Bmp行程编码C++文件类

以下是一个简单的C++文件类，可用于读取BMP文件并进行行程编码压缩。注意，此示例只支持24位无压缩BMP格式文件。

#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

// BMP文件头结构体
#pragma pack(push, 1) // 关闭结构体字节对齐
struct BMPHeader
{
    char bfType[2];
    unsigned int bfSize;
    unsigned short bfReserved1;
    unsigned short bfReserved2;
    unsigned int bfOffBits;
};
#pragma pack(pop) // 恢复结构体字节对齐

// BMP信息头结构体
#pragma pack(push, 1) // 关闭结构体字节对齐
struct BMPInfoHeader
{
    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;
};
#pragma pack(pop) // 恢复结构体字节对齐

// RGB颜色结构体
#pragma pack(push, 1) // 关闭结构体字节对齐
struct RGBColor
{
    unsigned char blue;
    unsigned char green;
    unsigned char red;
};
#pragma pack(pop) // 恢复结构体字节对齐

// 行程编码的像素结构体
#pragma pack(push, 1) // 关闭结构体字节对齐
struct RLEPixel
{
    unsigned char count; // 连续像素的数量
    RGBColor color; // 颜色值
};
#pragma pack(pop) // 恢复结构体字节对齐

// BMP文件类
class BMPFile
{
public:
    BMPFile() {}
    ~BMPFile() {}

    // 读取BMP文件
    bool read(const char* filename)
    {
        ifstream file(filename, ios::binary);
        if (!file)
        {
            cerr << "Error: Failed to open file " << filename << endl;
            return false;
        }

        BMPHeader header;
        file.read((char*)&header, sizeof(BMPHeader));

        BMPInfoHeader infoHeader;
        file.read((char*)&infoHeader, sizeof(BMPInfoHeader));

        if (header.bfType[0] != 'B' || header.bfType[1] != 'M')
        {
            cerr << "Error: Invalid file format" << endl;
            return false;
        }

        if (infoHeader.biCompression != 0)
        {
            cerr << "Error: Unsupported BMP format" << endl;
            return false;
        }

        width = infoHeader.biWidth;
        height = infoHeader.biHeight;
        int rowSize = (width * 3 + 3) / 4 * 4; // 每行像素数据的字节数，需要按照4字节对齐
        int imageSize = rowSize * height; // 图像数据区的大小

        pixels.resize(width * height);

        file.seekg(header.bfOffBits, ios::beg); // 定位到像素数据区

        for (int i = 0; i < height; i++)
        {
            RGBColor* row = &pixels[(height - i - 1) * width]; // 由于BMP文件的像素数据是从下到上存储的，所以需要反向读取

            for (int j = 0; j < width; j++)
            {
                RGBColor color;
                file.read((char*)&color, sizeof(RGBColor));
                row[j] = color;
            }

            file.seekg(rowSize - width * sizeof(RGBColor), ios::cur); // 跳过4字节对齐的填充数据
        }

        file.close();

        return true;
    }

    // 将BMP文件进行行程编码压缩，并保存为新的BMP文件
    bool compress(const char* filename)
    {
        ofstream file(filename, ios::binary);
        if (!file)
        {
            cerr << "Error: Failed to open file " << filename << endl;
            return false;
        }

        int rowSize = (width * 3 + 3) / 4 * 4; // 每行像素数据的字节数，需要按照4字节对齐
        int imageSize = rowSize * height; // 图像数据区的大小

        BMPHeader header;
        header.bfType[0] = 'B';
        header.bfType[1] = 'M';
        header.bfSize = sizeof(BMPHeader) + sizeof(BMPInfoHeader) + width * height * sizeof(RLEPixel);
        header.bfReserved1 = 0;
        header.bfReserved2 = 0;
        header.bfOffBits = sizeof(BMPHeader) + sizeof(BMPInfoHeader);

        BMPInfoHeader infoHeader;
        infoHeader.biSize = sizeof(BMPInfoHeader);
        infoHeader.biWidth = width;
        infoHeader.biHeight = height;
        infoHeader.biPlanes = 1;
        infoHeader.biBitCount = 24;
        infoHeader.biCompression = 0;
        infoHeader.biSizeImage = width * height * sizeof(RLEPixel);
        infoHeader.biXPelsPerMeter = 0;
        infoHeader.biYPelsPerMeter = 0;
        infoHeader.biClrUsed = 0;
        infoHeader.biClrImportant = 0;

        file.write((char*)&header, sizeof(BMPHeader));
        file.write((char*)&infoHeader, sizeof(BMPInfoHeader));

        vector<RLEPixel> rlePixels; // 存储行程编码后的像素数据

        for (int i = 0; i < height; i++)
        {
            RGBColor* row = &pixels[(height - i - 1) * width]; // 由于BMP文件的像素数据是从下到上存储的，所以需要反向读取

            int j = 0;
            while (j < width)
            {
                RLEPixel pixel;
                pixel.color = row[j];

                int count = 1;
                while (j + count < width && row[j + count].red == pixel.color.red && row[j + count].green == pixel.color.green && row[j + count].blue == pixel.color.blue && count < 255)
                {
                    count++;
                }

                pixel.count = count;
                rlePixels.push_back(pixel);

                j += count;
            }

            // 添加行终止标志
            RLEPixel endPixel;
            endPixel.count = 0;
            rlePixels.push_back(endPixel);
        }

        file.write((char*)rlePixels.data(), rlePixels.size() * sizeof(RLEPixel));

        file.close();

        return true;
    }

private:
    int width;
    int height;
    vector<RGBColor> pixels;
};

使用示例：

BMPFile bmpFile;
bmpFile.read("input.bmp");
bmpFile.compress("output.bmp");

其中，`input.bmp`为输入文件名，`output.bmp`为输出文件名。