Issue with multiple imwrite(".pgm") format in loop

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Are you saving the image with same name in all iterations? It may cause problems if trying to overwrite an existing file. Moreover, why would you want to overwrite a file inside a loop? You'll end up with only the last image

Thank you Lorena for the quick reply. Yes I am overwriting the image in every iteration. It is a limitation with third party application, which access the image with same name and process it.

for ( unsigned int i = 0; i < loops; ++i ) bS = cap.read(frame);

if (!bS) //if not success, break loop
{

    return -1;
}

    /*Grayscale converson*/

cvtColor(frame, gray_image, CV_BGR2GRAY);

imwrite("sample.pgm", gray_image, compression_params);

}

@deepthpk what are you using as compression_params? Have you tried without them? Do you really need them?

I tried compression_params.push_back(CV_IMWRITE_PXM_BINARY); compression_params.push_back(1); both 1 and 0. Doesnt make a difference in crash

Problem is probably in that "push_back". Why don't you just try imwrite("sample.pgm", gray_image); and see if it works? Then if you really need to specify the flags for any reason, we'll work about it

when i removed the compression_params as you mentioned, the program crashed on first iteration itself! imwrite("sample.pgm", gray_image);

opencv_world300.dll!01cf8aa0()  Unknown

Interesting... I guess you've manually compile OpenCV with CMake and enabled the world dll. Are you really using it? I don't know a lot about the dll's, maybe someone else can help here

No, i just took the library as it is. I didnt compile. The error occurs in the function call to opencv_world300.dll. But thanks a lot for looking into this!

But still what do you think the issue can be, if its not the issue about dll. I have extra information: If u save the out file with PNG format,then the crash never happens in any iteration. The issue exists only in PGM format. Unfortunately the thrid party application only takes pgm format.