save bmp file using c on linux - c

Question

I tried to open bmp file and save it using c code. My code worked well on window compiler(visual studio) but it didn't work on linux using gcc. Even though the format of final output is bmp, it shows like empty file(white). I'm a beginner for using linux and c programming so I'm not sure what's wrong with this happening!
I compiled it using gcc: gcc bmp.c -o bmp.
the code below is what I used.
#define _CRT_SECURE_NO_WARNINGS
#include<stdlib.h>
#include<string.h>
#include<stdio.h>
#define WIDTHBYTES(bits) (((bits)+31)/32*4)
#pragma pack(push, 1)
typedef unsigned short WORD;
typedef unsigned long DWORD;
typedef long LONG;
typedef struct tagBITMAPFILEHEADER {
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} BITMAPFILEHEADER;
typedef struct tagBITMAPINFOHEADER {
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} BITMAPINFOHEADER;
typedef struct tagRGBQUAD {
unsigned char rgbBlue;
unsigned char rgbGreen;
unsigned char rgbRed;
unsigned char rgbReserved;
} RGBQUAD;
typedef struct tagBITMAPINFO {
BITMAPINFOHEADER bmiHeader;
RGBQUAD bmiColors[1];
} BITMAPINFO;
int main(int argc, char* argv[]){
FILE *infile;
FILE *outfile;
BITMAPFILEHEADER hf;
BITMAPINFOHEADER hInfo;
RGBQUAD hRGBpal[256];
unsigned char *lpImg;
int i, j, pos, rwsize;
int nBitCount = 1;
infile = fopen("image.bmp", "rb");
if (infile == NULL)
{
printf("no image");
return 1;
}
fread(&hf, sizeof(BITMAPFILEHEADER), 1, infile);
if (hf.bfType != 0x4d42)
{
printf("ERROR\n");
fclose(infile);
exit(1);
}
fread(&hInfo, sizeof(BITMAPINFOHEADER), 1, infile);
if (hInfo.biBitCount == 8 || hInfo.biBitCount == 16 ||
hInfo.biBitCount == 24 || hInfo.biBitCount == 32)
{
nBitCount = hInfo.biBitCount / 8;
if (hInfo.biBitCount == 8)
{
pos = hf.bfOffBits - hf.bfSize - hInfo.biSize;
if (pos > 0)
{
fread((unsigned char *)hRGBpal, sizeof(unsigned char), pos, infile);
}
}
lpImg = (unsigned char*)malloc(hInfo.biSizeImage);
fseek(infile, hf.bfOffBits, SEEK_SET);
fread(lpImg, sizeof(unsigned char), hInfo.biSizeImage, infile);
fclose(infile);
}
rwsize = WIDTHBYTES(hInfo.biBitCount*hInfo.biWidth);
for (i = 0; i < hInfo.biHeight; i++)
{
for (j = 0; j < hInfo.biWidth; j++)
{
lpImg[i*rwsize + j];
}
}
outfile = fopen("out.bmp", "wb")
if (hInfo.biBitCount == 8)
{
hf.bfOffBits = sizeof(BITMAPFILEHEADER)
+ sizeof(BITMAPINFOHEADER) + sizeof(hRGBpal);
}
fwrite(&hf, sizeof(char), sizeof(BITMAPFILEHEADER), outfile);
fwrite(&hInfo, sizeof(char), sizeof(BITMAPINFOHEADER), outfile);
if (hInfo.biBitCount == 8)
{
fwrite(hRGBpal, sizeof(RGBQUAD), 256, outfile);
}
fwrite(lpImg, sizeof(unsigned char), hInfo.biSizeImage, outfile);
fclose(outfile);
if (lpImg)
free(lpImg);
printf("DONE!");}

Answer 1

This probably goes wrong here:
typedef unsigned short WORD;
typedef unsigned long DWORD;
typedef long LONG;
If you're on 64bit Linux, long has 64 bits. On 64bit Windows, it has only 32bits. For portable code, use fixed-size integers:
typedef uint16_t WORD;
typedef uint32_t DWORD;
typedef int32_t LONG;
On a further note, there's no need to introduce these ugly (my opinion here) winapi typedefs at all. A (sloppy) version of the bitmap file header I'm using (still relying on the "packed struct" feature and merging both structs into one) looks like this:
#pragma pack(push)
#pragma pack(1)
struct bmphdr
{
uint16_t bfType;
uint32_t bfSize;
uint32_t bfReserved;
uint32_t bfOffBits;
uint32_t biSize;
uint32_t biWidth;
int32_t biHeight;
uint16_t biPlanes;
uint16_t biBitCount;
uint32_t biCompression;
uint32_t biSizeImage;
int32_t biXPelsPerMeter;
int32_t biYPelsPerMeter;
uint32_t biClrUsed;
uint32_t biClrImportant;
};
#pragma pack(pop)