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active_contour.c
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active_contour.c
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/*
* Author: Aditya Bettadapura
*
* This program reads an image and takes contour points from a text file.
* Using an iterative process, it draws the controur around the desired segment.
*
*/
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#define SQUARE(x) ((x)*(x))
void DrawPlus(unsigned char initialContour[], int colnum, int rownum, int totalCols, int colour)
{
for (int y = rownum-3; y<=rownum+3; y++)
{
initialContour[(y*totalCols)+colnum] = colour;
}
for (int x = colnum-3; x<=colnum+3; x++)
{
initialContour[(rownum*totalCols)+x] = colour;
}
}
double CalculateCellDistance(double distanceImage[], int curCol, int curRow, int nextCol, int nextRow, int inputCols)
{
int mean = 0;
for (int y = -3; y <=3; y++)
{
for (int x = -3; x <=3; x++)
{
distanceImage[(curRow+y)*inputCols+curCol+x] = SQUARE(nextCol - curCol-x) + SQUARE(nextRow - curRow-y);
mean+= sqrt(distanceImage[(curRow+y)*inputCols+curCol+x]);
}
}
return (mean/49);
}
void CalculateCellVariance(double varianceImage[], double distanceImage[], double variance, int curCol, int curRow, int nextCol, int nextRow, int inputCols)
{
int mean = 0;
for (int y = -3; y <=3; y++)
{
for (int x = -3; x <=3; x++)
{
varianceImage[(curRow+y)*inputCols+curCol+x] = SQUARE(sqrt(distanceImage[(curRow+y)*inputCols+curCol+x]) - variance);
}
}
}
void Normalize(double input[], int inputCols, int inputRows, int curCol, int curRow, double output[], int level)
{
double minGrad = input[(curRow*inputCols)+curCol];
double maxGrad = input[(curRow*inputCols)+curCol];
for (int y = -3; y <=3; y++)
{
for (int x = -3; x <=3; x++)
{
if (input[(curRow+y)*inputCols+curCol+x] > maxGrad)
{
maxGrad = input[(curRow+y)*inputCols+curCol+x];
}
else if (input[(curRow+y)*inputCols+curCol+x] < minGrad)
{
minGrad = input[(curRow+y)*inputCols+curCol+x];
}
}
}
for (int y = -3; y <=3; y++)
{
for (int x = -3; x <=3; x++)
{
output[(curRow+y)*inputCols+curCol+x] = (input[(curRow+y)*inputCols+curCol+x] - minGrad)*level/(maxGrad-minGrad);
}
}
}
void NormalizeGray(double input[], int inputCols, int inputRows, unsigned char output[], int level)
{
double min = 0;
double max = 0;
for (int i = 0; i < inputCols*inputRows; i++)
{
if (input[i] > max)
{
max = input[i];
}
else if (input[i] < min)
{
min = input[i];
}
}
for (int i = 0; i < inputCols*inputRows; i++)
{
output[i] = (input[i] - min)*level/(max-min);
}
}
void main(int argc, char *argv[])
{
FILE *fptr;
char *inputHeader;
int inputCols, inputRows, inputBytes;
char Header_1[320];
unsigned char *inputImage, *initialContour;
int initCol[42], initRow[42];
int index = 0;
int contourSqrDist[42];
double mean = 0;
double variance[42];
unsigned char *normalGrad, *normalGrad_x, *normalGrad_y;
double *gradXImage, *gradYImage, *grad;
int sumX, sumY;
int r,c,r2,c2;
double *energyImage;
unsigned char *finalContour;
int newPosition;
double cellAverage[42];
double *varianceImage, *distanceImage;
double *normalVariance, *normalDistance, *normalSobel;
printf("Initialization done!\n");
if ((fptr=fopen("hawk.ppm","r"))==NULL)
{
printf("Unable to open input file for reading\n");
exit(0);
}
if ((fptr=fopen("hawk_init.txt","r"))==NULL)
{
printf("Unable to open contour table for reading\n");
exit(0);
}
printf("Input Check done!\n");
//Open and load input image
fptr = fopen("hawk.ppm", "r");
fscanf(fptr,"%s %d %d %d",&inputHeader, &inputCols, &inputRows, &inputBytes);
Header_1[0]=fgetc(fptr); /* read white-space character that separates header */
inputImage = (unsigned char*)calloc(inputCols*inputRows,sizeof(unsigned char));
fread(inputImage, 1, inputCols*inputRows, fptr);
fclose(fptr);
printf("Input file opened!\n");
//Open and load initial contour points
fptr = fopen("hawk_init.txt","r");
while(fscanf(fptr,"%d %d\n", &initCol[index], &initRow[index]) != EOF)
{
index++;
}
fclose(fptr);
for (int i = 0; i < 42; i++)
{
printf("%d. %d %d \n",i+1, initCol[i], initRow[i]);
}
printf("Initial contour points loaded!\n");
//Copy input image into initialcontour
initialContour = (unsigned char*)calloc(inputCols*inputRows, sizeof(unsigned char));
for (int i = 0; i < inputCols*inputRows; i++)
{
initialContour[i] = inputImage[i];
}
//Draw plus at contour points
for (int i = 0; i < 42; i++)
{
DrawPlus(initialContour, initCol[i], initRow[i], inputCols, 0);
}
//Write out initial contour image
fptr=fopen("initial_contour.ppm","w");
fprintf(fptr,"P5 %d %d 255\n",inputCols,inputRows);
fwrite(initialContour,inputCols*inputRows,1,fptr);
fclose(fptr);
//Allocate memory to all images
distanceImage = (double*)calloc(inputCols*inputRows, sizeof(double));
gradXImage = (double*)calloc(inputCols*inputRows, sizeof(double));
gradYImage = (double*)calloc(inputCols*inputRows, sizeof(double));
grad = (double*)calloc(inputCols*inputRows, sizeof(double));
energyImage = (double*)calloc(inputCols*inputRows, sizeof(double));
finalContour = (unsigned char*)calloc(inputCols*inputRows, sizeof(unsigned char));
normalGrad = (unsigned char*)calloc(inputCols*inputRows, sizeof(unsigned char));
normalGrad_x = (unsigned char*)calloc(inputCols*inputRows, sizeof(unsigned char));
normalGrad_y = (unsigned char*)calloc(inputCols*inputRows, sizeof(unsigned char));
varianceImage = (double*)calloc(inputCols*inputRows, sizeof(double));
normalVariance = (double*)calloc(inputCols*inputRows, sizeof(double));
normalDistance = (double*)calloc(inputCols*inputRows, sizeof(double));
normalSobel = (double*)calloc(inputCols*inputRows, sizeof(double));
//Sobel filter kernels of order 3x3
int sobelX[9] = {1, 0, -1, 2, 0, -2, 1, 0, -1};
int sobelY[9] = {1, 2, 1, 0, 0, 0, -1, -2, -1};
//Compute external energy term
for (r = 0; r < inputRows; r++)
{
for (c = 0; c < inputCols; c++)
{
sumX = 0;
sumY = 0;
for (r2=-1; r2<=1; r2++)
for (c2=-1; c2<=1; c2++)
{
sumX += inputImage[(r+r2)*inputCols+(c+c2)]*sobelX[(r2+1)*3+c2+1];
sumY += inputImage[(r+r2)*inputCols+(c+c2)]*sobelY[(r2+1)*3+c2+1];
}
gradXImage[(r*inputCols)+c]=sumX;
gradYImage[(r*inputCols)+c]=sumY;
grad[(r*inputCols)+c] = (SQUARE(sumX) + SQUARE(sumY));
}
}
NormalizeGray(gradXImage, inputCols, inputRows, normalGrad_x, 255);
NormalizeGray(gradYImage, inputCols, inputRows, normalGrad_y, 255);
NormalizeGray(grad, inputCols, inputRows, normalGrad, 255);
//Calculate Internal energies for 'n' iterations
int iteration = 10;
while(iteration>0)
{
for (int i = 0; i < 42; i++)
{
int next_col = (i+1)%42;
int next_row = (i+1)%42;
//Interal energy 1
cellAverage[i] = CalculateCellDistance(distanceImage, initCol[i], initRow[i], initCol[next_col], initRow[next_row], inputCols);
//Interal energy 2
CalculateCellVariance(varianceImage, distanceImage, cellAverage[i], initCol[i], initRow[i], initCol[next_col], initRow[next_row], inputCols);
}
//Normalize the energies to 0-1 level
for (int i = 0; i < 42; i++)
{
Normalize(varianceImage, inputCols, inputRows, initCol[i], initRow[i], normalVariance,1);
Normalize(distanceImage, inputCols, inputRows, initCol[i], initRow[i], normalDistance,1);
Normalize(grad, inputCols, inputRows, initCol[i], initRow[i], normalSobel,1);
}
for (int i = 0; i < inputCols*inputRows; i++)
{
energyImage[i] = (normalDistance[i] + normalVariance[i] - normalSobel[i])/3;
finalContour[i] = inputImage[i];
}
//Move contour point to position of minimum energy
for (int i = 0; i < 42; i++)
{
int curRow = initRow[i];
int curCol = initCol[i];
int minEnergy = energyImage[curRow*inputCols+curCol];
int newCol, newRow;
for (int y = -3; y <=3; y++)
{
for (int x = -3; x <=3; x++)
{
if (energyImage[(curRow+y)*inputCols+curCol+x] < minEnergy)
{
newCol = curCol+x;
newRow = curRow+y;
}
}
}
DrawPlus(finalContour, newCol, newRow, inputCols, 0);
initRow[i] = newRow;
initCol[i] = newCol;
}
iteration--;
printf("iterations = %d\n",iteration);
}
//Print final positions
fptr=fopen("output.txt","w");
for (int i = 0; i < 42; i++)
{
fprintf(fptr, "%d %d\n", initCol[i], initRow[i]);
printf("%d %d\n", initCol[i], initRow[i]);
}
fclose(fptr);
//Write out the output images
fptr=fopen("normalized_gradient_x.ppm","w");
fprintf(fptr,"P5 %d %d 255\n",inputCols,inputRows);
fwrite(normalGrad_x,inputCols*inputRows,1,fptr);
fclose(fptr);
fptr=fopen("normalized_gradient_y.ppm","w");
fprintf(fptr,"P5 %d %d 255\n",inputCols,inputRows);
fwrite(normalGrad_y,inputCols*inputRows,1,fptr);
fclose(fptr);
fptr=fopen("normalized_gradient.ppm","w");
fprintf(fptr,"P5 %d %d 255\n",inputCols,inputRows);
fwrite(normalGrad,inputCols*inputRows,1,fptr);
fclose(fptr);
fptr=fopen("final_contour.ppm","w");
fprintf(fptr,"P5 %d %d 255\n",inputCols,inputRows);
fwrite(finalContour,inputCols*inputRows,1,fptr);
fclose(fptr);
//Free allocated memory
free(initialContour);
free(distanceImage);
free(gradXImage);
free(gradYImage);
free(grad);
free(energyImage);
free(finalContour);
free(normalGrad);
free(normalGrad_x);
free(normalGrad_y);
free(varianceImage);
free(normalVariance);
free(normalDistance);
free(normalSobel);
}