linux下的显示设备就是/dev/fb0，往该设备写入的数据会显示在屏幕上，所以我们可以通过直接写frame buffer这个/dev/fb0设备来实现bmp图像的显示，而不用管是在shell文本方式下还是在其他gnome、qt、gtk、wayland等图形模式下，都能显示出来。当前前提是你的linux下必须具有该设备并支持读写（无特殊处理的linux都有该设备）。
代码（支持16位、24位或32位颜色深度的bmp图像，支持24或32位颜色深度的fb0设备）：
#include
#include
#include
#include
#include
#include
#include
#include
#include
//14byte文件头
typedef struct
{
charcfType[2];//文件类型，”BM”(0x4D42)
int cfSize;//文件大小（字节）
int cfReserved;//保留，值为0
int cfoffBits;//数据区相对于文件头的偏移量（字节）
}__attribute__((packed)) BITMAPFILEHEADER;
//__attribute__((packed))的作用是告诉编译器取消结构在编译过程中的优化对齐
//40byte信息头
typedef struct
{
charciSize[4];//BITMAPFILEHEADER所占的字节数
int ciWidth;//宽度
int ciHeight;//高度
charciPlanes[2];//目标设备的位平面数，值为1
int ciBitCount;//每个像素的位数
charciCompress[4];//压缩说明
charciSizeImage[4];//用字节表示的图像大小，该数据必须是4的倍数
charciXPelsPerMeter[4];//目标设备的水平像素数/米
charciYPelsPerMeter[4];//目标设备的垂直像素数/米
charciClrUsed[4]; //位图使用调色板的颜色数
charciClrImportant[4]; //指定重要的颜色数，当该域的值等于颜色数时（或者等于0时），表示所有颜色都一样重要
}__attribute__((packed)) BITMAPINFOHEADER;
static void FbUpdate(int fbfd, struct fb_var_screeninfo *vi) //将要渲染的图形缓冲区的内容绘制到设备显示屏来
{
vi->yoffset=0; //from 0 to yres will be display.
ioctl(fbfd, FBIOPUT_VSCREENINFO, vi);
}
static int CursorBitmapFormatConvert(char *dst, char *src, int screenXres, int screenYres, int bytes_per_pixel_screen,
intbmpWidth, intbmpHeight, intbytes_per_pixel_bitmap)
{
int i ,j ;
char*psrc = src ;
char*pdst = dst;
char*p = psrc;
int oldi =0;
int left_right = (screenXres-bmpWidth)/2;
int top_bottom = (screenYres-bmpHeight)/2;
printf(“left_right: %d, top_bottom: %d\n”, left_right, top_bottom);
printf(“screenXres: %d, screenYres: %d\n”, screenXres, screenYres);
printf(“bmpWidth: %d, bmpHeight: %d\n”, bmpWidth, bmpHeight);
if(left_right <0&& top_bottom <0){
printf(“error: BMP is too big, screen X: %d, Y: %d, bmp width: %d, height: %d\n”, screenXres, screenYres, bmpWidth, bmpHeight);
return-1;
}
/* 由于bmp存储是从后面往前面，所以需要倒序进行转换 */
pdst += (screenXres * bmpHeight * bytes_per_pixel_screen);
pdst += (screenXres * top_bottom * bytes_per_pixel_screen); //move to middle bmpHeight
for(i=0; i p = psrc + (i+1) * bmpWidth * bytes_per_pixel_bitmap; if(i ==0) pdst -= (left_right * bytes_per_pixel_screen); //move to middle bmpWidth else pdst -= (left_right * 2 * bytes_per_pixel_screen); //move to middle bmpWidth for(j=0; j pdst -= bytes_per_pixel_screen; p -= bytes_per_pixel_bitmap; int kk =0; int k; for(k=0; k if(kk >= bytes_per_pixel_bitmap) pdst[k] =255; // 3: alpha color else pdst[k] =p[kk]; // 0: blue, 1: green, 2: red kk++; } } } pdst -= (left_right * bytes_per_pixel_screen); // move to 0 position return0; } int ShowBmp(char *path, int fbfd, struct fb_var_screeninfo *vinfo, char *fbp) { int i; FILE *fp; int rc; int line_x, line_y; longint location =0, BytesPerLine =0; char*bmp_buf =NULL; char* buf =NULL; int flen =0; int ret =-1; int total_length =0; BITMAPFILEHEADER FileHead; BITMAPINFOHEADER InfoHead; int width, height; printf(“into ShowBmp function\n”); if(path ==NULL) { printf(“path Error,return\n”); return-1; } printf(“path = %s\n”, path); fp = fopen( path, “rb” ); if(fp ==NULL){ printf(“load cursor file open failed\n”); return-1; } /* 求解文件长度 */ fseek(fp,0,SEEK_SET); fseek(fp,0,SEEK_END); flen = ftell(fp); printf(“flen is %d\n”,flen); bmp_buf = (char*)calloc(1,flen – 54); if(bmp_buf ==NULL){ printf(“load > malloc bmp out of memory!\n”); return-1; } /* 再移位到文件头部 */ fseek(fp,0,SEEK_SET); rc = fread(&FileHead, sizeof(BITMAPFILEHEADER),1, fp); if ( rc !=1) { printf(“read header error!\n”); fclose( fp ); return( -2 ); } //检测是否是bmp图像 if (memcmp(FileHead.cfType, “BM”, 2) !=0) { printf(“it’s not a BMP file\n”); fclose( fp ); return( -3 ); } rc = fread( (char *)&InfoHead, sizeof(BITMAPINFOHEADER),1, fp ); if ( rc !=1) { printf(“read infoheader error!\n”); fclose( fp ); return( -4 ); } width = InfoHead.ciWidth; height = InfoHead.ciHeight; printf(“FileHead.cfSize =%d byte\n”,FileHead.cfSize); printf(“flen = %d\n”, flen); printf(“width = %d, height = %d\n”, width, height); //跳转的数据区 fseek(fp, FileHead.cfoffBits, SEEK_SET); printf(” FileHead.cfoffBits = %d\n”, FileHead.cfoffBits); printf(” InfoHead.ciBitCount = %d\n”, InfoHead.ciBitCount); int bytes_per_pixel_bitmap =InfoHead.ciBitCount/8; total_length = width * height * bytes_per_pixel_bitmap; printf(“total_length = %d\n”, total_length); //每行字节数 buf = bmp_buf; while ((ret =fread(buf,1,total_length,fp)) >=0) { if (ret ==0) { usleep(100); continue; } printf(“ret = %d\n”, ret); buf = ((char*) buf) + ret; total_length = total_length – ret; if(total_length ==0) break; } CursorBitmapFormatConvert(fbp, bmp_buf, (*vinfo).xres, (*vinfo).yres, (*vinfo).bits_per_pixel/8, width, height, bytes_per_pixel_bitmap); free(bmp_buf); fclose(fp); printf(“show logo return 0\n”); return0; } int ShowPicture(int fbfd, char *path) { struct fb_var_screeninfo vinfo; struct fb_fix_screeninfo finfo; longint screensize =0; struct fb_bitfield red; struct fb_bitfield green; struct fb_bitfield blue; //打开显示设备 printf(“fbfd = %d\n”, fbfd); if (fbfd ==-1) { //printf(“Error opening frame buffer errno=%d (%s)\n”,errno, strerror(errno)); return-1; } if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) { //printf(“Error：reading fixed information.\n”); return-1; } if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) { //printf(“Error: reading variable information.\n”); return-1; } //printf(“R:%x ;G:%d ;B:%d \n”, (int)vinfo.red, vinfo.green, vinfo.blue ); printf(“%dx%d, %dbpp\n”, vinfo.xres, vinfo.yres, vinfo.bits_per_pixel ); //计算屏幕的总大小（字节） screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8; printf(“screensize=%ld byte\n”,screensize); //对象映射 char*fbp = (char*)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0); if (fbp == (char*)-1) { printf(“Error: failed to map framebuffer device to memory.\n”); return-1; } printf(“sizeof file header=%ld\n”, sizeof(BITMAPFILEHEADER)); //显示图像 ShowBmp(path, fbfd, &vinfo, fbp); FbUpdate(fbfd, &vinfo); ///在屏幕上显示多久 sleep(10); //删除对象映射 munmap(fbp, screensize); return0; } int main() { int fbfd =0; fbfd = open(“/dev/fb0”, O_RDWR); if (!fbfd) { printf(“Error: cannot open framebuffer device.\n”); return-1; } ShowPicture(fbfd, “/tmp/license_ckx.bmp”); close(fbfd); return0; }