c++ - C++ 在 C++ 中将 24bpp 位图转换为 8bpp 位图

Question

我想将 24bpp 位图文件转换为 8bpp 位图文件。源文件已转换为单色图像（以编程方式），现在我必须将其更改为 8bpp 格式。我使用的是 ubuntu 10.10，所以我不能使用 Windows 库。我也不想使用第三方库。这是在 C++ 中。我尝试了很多方法，但在读取 3 个字节并写入 1 个字节时总是出错。最终结果始终包含全白图像。请帮助解决这个问题。

 unsigned char* currentPixel;
 unsigned char* currentRow;

    for(int i = 0; i < height; i++)
        {
            currentRow = &pixels[i * rowStride];
            for(int j = 0; j < width; j++)
            {
                currentPixel = &pixels[i * rowStride + j * n_channels];


                float fThreshold = 125.0f;

                float g = (float)currentPixel[0];
                float b = (float)currentPixel[1];
                float r = (float)currentPixel[2];

                float rMul = 0.299f; //0.212f
                float gMul = 0.587f; //0.7154f
                float bMul = 0.114f; //0.0721f

                float f = ( rMul * r) + ( gMul * g) + ( bMul * b);
                float fPixel = 0.0;
                if(f > fThreshold)
                {
                    currentPixel[0] = (0xFF);
                    currentPixel[1] = (0xFF);
                    currentPixel[2] = (0xFF);
                    newData->push_back((0xFF));
                    zeroCount++;
                }
                else
                {
                    currentPixel[0] = (0x00);
                    currentPixel[1] = (0x00);
                    currentPixel[2] = (0x00);
                    newData->push_back((0x00));
                    oneCount++;
                }

                //newData->push_back((uint8_t)currentPixel[0]);
                //newData->push_back((uint8_t)currentPixel[1]);
                //newData->push_back((uint8_t)currentPixel[2]);

                //cout<<"f : "<<f<<" fPixel : "<<fPixel<<endl;
            }