直接读写fb0测试
1 写fb0
修改 system/extras/tests/framebuffer/fb_test.c
读取格式为RGB_888的bmp图片，显示到屏幕上
void draw_grid(int w, int h, void* _loc) {
int i, j;
int v;
int stride = fi.line_length / (vi.bits_per_pixel >> 3);
uint16_t *loc = _loc;
uint32_t *loc32 = _loc;
BMP_READ * bmp = bmp_open("test.bmp");
if (bmp == NULL)
{
printf("bmp_open error \n");
return;
}
int bmpWideth = bmp->u.r8888.i.biWidth;
//the giving data
unsigned char* pos = bmp->pdata;
printf("pos[0] = %d %d %d \n", *pos, *(pos+1), *(pos+2) );
printf("data size = %d\n", bmp->dataSize);
printf("data type = %d\n", bmp->tpye);
int bpp = 3;
if (bmp->tpye == eRGBX_8888)
{
bpp = 4;
}
printf("bytes per pix = %d\n", bpp);
int pix = 0;
unsigned char r, g, b;
//scan each row, so loop the height first
for (j = 0; j < 700; j++)
{
for (i = 0; i < bmpWideth; i++)
{
b = *pos & 0xff;;
g = *(pos + 1) & 0xff;
r = *(pos + 2) & 0xff;
pix = r | (g << 8) | (b << 16) | (0xff << 24);
loc32[i + j*(stride)] = pix;
pos += bpp;//3
}
}
执行结果
Unknown:/data/local/tmp # ./test-fb-simple
vi.xres = 720
vi.yres = 1280
vi.xresv = 736
vi.yresv = 2560
vi.xoff = 0
vi.yoff = 0
vi.bits_per_pixel = 32
fi.line_length = 2944
fi.smem_len = 11304960
fi.type = 0
====== fb_bitfield red.offset : 0
====== fb_bitfield red.length : 8
====== fb_bitfield red.msb_right : 0
====== fb_bitfield green.offset : 8
====== fb_bitfield green.length : 8
====== fb_bitfield green.msb_right : 0
====== fb_bitfield blue.offset : 16
====== fb_bitfield blue.length : 8
====== fb_bitfield blue.msb_right : 0
====== fb_bitfield transp.offset : 24
====== fb_bitfield transp.length : 8
====== fb_bitfield transp.msb_right : 0
active buffer: 0
check_bmp : bmp width(500) or height(747)
check_bmp : 24 eRGBX_888
bmp->header.bfOffBits = 54
bmp->dataSize = 1120500
pos[0] = 25 46 78
data size = 1120500
data type = 2
active buffer: 1
active buffer: 0
Unknown:/data/local/tmp #
在屏幕左上方显示了图片，由于bmp图片的存储格式有正常和倒置2种数据存放方式，这里测试图片是倒置存放的，我们的程序是直接显示，没有根据h的正负值进行处理，所以 看上去倒置了，但是，我们的试验结果已经出来了。
2 读fb0保存数据
早期的Android中，截图操作就是直接读取fb0，但是，现在这样的操作已经行不通了，因为显示系统的设计比较复杂了，有多缓冲等机制，不再是单纯的framebuffer机制，直接获取到的图片可能是静态的，也可能是混乱的图片。
（可以看到，获取到的图片没有状态栏 statusbar， 透明度也异常）
