I'm trying to load a bmp file for reusing it in opengl. I've found some code via google on how to load a bmp file. I took this code and put in a class Bitmap in my project. The class is far away from being finished but already the reading of the file headers goes wrong. After reading the bytes for INFOHEADER and FILEHEADER there aren't the right values in my structs. Some ideas?
//
// Bitmap.h
//
#ifndef LaserMaze_Bitmap_h
#define LaserMaze_Bitmap_h
typedef struct /**** BMP file header structure ****/
{
unsigned short bfType; /* Magic number for file */
unsigned int bfSize; /* Size of file */
unsigned short bfReserved1; /* Reserved */
unsigned short bfReserved2; /* ... */
unsigned int bfOffBits; /* Offset to bitmap data */
} BITMAPFILEHEADER;
# define BF_TYPE 0x4D42 /* "MB" */
typedef struct /**** BMP file info structure ****/
{
unsigned int biSize; /* Size of info header */
int biWidth; /* Width of image */
int biHeight; /* Height of image */
unsigned short biPlanes; /* Number of color planes */
unsigned short biBitCount; /* Number of bits per pixel */
unsigned int biCompression; /* Type of compression to use */
unsigned int biSizeImage; /* Size of image data */
int biXPelsPerMeter; /* X pixels per meter */
int biYPelsPerMeter; /* Y pixels per meter */
unsigned int biClrUsed; /* Number of colors used */
unsigned int biClrImportant; /* Number of important colors */
} BITMAPINFOHEADER;
/*
* Constants for the biCompression field...
*/
# define BI_RGB 0 /* No compression - straight BGR data */
# define BI_RLE8 1 /* 8-bit run-length compression */
# define BI_RLE4 2 /* 4-bit run-length compression */
# define BI_BITFIELDS 3 /* RGB bitmap with RGB masks */
typedef struct /**** Colormap entry structure ****/
{
unsigned char rgbBlue; /* Blue value */
unsigned char rgbGreen; /* Green value */
unsigned char rgbRed; /* Red value */
unsigned char rgbReserved; /* Reserved */
} RGBQUAD;
class Bitmap {
public:
Bitmap(const char* filename);
~Bitmap();
RGBQUAD* pixels;
BITMAPFILEHEADER fh;
BITMAPINFOHEADER ih;
private:
};
#endif
the cpp
// Bitmap.cpp
//
#include <iostream>
#include <stdio.h>
#include "Bitmap.h"
Bitmap::Bitmap(const char* filename) {
FILE* file;
file = fopen(filename, "rb");
std::cout << sizeof(BITMAPFILEHEADER) << std::endl;
if(file != NULL) { // file opened
BITMAPFILEHEADER h;
size_t x = fread(&h, sizeof(BITMAPFILEHEADER), 1, file); //reading the FILEHEADER
std::cout << x;
fread(&this->ih, sizeof(BITMAPINFOHEADER), 1, file);
fclose(file);
}
}
Answer
The header needs to be 2 byte aligned.
#pragma pack(2) // Add this
typedef struct
{
unsigned short bfType;
unsigned int bfSize;
unsigned short bfReserved1;
unsigned short bfReserved2;
unsigned int bfOffBits;
} BITMAPFILEHEADER;
#pragma pack() // and this