = conn_comp.apply( binary );

cvtColor( label, label, CV_GRAY2BGR );

Mat labels = conn_comp.apply( binary );

/* Recolor the labels */
for( int y = 0; y < label.rows; y++ ) {
Vec3b * ptr = label.ptr<Vec3b>(y);
for( int x = 0; x < label.cols; x++ )
ptr[x] = color_map[ptr[x][0] % color_map.size()];
Mat colored( image.size(), CV_8UC3, Scalar::all(0) );
for( int y = 0; y < labels.rows; y++ ) {
Vec3b * ptr = colored.ptr<Vec3b>(y);
int * label_ptr = labels.ptr<int>(y);

for( int x = 0; x < labels.cols; x++ )
ptr[x] = color_map[ label_ptr[x] % color_map.size() ];
}

cvtColor( image, image, CV_GRAY2BGR );
/* Append the two images together side by side */
Mat appended( image.rows, image.cols * 2, CV_8UC3 );
image.copyTo( Mat( appended, Rect(0, 0, image.cols, image.rows) ) );
label.copyTo( Mat( appended, Rect(image.cols, 0, image.cols, image.rows) ) );
colored.copyTo( Mat( appended, Rect(image.cols, 0, image.cols, image.rows) ) );

imshow( "", appended );
while( waitKey(10) != 'q' );
Expand Down

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