xcb 截图

1xcb_get_image_cookie_t
2xcb_get_image (xcb_connection_t *c,               // X连接
3               uint8_t           format,          // 格式 
4               xcb_drawable_t    drawable,        // 要截图的目标，例如窗口，截全屏则为 root 窗口
5               int16_t           x,               // 截图的起点 x 坐标
6               int16_t           y,               // 截图的起点 y 坐标
7               uint16_t          width,           // 截图的宽度
8               uint16_t          height,          // 截图的高度
9               uint32_t          plane_mask);     // 色彩通道掩码，例如 0x00ff0000 表示只保留红色通道（小端）

1#include <xcb/xcb.h>
2#include <stdio.h>
3#include <stdlib.h>
4
5// 将 BGRX 转换为 RGB
6static uint8_t* BGRX2RGB(const uint8_t* in, int16_t width, int32_t height)
7{
8    uint8_t* out = malloc(width * height *3);
9    for (int16_t y = 0; y < height; y++)
10    {
11        for(int16_t x = 0; x < width; x++)
12        {
13            out[(y*width+x)*3] = in[(y*width+x)*4 + 2];
14            out[(y*width+x)*3 + 1] = in[(y*width+x)*4 + 1];
15            out[(y*width+x)*3 + 2] = in[(y*width+x)*4];
16        }
17    }
18    return out;
19}
20
21int main()
22{
23    // 建立连接
24    xcb_connection_t* conn = xcb_connect(NULL, NULL);
25
26    // 获取 screen
27    const xcb_setup_t* setup = xcb_get_setup(conn);
28    xcb_screen_iterator_t iter = xcb_setup_roots_iterator(setup);
29    xcb_screen_t* screen = iter.data;
30
31    // 获取 root 窗口
32    xcb_window_t root = screen->root;
33
34    // 获取屏幕的宽高
35    int16_t width = 0;
36    int16_t height = 0;
37    {
38        xcb_get_geometry_cookie_t cookie = xcb_get_geometry(conn, root);
39        xcb_get_geometry_reply_t* reply = xcb_get_geometry_reply(conn, cookie, NULL);
40        width = reply->width;
41        height = reply->height;
42        free(reply);
43    }
44
45    // 读取屏幕图像
46    uint8_t* data = NULL;
47    {
48        // XCB_IMAGE_FORMAT_Z_PIXMAP 是 BGRX 格式
49        // 其中 plane_mask 用于过滤不需要的通道,例如 0x00ff0000 表示只保留红色通道（注意小端）
50        xcb_get_image_cookie_t cookie = xcb_get_image(conn, XCB_IMAGE_FORMAT_Z_PIXMAP, root, 0, 0, width, height, UINT32_MAX);
51        xcb_get_image_reply_t* reply = xcb_get_image_reply(conn, cookie, NULL);
52        data = BGRX2RGB(xcb_get_image_data(reply), width, height);
53        free(reply);
54    }
55
56    FILE* fp = fopen("out.ppm", "wb");
57    fprintf(fp, "P6\n");
58    fprintf(fp, "%d %d 255\n", width, height);
59    fwrite(data, width*height*3, 1, fp);
60    fclose(fp);
61
62    free(data);
63    xcb_disconnect(conn);
64
65    return EXIT_SUCCESS;
66}