Writing Bitmap Image to File - c

Question

I'm trying to read in a bitmap image from one file and write it to another just to check that the contents were transferred. However when I run my code, the image doesn't get created into the output file. Instead, whenever I click on the new file it tells me that the file couldn't be opened. Here is what my header file looks like:
//////////////////////////////////////////////////////////////////////
// RGB.h header file for bitmap BMP definitions
// adapted from <WinGDI.h>
///To get DIB header struct. winGDI.h is huge overkill for the needs here
#ifndef RGBH //don't doubly include this stuff, set a flag when first including
#define RGBH
/* structures for defining DIBs //from WinGDI.h */
typedef unsigned short WORD;
typedef unsigned int DWORD;
typedef unsigned long int LONG;
typedef unsigned char BYTE;
typedef struct tagBITMAPFILEHEADER {
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} BITMAPFILEHEADER, *PBITMAPFILEHEADER;
typedef PBITMAPFILEHEADER pbfh;
typedef struct tagBITMAPINFOHEADER {
DWORD biSize; /* used to get to color table */
DWORD biWidth;
DWORD biHeight;
WORD biPlanes;
WORD biBitCount;
} BITMAPINFOHEADER, *PBITMAPINFOHEADER;
typedef BITMAPINFOHEADER pbih;
typedef struct tagRGBTRIPLE { //from WinGDI.h
BYTE b; //rgbtBlue;
BYTE g; //rgbtGreen;
BYTE r; //rgbtRed;
} pix, *ppix;
#define BYTES_PER_PIX sizeof(pix)
const pix RED = {0,0,255};
const pix GREEN = {0,255,0};
const pix BLUE = {255,0,0};
#endif
////////////////////// End of RGB.h header file ////////////////////////////////
And here is the code I have written:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "RGB.h" //header file for Bitmap
BITMAPFILEHEADER *hp; //var pointer to the header file for bitmap
BITMAPINFOHEADER *p; //var pointer to the info file for bitmap
#define SIZE 100
int main(void)
{
FILE *bp, *op; //var for two file streams
char pix[SIZE]; //var for char name of input file
char out[SIZE]; //var for char name of output file
int n; //var to hold different values through out the program
unsigned char *bitmapImage; //var to store image data
printf("Enter bitmap filename: "); //prompts user to enter filename
scanf("%s", pix); //collects filename from user
//open filename in read binary mode
if((bp = fopen(pix, "rb")) == NULL) if ((bp = fopen(pix, "rb")) == NULL)
{
printf("Can't open file %s", bp); //prints if file path wasn't valid
getchar();
exit (1);
}
//malloc memory for file header
hp = (tagBITMAPFILEHEADER*)malloc(sizeof(tagBITMAPFILEHEADER));
//reads the bitmap file header
n = fread(pix, 1,SIZE, bp);
//read bitmap info header
fread(bp, sizeof(tagBITMAPINFOHEADER), 1, bp);
//allocate enough memory for the bitmap image data
p = (tagBITMAPINFOHEADER*) (pix+14);
bitmapImage = (unsigned char*) malloc(p->biSize);
//verify memory allocation
if (!bitmapImage)
{
free(bitmapImage);
fclose(bp);
puts("Memory allocation not allowed");
return NULL;
}
puts("Input File Statistics: \n");
printf("File size: %ld bytes", p->biSize); //prints out total file size
printf("\nWidth x Height = %ld x %ld", p->biWidth, p->biHeight); //prints out dimensions of image
printf("\nBits/pixel = %u\n", p->biBitCount);
printf("\nEnter an output filename for bitmap: "); //prompts user for output file name
scanf("%s", out); //collects pathway from user
//open output file
if((op = fopen(out, "wb")) == NULL)
{
puts("Invalid file");
fclose(op);
exit (2);
}
fclose(op);
return 0;
}
Any advice would be greatly appreciated! Thanks! O. Helm

Answer 1

Sometimes the solution is too easy to see.
Are you using the same "counter" in both for loops? I think that will not work.
Also, in your fread and fwrite, you are probably reading to and writing from the same place. You need to update the pointer of where you are reading to.
The comment for your first fread says "reads the bitmap file header". I am not sure it is doing that correctly.
Check your second fread. It might have a fatal problem. Are you sure you want to read into bp? Perhaps it will help you if you use more meaningful names for your variables.
Do you need to write BITMAPFILEHEADER and BITMAPINFOHEADER out? Check to ensure you are doing that correctly.
Since this is a class assignment, obviously it is best to not give precise help. I hope this helps enough to make progress. If there is anything more than I hope you can find them by looking closely.