framebuffer渐变进度条

framebuffer渐变进度条 虽然现在能通过交叉环境编译程序，并push到Android上执行，但那只是console台程序，是不是有些单调呢,下面就要看如何通过 Linux的 framebuffer 技术在Android上画图形，关于Linux的framebuffer技术，这里就不再详细讲解了，请大家google一下。 操作framebuffer的主要步骤如下: 1、打开一个可用的FrameBuffer设备; 2、通过mmap调用把显卡的物理内存空间映射到用户空间; 3、更改内存空间里的像素数据并显示; 4、退出时关闭framebuffer设备。 下面的这个例子简单地用framebuffer画了一个渐变的进度条，代码 framebuf.c 如下: 引用 #include #include #include #include #include inline static unsigned short int make16color(unsigned char r, unsigned char g, unsigned char b) { return ( (((r >> 3) & 31) << 11) | (((g >> 2) & 63) << 5) | ((b >> 3) & 31) ); } int main() { int fbfd = 0; struct fb_var_screeninfo vinfo; struct fb_fix_screeninfo finfo; long int screensize = 0; char *fbp = 0; int x = 0, y = 0; int guage_height = 20, step = 10; long int location = 0; // Open the file for reading and writing fbfd = open(”/dev/graphics/fb0″, O_RDWR); if (!fbfd) { printf(”Error: cannot open framebuffer device.\n”); exit(1); } printf(”The framebuffer device was opened successfully.\n”); // Get fixed screen information if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) { printf(”Error reading fixed information.\n”); exit(2); } // Get variable screen information if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) { printf(”Error reading variable information.\n”); exit(3); } printf(”sizeof(unsigned short) = %d\n”, sizeof(unsigned short)); printf(”%dx%d, %dbpp\n”, vinfo.xres, vinfo.yres, vinfo.bits_per_pixel ); printf(”xoffset:%d, yoffset:%d, line_length: %d\n”, vinfo.xoffset, vinfo.yoffset, finfo.line_length ); // Figure out the size of the screen in bytes screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;; // Map the device to memory fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0); if ((int)fbp == -1) { printf(”Error: failed to map framebuffer device to memory.\n”); exit(4); } printf(”The framebuffer device was mapped to memory successfully.\n”); //set to black color first memset(fbp, 0, screensize); //draw rectangle y = (vinfo.yres - guage_height) / 2 - 2; // Where we are going to put the pixel for (x = step - 2; x < vinfo.xres - step + 2; x++) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; *((unsigned short int*)(fbp + location)) = 255; } y = (vinfo.yres + guage_height) / 2 + 2; // Where we are going to put the pixel for (x = step - 2; x < vinfo.xres - step + 2; x++) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; *((unsigned short int*)(fbp + location)) = 255; } x = step - 2; for (y = (vinfo.yres - guage_height) / 2 - 2; y < (vinfo.yres + guage_height) / 2 + 2; y++) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; *((unsigned short int*)(fbp + location)) = 255; } x = vinfo.xres - step + 2; for (y = (vinfo.yres - guage_height) / 2 - 2; y < (vinfo.yres + guage_height) / 2 + 2; y++) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; *((unsigned short int*)(fbp + location)) = 255; } // Figure out where in memory to put the pixel for ( x = step; x < vinfo.xres - step; x++ ) { for ( y = (vinfo.yres - guage_height) / 2; y < (vinfo.yres + guage_height) / 2; y++ ) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; if ( vinfo.bits_per_pixel == 32 ) { *(fbp + location) = 100; // Some blue *(fbp + location + 1) = 15+(x-100)/2; // A little green *(fbp + location + 2) = 200-(y-100)/5; // A lot of red *(fbp + location + 3) = 0; // No transparency } else { //assume 16bpp unsigned char b = 255 * x / (vinfo.xres - step); unsigned char g = 255; // (x - 100)/6 A little green unsigned char r = 255; // A lot of red unsigned short int t = make16color(r, g, b); *((unsigned short int*)(fbp + location)) = t; } } //printf(”x = %d, temp = %d\n”, x, temp); //sleep to see it usleep(200); } //clean framebuffer munmap(fbp, screensize); close(fbfd); return 0; } 注意，在Android环境，framebuffer设备不是象linux一样的 /dev/fb0，而是 /dev/graphics/fb0 ， fbfd = open(”/dev/graphics/fb0″, O_RDWR); 打开framebuffer设备， fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0); 将设备map到一块内存，然后就可以操作这块内存空间来显示你想画的图形了。 最后别忘了关闭设备: munmap(fbp, screensize); close(fbfd);