save RGB24 frame to bmp file.

rgb24ToBMP.cpp

void rgb24ToBMP(unsigned char *rgbBuffer, int width, int height, const char *bmppath) {
    typedef struct {  
        long imageSize;
        long blank;
        long startPosition;
    } BmpHead;

    typedef struct {
        long  Length;
        long  width;
        long  height;
        unsigned short  colorPlane;
        unsigned short  bitColor;
        long  zipFormat;
        long  realSize;
        long  xPels;
        long  yPels;
        long  colorUse;
        long  colorImportant;
    } InfoHead;

    int i = 0, j = 0;
    BmpHead m_BMPHeader = { 0 };
    InfoHead  m_BMPInfoHeader = { 0 };
    char bfType[2] = { 'B','M' };
    int header_size = sizeof(bfType) + sizeof(BmpHead) + sizeof(InfoHead);
    FILE *fp_bmp = NULL;

    if((fp_bmp = fopen(bmppath, "wb")) == NULL) {
        printf("Error: Cannot open output BMP file.\n");
        return;
    }

    m_BMPHeader.imageSize = 3 * width*height + header_size;
    m_BMPHeader.startPosition = header_size;

    m_BMPInfoHeader.Length = sizeof(InfoHead);
    m_BMPInfoHeader.width = width;
    //BMP storage pixel data in opposite direction of Y-axis (from bottom to top).
    m_BMPInfoHeader.height = -height;
    m_BMPInfoHeader.colorPlane = 1;
    m_BMPInfoHeader.bitColor = 24;
    m_BMPInfoHeader.realSize = 3 * width*height;

    fwrite(bfType, 1, sizeof(bfType), fp_bmp);
    fwrite(&m_BMPHeader, 1, sizeof(m_BMPHeader), fp_bmp);
    fwrite(&m_BMPInfoHeader, 1, sizeof(m_BMPInfoHeader), fp_bmp);

    for(j = 0; j < height; j++) {
        for(i = 0; i < width; i++) {
            char temp = rgbBuffer[(j*width + i) * 3 + 2];
            rgbBuffer[(j*width + i) * 3 + 2] = rgbBuffer[(j*width + i) * 3 + 0];
            rgbBuffer[(j*width + i) * 3 + 0] = temp;
        }
    }
    fwrite(rgbBuffer, 3 * width*height, 1, fp_bmp);
    fclose(fp_bmp);
    printf("Finish generate %s!\n", bmppath);
    return;
}