我仍然是 C++ 的菜鸟，我目前正在尝试创建一个程序，该程序手动将 256 色位图加载到数组并打印出控制台中每个像素的值。在大多数情况下，这些价值观似乎是不正确的。
我的其他输出（例如信息标题内的值）都很好biSizeImage，除了 5 字节。这不应该是 25 字节吗？
出于测试目的，我拍摄了两张 5 x 5 的图像。其中一个是全黑的，另一个是全白的。
我希望黑色的输出类似于：
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
但我得到：
0 0 0 0 0
0 0 0 0 0
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
有了全白的图片，我的结果就更加奇怪了：
4294967295 255 4294967295 255 4294967295
255 4294967295 255 4294967295 255
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
下面你可以看到我当前的代码：
#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
using namespace std;
#pragma pack(push,1)
typedef struct tagBITMAPFILEHEADER {
unsigned short bfType; // Specifies the type of file. This member must be BM. (0x4D42)
unsigned int bfSize; // Specifies the size of the file, in bytes.
short bfReserved1; // Reserved; must be set to zero.
short bfReserved2; // Reserved; must be set to zero.
unsigned int bfOffBits; // Specifies the byte offset from the BITMAPFILEHEADER structure to the actual bitmap data in the file.
} BITMAPFILEHEADER;
typedef struct tagBITMAPINFOHEADER {
unsigned int biSize; // Specifies the number of bytes required by the BITMAPINFOHEADER structure.
int biWidth; // Specifies the width of the bitmap, in pixels.
int biHeight; // Specifies the height of the bitmap, in pixels.
unsigned short biPlanes; // Specifies the number of planes for the target device. This member must be set to 1.
unsigned short biBitCount; // Specifies the number of bits per pixel. This value must be 1,4, 8, or 24.
unsigned int biCompression; // Specifies the type of compression for a compressed bitmap. Itcan be one of the following values: BI_RGB, BI_RLE8, BI_RLE4
unsigned int biSizeImage; // Specifies the size, in bytes, of the image. It is valid to set this member to zero if the bitmap is in the BI_RGB format.
int biXPelsPerMeter; // Specifies the horizontal resolution, in pixels per meter, of the target device for the bitmap.
int biYPelsPerMeter; // Specifies the vertical resolution, in pixels per meter, of the target device for the bitmap.
unsigned int biClrUsed; // Specifies the number of color indexes in the color table actually used by the bitmap.
unsigned int biClrImportant; // Specifies the number of color indexes that are considered important for displaying the bitmap. If this value is zero, all colors are important.
} BITMAPINFOHEADER;
typedef struct tagRGBPIXEL{
unsigned char b;
unsigned char g;
unsigned char r;
} rgbPIXEL;
#pragma pack(pop)
typedef struct tagBITMAP{
BITMAPFILEHEADER FILEHEADER;
BITMAPINFOHEADER INFOHEADER;
rgbPIXEL* IMAGEDATA;
}BITMAP;
void main (){
string sImageLocation = "C:/BMP.bmp";
BITMAP bmpImage;
FILE* fbmpImage = NULL;
unsigned int ImagePixelAmount = 0;
bool bImageLoaded = false;
do{
//Open the image file
fopen_s(&fbmpImage, sImageLocation.c_str(), "rb");
//Check whether the image could be loaded successfully or not
if(fbmpImage == NULL){
cout << "Loading the image file failed!" << " " << endl;
}
if(fbmpImage != NULL){
cout << "Loaded the image file successfully!" << endl;
bImageLoaded = true;
}
cout << endl;
cout << endl;
cout << endl;
//Read the BITMAP FILE HEADER
fseek(fbmpImage, 0, SEEK_SET);
fread(&bmpImage.FILEHEADER, sizeof(BITMAPFILEHEADER), 1, fbmpImage);
//Check if the image is a valid bitmap file
if(bmpImage.FILEHEADER.bfType != 19778){
bImageLoaded = false;
cout << "Image is not a valid Bitmap file!" << endl;
fclose(fbmpImage);
}
}while(bImageLoaded = false);
//Show the information of the BITMAP FILE HEADER in the consol
cout << "Bitmap File Header Data Values:" << endl;
cout << endl;
cout << "Image Type: " << bmpImage.FILEHEADER.bfType << endl;
cout << "Image Size: " << bmpImage.FILEHEADER.bfSize << " Bytes" << endl;
cout << "Reserved: " << bmpImage.FILEHEADER.bfReserved1 << endl;
cout << "Reserved: " << bmpImage.FILEHEADER.bfReserved2 << endl;
cout << "Byte Offset: " << bmpImage.FILEHEADER.bfOffBits << endl;
cout << endl;
cout << endl;
cout << endl;
//Read the BITMAP INFO HEADER
fread(&bmpImage.INFOHEADER, sizeof(BITMAPINFOHEADER), 1, fbmpImage);
cout << "Bitmap Info Header Data Values: " << endl;
cout << endl;
cout << "Size of Bitmap Info Header: " << bmpImage.INFOHEADER.biSize << " Bytes" << endl;
cout << "Width of Bitmap: " << bmpImage.INFOHEADER.biWidth << " Pixel" << endl;
cout << "Height of Bitmap: " << bmpImage.INFOHEADER.biHeight << " Pixel" << endl;
cout << "Size of Image Data: " << bmpImage.INFOHEADER.biHeight << " Bytes" << endl;
cout << "Bit Count: " << bmpImage.INFOHEADER.biBitCount << " Bits Per Pixel" << endl;
cout << "Amount of color indexes: " << bmpImage.INFOHEADER.biClrUsed << endl;
cout << "Compression: " << bmpImage.INFOHEADER.biCompression << endl;
cout << endl;
cout << endl;
cout << endl;
ImagePixelAmount = bmpImage.INFOHEADER.biHeight * bmpImage.INFOHEADER.biWidth;
//Create space in memory and read in pixel data from the image
bmpImage.IMAGEDATA = (rgbPIXEL*)malloc(sizeof(rgbPIXEL) * ImagePixelAmount);
cout << "Memory for image created" << endl;
fseek(fbmpImage, bmpImage.FILEHEADER.bfOffBits, SEEK_SET);
fread(bmpImage.IMAGEDATA, ImagePixelAmount * sizeof(rgbPIXEL), 1, fbmpImage);
fclose(fbmpImage);
//Show the pixel data in the consol in numbers instead of ASCII-symbols
for(int y =0; y < bmpImage.INFOHEADER.biHeight; y++){
for(int x = 0; x < bmpImage.INFOHEADER.biWidth; x++){
cout << "Red: " <<(unsigned int) bmpImage.IMAGEDATA[y * bmpImage.INFOHEADER.biWidth + x].r << " ";
cout << "Green: " <<(unsigned int) bmpImage.IMAGEDATA[y * bmpImage.INFOHEADER.biWidth + x].g << " ";
cout << "Blue: " <<(unsigned int) bmpImage.IMAGEDATA[y * bmpImage.INFOHEADER.biWidth + x].b << " ";
}
cout << endl;
}
cout << endl;
cout << endl;
cout << endl;
cout << "Press any key to quit the programm" << endl;
_getch();
return;
}
更新：
根据 Hans Passant 的说法，我将代码更改为加载 24 位位图。使用红色位图，我会假设每个像素的打印值是red = 255, green = 0 and blue = 0. 但是，我收到的每个像素的实际值是red = 237, green = 28 and blue = 36. 对于任何其他图像，我都有同样的麻烦。