/*
FILE: edgeSob.c - WORKS!!
AUTH: Bill Green
DESC: 2 3x3 Sobel masks for edge detection
DATE: 07/23/02
REFS: edgeLap.c
*/
#include
#include
#include
#include
/*-------STRUCTURES---------*/
typedef struct {int rows; int cols; unsigned char* data;} sImage;
/*-------PROTOTYPES---------*/
long getImageInfo(FILE*, long, int);
void copyImageInfo(FILE* inputFile, FILE* outputFile);
void copyColorTable(FILE* inputFile, FILE* outputFile, int nColors);
int main(int argc, char* argv[])
{
FILE *bmpInput, *bmpOutput;
sImage originalImage;
sImage edgeImage;
unsigned int X, Y;
int I, J;
long sumX, sumY;
int nColors, SUM;
unsigned long vectorSize;
unsigned long fileSize;
int GX[3][3];
int GY[3][3];
unsigned char *pChar, someChar;
unsigned int row, col;
someChar = '0'; pChar = &someChar;
/* 3x3 GX Sobel mask. Ref: www.cee.hw.ac.uk/hipr/html/sobel.html */
GX[0][0] = -1; GX[0][1] = 0; GX[0][2] = 1;
GX[1][0] = -2; GX[1][1] = 0; GX[1][2] = 2;
GX[2][0] = -1; GX[2][1] = 0; GX[2][2] = 1;
/* 3x3 GY Sobel mask. Ref: www.cee.hw.ac.uk/hipr/html/sobel.html */
GY[0][0] = 1; GY[0][1] = 2; GY[0][2] = 1;
GY[1][0] = 0; GY[1][1] = 0; GY[1][2] = 0;
GY[2][0] = -1; GY[2][1] = -2; GY[2][2] = -1;
if(argc < 2) {
printf("Usage: %s bmpInput.bmp\n", argv[0]);
exit(0);
};
printf("Reading filename %s\n", argv[1]);
/*-------DECLARE INPUT & OUTPUT FILES-------*/
bmpInput = fopen(argv[1], "rb");
bmpOutput = fopen("edgeSob.bmp", "wb");
/*---SET POINTER TO BEGINNING OF FILE----*/
fseek(bmpInput, 0L, SEEK_END);
/*-------GET INPUT BMP DATA--------*/
fileSize = getImageInfo(bmpInput, 2, 4);
originalImage.cols = (int)getImageInfo(bmpInput, 18, 4);
originalImage.rows = (int)getImageInfo(bmpInput, 22, 4);
edgeImage.rows = originalImage.rows;
edgeImage.cols = originalImage.cols;
/*--------PRINT DATA TO SCREEN----------*/
printf("Width: %d\n", originalImage.cols);
printf("Height: %d\n", originalImage.rows);
printf("File size: %lu\n", fileSize);
nColors = (int)getImageInfo(bmpInput, 46, 4);
printf("nColors: %d\n", nColors);
/*------ALLOCATE MEMORY FOR FILES--------*/
vectorSize = fileSize - (14+40+4*nColors);
printf("vectorSize: %lu\n", vectorSize);
edgeImage.data = farmalloc(vectorSize*sizeof(unsigned char));
if(edgeImage.data == NULL) {
printf("Failed to malloc edgeImage.data\n");
exit(0);
}
printf("%lu bytes malloc'ed for edgeImage.data\n", vectorSize);
originalImage.data = farmalloc(vectorSize*sizeof(unsigned char));
if(originalImage.data == NULL) {
printf("Failed to malloc originalImage.data\n");
exit(0);
}
printf("%lu bytes malloc'ed for originalImage.datt\n", vectorSize);
/*------COPY HEADER AND COLOR TABLE---------*/
copyImageInfo(bmpInput, bmpOutput);
copyColorTable(bmpInput, bmpOutput, nColors);
fseek(bmpInput, (14+40+4*nColors), SEEK_SET);
fseek(bmpOutput, (14+40+4*nColors), SEEK_SET);
/* Read input.bmp and store it's raster data into originalImage.data */
for(row=0; row<=originalImage.rows-1; row++) {
for(col=0; col<=originalImage.cols-1; col++) {
fread(pChar, sizeof(char), 1, bmpInput);
*(originalImage.data + row*originalImage.cols + col) = *pChar;
}
}
/*---------------------------------------------------
SOBEL ALGORITHM STARTS HERE
---------------------------------------------------*/
for(Y=0; Y<=(originalImage.rows-1); Y++) {
for(X=0; X<=(originalImage.cols-1); X++) {
sumX = 0;
sumY = 0;
/* image boundaries */
if(Y==0 || Y==originalImage.rows-1)
SUM = 0;
else if(X==0 || X==originalImage.cols-1)
SUM = 0;
/* Convolution starts here */
else {
/*-------X GRADIENT APPROXIMATION------*/
for(I=-1; I<=1; I++) {
for(J=-1; J<=1; J++) {
sumX = sumX + (int)( (*(originalImage.data + X + I + (Y + J)*originalImage.cols)) * GX[I+1][J+1]);
}
}
if(sumX>255) sumX=255;
if(sumX<0) sumX=0;
/*-------Y GRADIENT APPROXIMATION-------*/
for(I=-1; I<=1; I++) {
for(J=-1; J<=1; J++) {
sumY = sumY + (int)( (*(originalImage.data + X + I + (Y + J)*originalImage.cols)) * GY[I+1][J+1]);
}
}
if(sumY>255) sumY=255;
if(sumY<0) sumY=0;
SUM = abs(sumX) + abs(sumY); /*---GRADIENT MAGNITUDE APPROXIMATION (Myler p.218)----*/
}
*(edgeImage.data + X + Y*originalImage.cols) = 255 - (unsigned char)(SUM); /* make edges black and background white */
fwrite( (edgeImage.data + X + Y*originalImage.cols), sizeof(char), 1, bmpOutput);
}
}
printf("See edgeSob.bmp for results\n");
fclose(bmpInput);
fclose(bmpOutput);
farfree(edgeImage.data); /* Finished with edgeImage.data */
farfree(originalImage.data); /* Finished with originalImage.data */
return 0;
}
/*----------GET IMAGE INFO SUBPROGRAM--------------*/
long getImageInfo(FILE* inputFile, long offset, int numberOfChars)
{
unsigned char *ptrC;
long value = 0L;
unsigned char dummy;
int i;
dummy = '0';
ptrC = &dummy;
fseek(inputFile, offset, SEEK_SET);
for(i=1; i<=numberOfChars; i++)
{
fread(ptrC, sizeof(char), 1, inputFile);
/* calculate value based on adding bytes */
value = (long)(value + (*ptrC)*(pow(256, (i-1))));
}
return(value);
} /* end of getImageInfo */
/*-------------COPIES HEADER AND INFO HEADER----------------*/
void copyImageInfo(FILE* inputFile, FILE* outputFile)
{
unsigned char *ptrC;
unsigned char dummy;
int i;
dummy = '0';
ptrC = &dummy;
fseek(inputFile, 0L, SEEK_SET);
fseek(outputFile, 0L, SEEK_SET);
for(i=0; i<=50; i++)
{
fread(ptrC, sizeof(char), 1, inputFile);
fwrite(ptrC, sizeof(char), 1, outputFile);
}
}
/*----------------COPIES COLOR TABLE-----------------------------*/
void copyColorTable(FILE* inputFile, FILE* outputFile, int nColors)
{
unsigned char *ptrC;
unsigned char dummy;
int i;
dummy = '0';
ptrC = &dummy;
fseek(inputFile, 54L, SEEK_SET);
fseek(outputFile, 54L, SEEK_SET);
for(i=0; i<=(4*nColors); i++) /* there are (4*nColors) bytesin color table */
{
fread(ptrC, sizeof(char), 1, inputFile);
fwrite(ptrC, sizeof(char), 1, outputFile);
}
}
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