Incomplete image is written using fwrite() - c++

Question

I was writing a code to read and write an image file, but my code works fine except for only one fourth of the image is written when using fwrite()...Please help me find out where i've mistaken.Thanks in advance.
PS I'm a newbie in this field.
This is my code for the read and write functions.
Please ignore any silly things I might have coded to get the work done.
#include<iostream>
#include <cstdlib>
#include <cstdio>
#define FALSE 0
#define TRUE 1
int c,numberOfCols,numberOfRows,HighVal,totalPx,header;
int** a;
int doneReading = FALSE;
char * string;
unsigned char * image;
//Read Image
int readImage(char **argv){
FILE * pFile;
pFile = fopen (argv[1],"rt");
if (pFile==NULL) perror ("Error opening file");
else {
string = (char *)calloc(256,1);
while (!(doneReading) && !feof (pFile)) {
c=(char)getc (pFile);
switch(c){
case 'P':
c=(char)getc (pFile);
switch(c){
case '1':
header=1;
std::cout<<".pbm white n black";
break;
case '2':
header=2;
std::cout<<".pgm greyscale";
break;
case '3':
header=3;
std::cout<<".ppm rgb";
break;
}
c=(char)getc (pFile);
if(c==0x0A) ungetc(c,pFile) ;
break;
case '#':
fgets(string,256,pFile);
std::cout<<"File you entered is "<<string<<"\n";
break;
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
ungetc(c,pFile);
fscanf(pFile,"%d %d %d",&(numberOfCols),&(numberOfRows),&(HighVal));
doneReading=TRUE;
std::cout<<"Done";
std::cout<<"\nNo. of columns: "<<numberOfCols<<"\nNo. of Columns: "<<numberOfRows<<"\nMaximum Intensity: "<<HighVal<<"\n";
break;
}
totalPx=numberOfCols*numberOfRows*1;
image=(unsigned char *)malloc(totalPx);
fread(image,1,totalPx,pFile);
}
std::cout<<"Image read from "<<argv[1]<<"...\n";
}
return totalPx;
}
//Write Image
void writeImage(char **argv,int pixels){
FILE *fOut;
fOut=fopen(argv[2],"wt");
if (fOut==NULL) perror ("Error opening file");
else {
fprintf(fOut,"P%d \n%d %d \n%d",header,numberOfCols,numberOfRows,HighVal);
fwrite(image,1,pixels,fOut);
std::cout<<"Image Written on "<<argv[2]<<"...";
}
}
int main (int argc,char **argv)
{
int pixels;
pixels = readImage(argv);
writeImage(argv,pixels);
return 0;
}

Answer 1

Your problem appears to be with the value returned from readImage(). It's returning the number of pixels without taking into account the size of a pixel. This line:
totalPx=numberOfCols*numberOfRows*1;
returns the number of pixels, but a pixel can be 1, 2, 4 or more bytes. Assuming your image data is RGBA, then you need to multiply that by 4 in the call to either writeImage() or fwrite().