CosResult GetSnapshot(const GetSnapshotReq& request, GetSnapshotResp* response);

qcloud_cos::CosConfig config("./config.json");
qcloud_cos::CosAPI cos(config);
GetSnapshotReq req(bucket_name, object_name, local_file);
GetSnapshotResp resp;
req.SetTime(100);
// Set the screenshot width
// req.SetWitdh(xxx);
// Set the screenshot height
// req.SetHeight(xxx);
// Set the format
// req.SetFormat(xxx);
CosResult result = cos.GetSnapshot(req, &resp);
if (result.IsSucc()) {
   // The call is successful. You can call the `resp` member functions to get the return content.
} else {
   // The call failed. You can call the `result` member functions to get the error information.
}