int loadBitmapFromFile(const char *filePath, U8 **bits)
{
    FILE *fp = fopen(filePath, "rb");
    if (fp == NULL) {
        return 0;
    }
    BITMAPFILEHEADER bfh;
    if (fread(&bfh, sizeof(bfh), 1, fp) != 1) {
        fclose(fp);
        return 0;
    }
    BITMAPINFOHEADER bih;
    if (fread(&bih, sizeof(bih), 1, fp) != 1) {
        fclose(fp);
        return 0;
    }
    if (bih.biBitCount != 8) {
        fclose(fp);
        printf("unsupported bitmap format.\n");
        return 0;
    }
    fseek(fp, bfh.bfOffBits - sizeof(bfh) - sizeof(bih), SEEK_CUR);  //将文件指针移动到离当前位置（调色板大小）字节处
    int imageSize = (bih.biWidth + 3) / 4 * 4 * bih.biHeight;
    U8 *buffer = (U8 *)malloc(imageSize);
    if (fread(buffer, 1, imageSize, fp) != imageSize) {
        fclose(fp);
        return 0;
    }

    fclose(fp);

    *bits = buffer;

    return imageSize;
}