整理:android 读取 屏幕 图形 fb0

<h2 class="titName SG_txta" style="">Android下截屏 及 格式转换</h2>

/dev/graphics/fb0 fb0

dd bs=$((320*320*2)) count=2 if=fb0 of=screenshot1.xmp

./565to888 <screenshot1.xmp >screenshot888.xmp

convert -depth 8 -size 216x204 rgb:screenshot888.xmp  screenshot888.png

#display /tmp/screenshot888.png

http://wiseideal.iteye.com/blog/1250175

#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>


int version = 0;

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;
    long 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("id %s\n",finfo.id);       //s3c2410fb
    printf("smem_start %ld\n",finfo.smem_start); //帧缓冲 内存开始地址,物理地址
    printf("smem_len %d\n",finfo.smem_len); // 帧缓冲 内存 长度
    printf("type %d\n",finfo.type);
    printf("type_aux %d\n",finfo.type_aux);//平面交织交替
    printf("visual %d\n",finfo.visual); //记录 色彩模式   2
    printf("xpanstep %d\n",finfo.xpanstep);//如果没有硬件panning，赋0
    printf("ypanstep %d\n",finfo.ypanstep);
    printf("line_length %d\n",finfo.line_length);    //640
    printf("mmio_start %ld\n",finfo.mmio_start);//内存映射IO开始地址 物理地址
    printf("mmio_len %d\n",finfo.mmio_len);//内存映射IO 长度
    printf("accel %d\n\n",finfo.accel);
    

    printf("xres %d\n",vinfo.xres); //可见解析度  320
    printf("yres %d\n",vinfo.yres);            //240
    printf("xres_virturl %d\n",vinfo.xres_virtual); //虚拟解析度  320
    printf("yres_virtual %d\n",vinfo.yres_virtual);              //240
    printf("xoffset %d\n",vinfo.xoffset); //虚拟到可见的偏移        0
    printf("yoffset %d\n",vinfo.yoffset);                        // 0
    printf("bits_per_pixel %d\n",vinfo.bits_per_pixel); //每像素位数 bpp  16
    printf("grayscale %d\n",vinfo.grayscale);//非零时，指灰度
    
    printf("fb_bitfield red.offset %d\n",vinfo.red.offset);     //11  偏移11位
    printf("fb_bitfield .length %d\n",vinfo.red.length);        // 5
    printf("fb_bitfield .msb_right %d\n",vinfo.red.msb_right);  //  0
    printf("fb_bitfield green.offset %d\n",vinfo.green.offset);  //5 偏移5位
    printf("fb_bitfield .length %d\n",vinfo.green.length);       // 6
    printf("fb_bitfield .msb_right %d\n",vinfo.green.msb_right); // 0
    printf("fb_bitfield blue.offset %d\n",vinfo.blue.offset);
    printf("fb_bitfield .length %d\n",vinfo.blue.length);
    printf("fb_bitfield .msb_right %d\n",vinfo.blue.msb_right);
    printf("fb_bitfield transp.offset %d\n",vinfo.transp.offset);
    printf("fb_bitfield .length %d\n",vinfo.transp.length);
    printf("fb_bitfield .msb_right %d\n",vinfo.transp.msb_right);

    printf("nonstd %d\n",vinfo.nonstd); //!=0 非标准像素格式
    printf("activate %d\n",vinfo.activate);
    printf("height %d\n",vinfo.height); //高度/  240
    printf("widht %d\n",vinfo.width);   //          320
    printf("accel_flags %d\n",vinfo.accel_flags); //看 fb_info.flags

    //定时，除了 pixclock之外，其他的都以像素时钟为单位
    printf("pixclock %d\n",vinfo.pixclock);//像素时钟，皮秒   80000
    printf("left_margin %d\n",vinfo.left_margin);//行切换：从同步到绘图之间的延迟    28
    printf("right_margin %d\n",vinfo.right_margin);//行切换：从绘图到同步之间的延迟   24
    printf("upper_margin %d\n",vinfo.upper_margin);//帧切换：从同步到绘图之间的延迟   6
    printf("lower_margin %d\n",vinfo.lower_margin);//帧切换：从绘图到同步之间的延迟    2

    printf("hsync_len %d\n",vinfo.hsync_len); //hor 水平同步的长度         42
    printf("vsync_len %d\n",vinfo.vsync_len); //vir 垂直同步的长度         12

    printf("sync %d\n",vinfo.sync); //
    printf("vmode %d\n",vinfo.vmode);
    printf("rotate %d\n",vinfo.rotate);
	



    // Figure out the size of the screen in bytes
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;;
	printf("screensize = %ld\n", screensize);

    // Map the device to memory
    fbp = (char *)mmap(0, screensize*2, 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");

	
	/*


	printf("White Screen\n");
	//while(1)
	{

		for(x =0;x<640*5;x+=2)
		{

			*((unsigned short int*)(fbp + x)) = 0xffff;
			
		}
		usleep(200);

	}


	for(x =0;x<640;x+=2)
	{

		y =*((unsigned short int*)(fbp + x));		
		printf("x = %lx, temp = %lx\n", x, y);

	}

*/	

		

 //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 = %ld\n", x, location);
        //sleep to see it
        usleep(200);
    }

    //clean framebuffer
    munmap(fbp, screensize);
    close(fbfd);
	
	version =16;
	printf("version %d  %s\n",version,__TIME__);

    return 0;
}

http://blog.youkuaiyun.com/louiswangbing/article/details/6655040