Question

我有问题！我想获得24位位图中每个像素的RGB信息。直到现在我写了一个代码，它获取有关位图的信息，但我有关于每个像素的gettin RGB信息的问题。我想将这些信息保存在Pixel的结构像素中。你能帮帮我吗？

我把我的代码放在下面：

     #include <iostream>
#include <fstream>
#include <conio.h>

using namespace std;

#pragma pack(2)

struct BITMAPFILEHEADER             // File header
{ 
  char bfType[2];                   // File type: should be BM ( 0x42 0x4D ) 
  int bfSize;                       // File size in bytes
  short bfReserved1;                // Reserved - for what i have no idea :P 
  short bfReserved2;                // -||-
  int bfOffBits;                    // Offset, adress of the beginning of the information about image (pixels )
};

struct BITMAPINFOHEADER             // Bitmap header
{
  unsigned int biSize;              // Size of this header
  unsigned int biWidth;             // Width of image ( in pixels)
  unsigned int biHeight;            // Height of this image ( in pixels )
  unsigned short biPlanes;          // Numer of color planes, always 1
  unsigned short biBitCount;        // Number of bytes for pixel. Possibility values :1,4,8,16, 24 and 32
  unsigned int biCompression;       // Used compression (0 -none)
  unsigned int biSizeImage;         // Size of image 
  signed int biXPelsPerMeter;       // Horizontal resolution of the image (pixel per meter)
  signed int biYPelsPerMeter;       // Vertical resolution of the image (pixel per meter)
  unsigned int biClrUsed;           // Number of colors in the color palette, or 0 to default to 2^n ( 0- no palette)
  unsigned int biClrImportant;      // Number of important colors used
};



#pragma pack(push, 1)

struct Pixel{
    unsigned int blue;  // or double?
    unsigned int green;
    unsigned int red;
    //unsigned char reserved;
};
#pragma pack(pop)

int main(){

    // Openning the file

    cout << "Openning the file for reading: "<< endl;
    _getch();
    ifstream ifs("moj.bmp", ios::binary);

    if(!ifs){
        cout << " There is no such of file ";
        _getch();
        return 0;   
    } 

    // Reading information about BITMAPFILEHEADER
    char* temp = new char[sizeof(BITMAPFILEHEADER)];
    ifs.read(temp, sizeof(BITMAPFILEHEADER));
    BITMAPFILEHEADER* bfh = (BITMAPFILEHEADER*)(temp);

    cout << "\n FILHEADER\n";
    cout << "\n File type: " << bfh->bfType[0] << bfh->bfType[1] << endl;
    cout << " File size: " << bfh->bfSize << endl;
    cout << " Offset(adress of beggining of the image information): " << bfh->bfOffBits << endl;
    _getch();


    // Reading information about BITMAPINFOHEADER
    temp = new char[sizeof(BITMAPINFOHEADER)];
    ifs.read(temp, sizeof(BITMAPINFOHEADER));
    BITMAPINFOHEADER* bih = (BITMAPINFOHEADER*)(temp);

    cout << "\n INFOHEADER\n";
    cout << "\n Header size: " << bih->biSize << endl;
    cout << " Image width: " << bih->biWidth << endl;
    cout << " Image height: " << bih->biHeight << endl;
    cout << " Number of bytes for pixel: " << bih->biBitCount << endl;
    cout << " Used compression: " << bih->biCompression << endl;
    cout << " Image size: " << bih->biSizeImage<< endl;
    cout << " Horizontal resolution: " << bih->biXPelsPerMeter << endl;
    cout << " Vertical resolution: " << bih->biYPelsPerMeter << endl;
    cout << " Number of colors in the color palette: " << bih->biClrUsed << endl;
    cout << " Number of important colors used: " << bih->biClrImportant << endl;
    _getch();

    Pixel** pixs = new Pixel*[bih->biHeight];
    for (int i = 0; i < bih->biHeight ; ++i)
        pixs[i] = new Pixel[bih->biWidth];


    ifs.seekg(bfh->bfOffBits, ios::beg); // bfOffBits points for beginning of the image information


               /* I have no idea how to read pixel after pixel in this moment */


    _getch();

    for (int i = 0; i < bih->biHeight; ++i) 
        delete pixs[i];

    delete pixs;
    delete bfh;
    delete bih;

    return 0;

}

这是有效的，但我应该如何在某个整数变量上更改它？例如：

pixs[i][j]=(unsigned int)r;

无效。在pixs [i] [j]中输入此命令是一些垃圾......：/

也许有些建议？

Answer 1

如果偏移和图像尺寸并且您确定图像为24位（每种颜色为1字节），则可以逐像素地扫描图像缓冲区。

uint8_t* pixelTmp = new uint8_t[3];
for (int i = 0; i != imageSize; ++i) {
    ifs.read(pixelTmp, 3);
    pixelTmp[0]; /* is blue 0-255 */
    pixelTmp[1]; /* is green 0-255 */
    pixelTmp[2]; /* is red 0-255 */
}

将pixelTmp[0]的值分配给您自己的像素蓝色，依此类推......

Answer 2

如您所见{1}}，1个像素使用3个字节。这意味着第一个字节是蓝色，第二个是绿色，第三个是红色。你现在应该做的是循环遍历位图文件的其余部分，读取3个单独的字节，并将它们存储在你的结构中：

char r, g, b;
ifs.read(&b, 1);
ifs.read(&g, 1);
ifs.read(&r, 1);

您可以查看示例1以查看图像行的存储方式。

Answer 3

首先，biBitCount的{{1}}字段不每个像素的字节数，它是的数量位

这是您需要从原始数据中读取一个像素的位数。对于24位像素，只需按照Alessandro Pezzato或Ben的答案中的建议阅读。 32位像素包含一个额外的字节，通常包含一个alpha通道（像素的透明度。）有多种不同的16位格式，而8位格式通常是颜色表的索引。我不知道4位格式，但1位是纯黑白（0是黑色，1是白色。）

对于8位，16位，24位和32位格式，读取一到四个字节并根据颜色格式进行转换。对于小于8（4和1）的值，一次读取一个字节，然后在循环中使用掩码来获取这些位，并以内部格式存储。

如何在bmp中读取像素

3 个答案: