为了截几张图片给idcfree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 idcfree()\n”);return 0;}
filename = argv[1];fbfilename = argv[2];if (fb_open(&fb, fbfilename) == 0){snap(filename, 100, &fb);fb_close(&fb);}
return 0;}
人生就像是一场旅行，遇到的既有感人的，
