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, number of color used and number of significant color, compression method, bit count per pixel etc.