嵌入式linux通用截图工具

时间：2009-08-22 来源：lixianjing

嵌入式linux通用截图工具

转载时请注明出处和作者联系方式
文章出处：http://www.limodev.cn/blog
作者联系方式：李先静 <xianjimli at hotmail dot com>

为了截几张图片给broncho的A1做宣传，昨天写了一个截图工具。这个工具与其它截图工具不同的是，它不基于任何具体的GUI，直接从framebuffer中截图，然后保存为jpeg图片，所以适用于任何嵌入式linux设备。

o 打开framebuffer

static int fb_open(struct FB *fb, const char* fbfilename)
{
 fb->fd = open(fbfilename, O_RDWR);
 if (fb->fd < 0)
 {
 fprintf(stderr, "can't open %s\n", fbfilename);
 return -1;
 }
 
 if (ioctl(fb->fd, FBIOGET_FSCREENINFO, &fb->fi) < 0)
 goto fail;
 if (ioctl(fb->fd, FBIOGET_VSCREENINFO, &fb->vi) < 0)
 goto fail;
 
 fb->bits = mmap(0, fb_size(fb), PROT_READ | PROT_WRITE, 
 MAP_SHARED, fb->fd, 0);
 if (fb->bits == MAP_FAILED)
 goto fail;
 
 return 0;
fail:
 printf("%s is not a framebuffer.\n", fbfilename);
 close(fb->fd);
 
 return -1;
}

o 读取数据并写入jpeg

static int snap(const char * filename, int quality, struct FB* fb)
{
 int row_stride = 0; 
 FILE * outfile = NULL;
 JSAMPROW row_pointer[1] = {0};
 struct jpeg_error_mgr jerr = {0};
 struct jpeg_compress_struct cinfo = {0};
 
 cinfo.err = jpeg_std_error(&jerr);
 jpeg_create_compress(&cinfo);
 
 if ((outfile = fopen(filename, "wb+")) == NULL) 
 {
 fprintf(stderr, "can't open %s\n", filename);
 
 return -1;
 }
 
 jpeg_stdio_dest(&cinfo, outfile);
 cinfo.image_width = fb_width(fb);
 cinfo.image_height = fb_height(fb);
 cinfo.input_components = 3;
 cinfo.in_color_space = JCS_RGB;
 jpeg_set_defaults(&cinfo);
 jpeg_set_quality(&cinfo, quality, TRUE);
 jpeg_start_compress(&cinfo, TRUE);
 
 row_stride = fb_width(fb) * 2;
 JSAMPLE* image_buffer = malloc(3 * fb_width(fb));
 
 while (cinfo.next_scanline < cinfo.image_height) 
 {
 int i = 0;
 unsigned short* line = fb->bits + cinfo.next_scanline * fb_width(fb);
 for(i = 0; i < fb_width(fb); i++)
 {
 int offset = i * 3;
 unsigned short color = line[i];
 unsigned char r = ((color >> 11) & 0xff) << 3;
 unsigned char g = ((color >> 5) & 0xff) << 2;
 unsigned char b = (color & 0xff )<< 3;
 image_buffer[offset] = r;
 image_buffer[offset + 1] = g;
 image_buffer[offset + 2] = b;
 }
 
 row_pointer[0] = image_buffer;
 (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
 }
 
 jpeg_finish_compress(&cinfo);
 fclose(outfile);
 
 jpeg_destroy_compress(&cinfo);
 
 return 0;
}

o 主函数

int main(int argc, char* argv[])
{
 struct FB fb = {0};
 const char* filename = NULL;
 const char* fbfilename = NULL;
 
 if(argc != 3)
 { 
 printf("\nusage: %s [jpeg] [framebuffer]\n", argv[0]);
 printf("-----------------------------------------\n");
 printf("Powered by broncho(www.broncho.cn)\n");
 return 0;
 }
 
 filename = argv[1];
 fbfilename = argv[2];
 if (fb_open(&fb, fbfilename) == 0)
 {
 snap(filename, 100, &fb);
 fb_close(&fb);
 }
 
 return 0;
}

完整代码请到这里下载。