update images

Author: AleksandrPanov

modules/aruco/tutorials/aruco_calibration/aruco_calibration.markdown

@@ -31,7 +31,7 @@ same way that the standard calibration does with the traditional chessboard patt
 benefits of using ChArUco, occlusions and partial views are allowed, and not all the corners need to be
 visible in all the viewpoints.
 
-![ChArUco calibration viewpoints](images/charucocalibration.png)
+![ChArUco calibration viewpoints](images/charucocalibration.jpg)
 
 The example of using `cv::calibrateCamera()` for cv::aruco::CharucoBoard:
 
@@ -66,7 +66,7 @@ As it has been stated, it is recommended the use of ChAruco boards instead of Ar
 ChArUco corners are more accurate than marker corners. However, in some special cases it must be required to use calibration
 based on ArUco boards. As in the previous case, it requires the detections of an ArUco board from different viewpoints.
 
-![ArUco calibration viewpoints](images/arucocalibration.png)
+![ArUco calibration viewpoints](images/arucocalibration.jpg)
 
 The example of using `cv::calibrateCamera()` for cv::aruco::GridBoard: