// i am using this code to convert a 24 bit color imaget 8 bit grey image
but i ma getting output image like if you divide image into 3 parts
last part is displaying first then next tw parts
i unable to understand whyit happens
any one help me

long getImageInfo(FILE*, long, int);
void copyImageInfo(FILE* inputFile, FILE* outputFile);
void createColorTable(FILE* inputFile, FILE* outputFile);

/*--STRUCTURES---*/
typedef struct {int rows; int cols; unsigned char* data;} sImage;

int main(int argc, char* argv[])
{
FILE *bmpInput, *rasterOutput, *bmpOutput, *grayBmpInput;
sImage originalImage;
unsigned char someChar;
unsigned char *pChar;
unsigned long someLong;
unsigned long *pLong;
long fileSize;
int vectorSize, nColors;
int r, c, i;
int redValue, greenValue, blueValue, grayValue;

/*---INITIALIZE POINTER----*/
someChar = '0';
pChar = &someChar;

someLong = '0';
pLong = &someLong;

/*if(argc < 2)
{
printf("Usage: %s bmpInput.bmp\n", argv[0]);
exit(0);
}*/



/*--DECLARE INPUT FILES--*/
bmpInput = fopen("color.bmp", "rb");
fseek(bmpInput, 0L, SEEK_END);
grayBmpInput = fopen("p1.bmp", "rb");
fseek(grayBmpInput, 0L, SEEK_END);

/*--DECLARE OUTPUT FILES--*/
rasterOutput = fopen("data24.txt", "w");
bmpOutput = fopen("gray24.bmp", "wb");

/*--GET INPUT BMP DATA--*/
originalImage.cols = (int)getImageInfo(bmpInput, 18, 4);
originalImage.rows = (int)getImageInfo(bmpInput, 22, 4);
fileSize = getImageInfo(bmpInput, 2, 4);
nColors = getImageInfo(bmpInput, 46, 4);

/*--PRINT DATA TO SCREEN--*/
printf("Width: %d\n", originalImage.cols);
printf("Height: %d\n", originalImage.rows);
printf("File size: %ld\n", fileSize);
printf("Bits/pixel: %d\n", getImageInfo(bmpInput, 28, 2));
printf("No. colors: %d\n\n", nColors);

/*----------------

TRIED TO COPY COLOR TABLE OF ANOTHER
GRAYSCALE IMAGE???

----------------*/
copyImageInfo(bmpInput, bmpOutput);

/*--EDIT FILE SIZE TO CONFORM TO 8 BIT BMP--*/
fseek(bmpOutput, 2, SEEK_SET);
*pLong = (unsigned long)(54 + 4*256 + (originalImage.cols * originalImage.rows));
fwrite(pLong, sizeof(unsigned long), 1, bmpOutput);
printf("File size: %ld\n", (long)getImageInfo(bmpOutput, 2, 4));

/*--CHANGE BIT DEPTH FROM 24 TO 8--*/
fseek(bmpOutput, 28, SEEK_SET);
*pLong = (unsigned long)(8);
fwrite(pLong, sizeof(unsigned long), 1, bmpOutput);
printf("Bits/pixel: %d\n", (int)getImageInfo(bmpOutput, 28, 2));

/*--CHANGE #COLORS FROM 16M TO 256--*/
fseek(bmpOutput, 46, SEEK_SET);
*pLong = (unsigned long)(256);
fwrite(pLong, sizeof(unsigned long), 1, bmpOutput);
printf("No. colors: %d\n", (int)getImageInfo(bmpOutput, 46, 4));

createColorTable(grayBmpInput, bmpOutput);

/*--FOR 24-BIT BMP, THERE IS NO COLOR TABLE--*/
fseek(bmpInput, 54, SEEK_SET);
fseek(bmpOutput, (54 + 4*256), SEEK_SET);
long value=ftell(bmpOutput);
printf("current position: %ld\n", (long)value);
/*----READ RASTER DATA----*/
for(r=0; r<=originalImage.rows-1; r++)
{
for(c=0; c<=originalImage.cols-1; c++)
{
/*--READ FIRST BYTE TO GET BLUE VALUE--*/
fread(pChar, sizeof(char), 1, bmpInput);
blueValue = *pChar;

/*--READ NEXT BYTE TO GET GREEN VALUE--*/
fread(pChar, sizeof(char), 1, bmpInput);
greenValue = *pChar;

/*--READ NEXT BYTE TO GET RED VALUE--*/
fread(pChar, sizeof(char), 1, bmpInput);
redValue = *pChar;

/*--USE FORMULA TO CONVERT RGB VALUE TO GRAYSCALE--*/
grayValue = (int)(0.299*redValue + 0.587*greenValue + 0.114*blueValue);

/*--PRINT TO TEXT FILE--*/
fprintf(rasterOutput, "(%d %d) = \tRed \t%d", r, c, redValue);
fprintf(rasterOutput, "\tGreen \t%d \tBlue \t%d \tGray \t%d\n", greenValue, blueValue, grayValue);

/*--WRITE TO NEW BMP FILE--*/
*pChar = grayValue;
fwrite(pChar, sizeof(char), 1, bmpOutput);
}
}

fclose(bmpInput);
fclose(rasterOutput);
fclose(bmpOutput);
fclose(grayBmpInput);

return 0;




//printf("Hello World!\n");
//return 0;
}

long getImageInfo(FILE* inputFile, long offset, int numberOfChars)
{
unsigned char *ptrC;
long value=0L;
int i;
unsigned char dummy;

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);
}

/*---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 createColorTable(FILE* inputFile, FILE* outputFile)
{
unsigned char *ptrC;
unsigned char dummy;
int i;

dummy = '0';
ptrC = &dummy;

fseek(inputFile, 54L, SEEK_SET);
fseek(outputFile, 54L, SEEK_SET);

for(i=1; i<=4*256; i++)
{
fread(ptrC, sizeof(char), 1, inputFile);
fwrite(ptrC, sizeof(char), 1, outputFile);
}

}