读取BMP文件信息和显示，读取文件头信息，包括大小，长宽，水平和垂直分辨率，彩色数目，实际用到的彩色数目，关键颜色数目，压缩方式，每像素用到的bit数等-to read and display bmp file. output the header information, includnig file size, image width and height, horizontal and verticular resolution,