读取BMP文件C ++(读取BMP标头出现问题) [英] Reading BMP file C++ (trouble with reading BMP header)

问题描述

我正在尝试使用读取方法编写BMP图像类.我看到了BMP文件的msdn规范，因此我尝试读取标头，然后使用biHeight和biWidth信息读取每个像素的RGB信息.因此，它不读取标头信息，每个标头参数的值为-1.

I am trying to write BMP image class with reading method. I saw msdn specification of BMP files, so I try to read the headers and after, using the biHeight and biWidth information, read RGB info of every pixel. So, it don't read header information, the value of every header parameter is -1.

这里的代码:

#ifndef BMP_IMAGE_H
#define BMP_IMAGE_H

#include <fstream>

using namespace std;


typedef struct
{
    unsigned int    bfType;
    unsigned long   bfSize;
    unsigned int    bfReserved1;
    unsigned int    bfReserved2;
    unsigned long   bfOffBits;
} BitMapFileHeader;

typedef struct
{
    unsigned int    biSize;
    int             biWidth;
    int             biHeight;
    unsigned short  biPlanes;
    unsigned short  biBitCount;
    unsigned int    biCompression;
    unsigned int    biSizeImage;
    int             biXPelsPerMeter;
    int             biYPelsPerMeter;
    unsigned int    biClrUsed;
    unsigned int    biClrImportant;
} BitMapInfoHeader;

typedef struct
{
    int   rgbBlue;
    int   rgbGreen;
    int   rgbRed;
    int   rgbReserved;
} RGBColor;


class BMPImage
{
private:
    unsigned short read_u16();
    unsigned int   read_u32();
    int            read_s32();
public:
    ifstream pFile;
    int imageWidth;
    int imageHeight;
    RGBColor **rgb;
    BMPImage(char* fileName);
    void pixelsInfo();
};

#endif // BMP_IMAGE_H

#include "bmp_image.h"
#include <iostream>
using namespace std;
BMPImage::BMPImage(char* fileName)
{
     ifstream pFile(fileName, ios::in | ios::binary);


     // read the header of file
     BitMapFileHeader header __attribute__((unused));

     header.bfType      = read_u16();
     header.bfSize      = read_u32();
     header.bfReserved1 = read_u16();
     header.bfReserved2 = read_u16();
     header.bfOffBits   = read_u32();

     // read the header of image
     BitMapInfoHeader bmiHeader;

     bmiHeader.biSize          = read_u32();
     bmiHeader.biWidth         = read_s32();
     bmiHeader.biHeight        = read_s32();
     bmiHeader.biPlanes        = read_u16();
     bmiHeader.biBitCount      = read_u16();
     bmiHeader.biCompression   = read_u32();
     bmiHeader.biSizeImage     = read_u32();
     bmiHeader.biXPelsPerMeter = read_s32();
     bmiHeader.biYPelsPerMeter = read_s32();
     bmiHeader.biClrUsed       = read_u32();
     bmiHeader.biClrImportant  = read_u32();

     cout << (int)bmiHeader.biHeight <<"\n";
     RGBColor **rgb = new RGBColor*[bmiHeader.biHeight];
     for (int i = 0; i < bmiHeader.biWidth; i++)
            rgb[i] = new RGBColor[bmiHeader.biHeight];

     for (int i = 0; i < bmiHeader.biWidth; i++) {
         for (int j = 0; j < bmiHeader.biHeight; j++) {
            rgb[i][j].rgbBlue = pFile.get();
            rgb[i][j].rgbGreen = pFile.get();
            rgb[i][j].rgbRed = pFile.get();


         }


         char temp;
         pFile.get(temp);
      }

     imageWidth = bmiHeader.biWidth;
     imageHeight = bmiHeader.biHeight;

     pFile.close();
}

unsigned short BMPImage::read_u16(){
    unsigned char b0, b1;
    b0 = pFile.get();
    b1 = pFile.get();

    return ((b1 << 8) | b0);
}

unsigned int BMPImage::read_u32(){
    unsigned char b0, b1, b2, b3;
    b0 = pFile.get();
    b1 = pFile.get();
    b2 = pFile.get();
    b3 = pFile.get();

    return ((((((b3 << 8) | b2) << 8) | b1) << 8) | b0);
}

int BMPImage::read_s32(){
        unsigned char b0, b1, b2, b3;
        b0 = pFile.get();
        b1 = pFile.get();
        b2 = pFile.get();
        b3 = pFile.get();
        return ((int)(((((b3 << 8) | b2) << 8) | b1) << 8) | b0);

}

void BMPImage::pixelsInfo(){
    for (int i = 0; i < imageWidth; i++) {
            for (int j = 0; j < imageHeight; j++) {
                std::cout << rgb[i][j].rgbRed <<" " << rgb[i][j].rgbGreen << " " << rgb[i][j].rgbBlue << std::endl;
            }
            std::cout << std::endl;
        }
}

P.S.谢谢大家的帮助

P.S. Thank you everybody for help

推荐答案

成员

ifstream pFile;

BMPImage类的

尚未初始化，因此在成员函数中使用它时无效.相反，您是在构造函数中本地定义其他pFile实例.这些可能应该是同一实例.

of class BMPImage is not being initialized, so when you use it in member functions it isn't valid. Instead you are locally defining a different pFile instance in the constructor. These should probably be the same instance.

这篇关于读取BMP文件C ++(读取BMP标头出现问题)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！