[英]reading a .bmp file in c++
我正在嘗試加載一個bmp文件,以便在opengl中重用它。 我已經通過谷歌找到了一些關於如何加載bmp文件的代碼。 我接受了這段代碼並在我的項目中添加了一個類Bitmap。 該類遠沒有完成,但已經讀取文件頭錯了。 在讀取INFOHEADER和FILEHEADER的字節后,我的結構中沒有正確的值。 一些想法?
//
// 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
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);
}
}
標頭需要2字節對齊。
#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
如何讓你的Windows操作系統使用LoadImage
為你加載它。
HBITMAP hbm = LoadImage( NULL, path, 0, 0, LR_LOADFROMFILE|LR_CREATEDIBSECTION);
如果要獲取各個位,請使用GetObject()
查找大小等更多信息和GetDIBits()
。
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