qt 生成4bit的BMP图片

如下代码展示如何生成一个像素占4bit的图片。

CImage oFourBit;
    const RGBQUAD tab[16] = {
        {0,0,0,0},       {36,36,36,0},    {72,72,72,0},    {108,108,108,0},
        {144,144,144,0}, {180,180,180,0}, {216,216,216,0}, {255, 255, 255, 0},
        {0,0,0,0},       {36,36,36,0},    {72,72,72,0},    {108,108,108,0},
        {144,144,144,0}, {180,180,180,0}, {216,216,216,0}, {255, 255, 255, 0}
    };
    int width = 1600;int height = 1600;
    oFourBit.Create(1600, 1600, 4); // Create and attach a bitmap
    oFourBit.SetColorTable(0, 16, tab);

    byte *pImg = (byte *)oFourBit.GetBits();
    int step = oFourBit.GetPitch();
    for (int i = 0; i < width; i++)
    {
        for (int j = 0; j < height; j++)
        {
            if(i < 200)
            {
                *(pImg + i*step + j) = 0;
            }
            else if( i > 200 && i < 400)
            {
                *(pImg + i*step + j) = 1;
            }
            else if( i > 400 && i < 600)
            {
                *(pImg + i*step + j) = 2;
            }
            else if( i > 600 && i < 800)
            {
                *(pImg + i*step + j) = 3;
            }
            else if( i > 800 && i < 1000)
            {
                *(pImg + i*step + j) = 4;
            }
            else if( i > 1000 && i < 1200)
            {
                *(pImg + i*step + j) = 5;
            }
            else if( i > 1200 && i < 1400)
            {
                *(pImg + i*step + j) = 6;
            }
            else
                *(pImg + i*step + j) = 7;

        }
    }
    oFourBit.Save(_T("c.bmp"),Gdiplus::ImageFormatBMP);

像素的值跟平时处理图片的灰度值有所不同，他的值是代表颜色标中的索引，解析的时候调色盘需要一致。

图片