# Removing blob detector causes frozen appearance

**URL:** <https://forum.opencv.org/t/removing-blob-detector-causes-frozen-appearance/4665>\
**Category:** C++\
**Created:** [August 8, 2021, 6:11pm UTC](https://forum.opencv.org/t/removing-blob-detector-causes-frozen-appearance/4665 "2021-08-08T18:11:52Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![rg0001](https://avatars.discourse-cdn.com/v4/letter/r/9dc877/32.png) [@rg0001](https://forum.opencv.org/u/rg0001)\
**Post date:** [August 8, 2021, 6:11pm UTC](https://forum.opencv.org/t/removing-blob-detector-causes-frozen-appearance/4665/1 "2021-08-08T18:11:52Z")

</div>

So I use the following code without a problem, a simple blob detector routine that appears as video. When I want to remove the blob detector and retain the module, the imshow displays only a single image without “video”; that is, it seems the image doesn’t update. Expected behavior was a single video image without blob detection. How do I get the latter scenario to “update”?

works fine:

```auto
if (typeMode == 2)
				{
					
					Ptr<SimpleBlobDetector> detector = SimpleBlobDetector::create(params); 
					detector->detect(Imageraw, keypoints);
					drawKeypoints(Imageraw, keypoints, imgKeypoints, Scalar(0, 0, 255), DrawMatchesFlags::DRAW_RICH_KEYPOINTS);
					undistort(imgKeypoints, imageUndistorted, cameraIntrinsic, distCoeffs);
					
					imshow("blob detector", imageUndistorted);
					waitKey(0);

				}

```

“Doesn’t work”. Frozen appearance, only imshow/waitKey:

```auto
if (typeMode == 2)
				{
					imshow("no blob detector", imageUndistorted);
					waitKey(1);
}

```

---

<div class="post-metadata">

**Author:** ![crackwitz](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/crackwitz/32/14_2.png) [@crackwitz](https://forum.opencv.org/u/crackwitz)\
**Post date:** [August 8, 2021, 8:57pm UTC](https://forum.opencv.org/t/removing-blob-detector-causes-frozen-appearance/4665/2 "2021-08-08T20:57:36Z")

</div>

that’s not enough code to see what is going on.