Zhang-Suen thinning algorithm: Difference between revisions

=={{header|C}}==

Input and out images written from and to files. Format of input file is :

<Rows> <Columns>

<Blank pixel character> <Image Pixel character>

<Image of specified rows and columns made up of the two pixel types specified in the second line.>

The images before and after thinning are also printed on the console.

<lang C>

/*Abhishek Ghosh, 24th September 2017*/

#include<stdlib.h>

#include<stdio.h>

char** imageMatrix;

char blankPixel,imagePixel;

typedef struct{

int row,col;

}pixel;

int getBlackNeighbours(int row,int col){

int i,j,sum = 0;

for(i=-1;i<=1;i++){

for(j=-1;j<=1;j++){

if(i!=0 && j!=0)

sum+= (imageMatrix[row+i][col+i]==imagePixel);

}

}

return sum;

}

int getBWTransitions(int row,int col){

return ((imageMatrix[row-1][col]==blankPixel && imageMatrix[row-1][col+1]==imagePixel)

+(imageMatrix[row-1][col+1]==blankPixel && imageMatrix[row][col+1]==imagePixel)

+(imageMatrix[row][col+1]==blankPixel && imageMatrix[row+1][col+1]==imagePixel)

+(imageMatrix[row+1][col+1]==blankPixel && imageMatrix[row+1][col]==imagePixel)

+(imageMatrix[row+1][col]==blankPixel && imageMatrix[row+1][col-1]==imagePixel)

+(imageMatrix[row+1][col-1]==blankPixel && imageMatrix[row][col-1]==imagePixel)

+(imageMatrix[row][col-1]==blankPixel && imageMatrix[row-1][col-1]==imagePixel)

+(imageMatrix[row-1][col-1]==blankPixel && imageMatrix[row-1][col]==imagePixel));

}

int zhangSuenTest1(int row,int col){

int neighbours = getBlackNeighbours(row,col);

return ((neighbours>=2 && neighbours<=6)

&& (getBWTransitions(row,col)==1)

&& (imageMatrix[row-1][col]==blankPixel||imageMatrix[row][col+1]==blankPixel||imageMatrix[row+1][col]==blankPixel)

&& (imageMatrix[row][col+1]==blankPixel||imageMatrix[row+1][col]==blankPixel||imageMatrix[row][col-1]==blankPixel));

}

int zhangSuenTest2(int row,int col){

int neighbours = getBlackNeighbours(row,col);

return ((neighbours>=2 && neighbours<=6)

&& (getBWTransitions(row,col)==1)

&& (imageMatrix[row-1][col]==blankPixel||imageMatrix[row][col+1]==blankPixel||imageMatrix[row][col-1]==blankPixel)

&& (imageMatrix[row-1][col]==blankPixel||imageMatrix[row+1][col]==blankPixel||imageMatrix[row][col+1]==blankPixel));

}

void zhangSuen(char* inputFile, char* outputFile){

int startRow = 1,startCol = 1,endRow,endCol,i,j,count,rows,cols,processed;

pixel* markers;

FILE* inputP = fopen(inputFile,"r");

fscanf(inputP,"%d%d",&rows,&cols);

fscanf(inputP,"%d%d",&blankPixel,&imagePixel);

blankPixel<=9?blankPixel+='0':blankPixel;

imagePixel<=9?imagePixel+='0':imagePixel;

printf("\nPrinting original image :\n");

imageMatrix = (char**)malloc(rows*sizeof(char*));

for(i=0;i<rows;i++){

imageMatrix[i] = (char*)malloc((cols+1)*sizeof(char));

fscanf(inputP,"%s\n",imageMatrix[i]);

printf("\n%s",imageMatrix[i]);

}

//fclose(inputP);

endRow = rows-2;

endCol = cols-2;

do{

markers = (pixel*)malloc((endRow-startRow+1)*(endCol-startCol+1)*sizeof(pixel));

count = 0;

for(i=startRow;i<=endRow;i++){

for(j=startCol;j<=endCol;j++){

if(imageMatrix[i][j]==imagePixel && zhangSuenTest1(i,j)==1){

markers[count].row = i;

markers[count].col = j;

count++;

}

}

}

processed = (count>0);

for(i=0;i<count;i++){

imageMatrix[markers[i].row][markers[i].col] = blankPixel;

}

free(markers);

markers = (pixel*)malloc((endRow-startRow+1)*(endCol-startCol+1)*sizeof(pixel));

count = 0;

for(i=startRow;i<=endRow;i++){

for(j=startCol;j<=endCol;j++){

if(imageMatrix[i][j]==imagePixel && zhangSuenTest2(i,j)==1){

markers[count].row = i;

markers[count].col = j;

count++;

}

}

}

if(processed==0)

processed = (count>0);

for(i=0;i<count;i++){

imageMatrix[markers[i].row][markers[i].col] = blankPixel;

}

free(markers);

}while(processed==1);

FILE* outputP = fopen(outputFile,"w");

printf("\n\n\nPrinting image after applying Zhang Suen Thinning Algorithm : \n\n\n");

for(i=0;i<rows;i++){

for(j=0;j<cols;j++){

printf("%c",imageMatrix[i][j]);

fprintf(outputP,"%c",imageMatrix[i][j]);

}

printf("\n");

fprintf(outputP,"\n");

}

fclose(outputP);

printf("\nImage also written to : %s",outputFile);

}

int main()

{

char inputFile[100],outputFile[100];

printf("Enter full path of input image file : ");

scanf("%s",inputFile);

printf("Enter full path of output image file : ");

scanf("%s",outputFile);

zhangSuen(inputFile,outputFile);

return 0;

}

</lang>

Contents of input file : zhImage.txt

<pre>

10 32

0 1

00000000000000000000000000000000

01111111110000000111111110000000

01110001111000001111001111000000

01110000111000001110000111000000

01110001111000001110000000000000

01111111110000001110000000000000

01110111100000001110000111000000

01110011110011101111001111011100

01110001111011100111111110011100

00000000000000000000000000000000

</pre>

Console interaction :

<pre>

Enter full path of input image file : zhImage.txt

Enter full path of output image file : out.txt

Printing original image :

00000000000000000000000000000000

01111111110000000111111110000000

01110001111000001111001111000000

01110000111000001110000111000000

01110001111000001110000000000000

01111111110000001110000000000000

01110111100000001110000111000000

01110011110011101111001111011100

01110001111011100111111110011100

00000000000000000000000000000000

Printing image after applying Zhang Suen Thinning Algorithm :

00000000000000000000000000000000

00111111100000000011111100000000

00100000100000000110000000000000

01000000100000000100000000000000

01000000100000001000000000000000

01111111100000001000000000000000

01000001000000000100000011000000

01000001000001100110000110001100

01000000000010000001111000010000

00000000000000000000000000000000

Image also written to : out.txt

</pre>

Contents of out.txt :

<pre>

00000000000000000000000000000000

00111111100000000011111100000000

00100000100000000110000000000000

01000000100000000100000000000000

01000000100000001000000000000000

01111111100000001000000000000000

01000001000000000100000011000000

01000001000001100110000110001100

01000000000010000001111000010000

00000000000000000000000000000000

</pre>