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Convert void buffer pointer to Mat

asked 2016-10-15 11:50:40 -0600

Ralph058
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updated 2016-10-16 00:37:42 -0600

berak
32993 ●7 ●81 ●312

I have a module which receives a void pointer to a buffer. The original data type is uint16.

When I try putting the variable into a Mat, I get weird errors from

Mat imBuff = cv::Mat(628, 314, frame, CV_16U);

like missing '}' which isn't missing.

When I try various conversions using reinterpret_cast, I get cast from 'void*' to 'xxx' loses precision. For example,

 Mat imBuff = cv::Mat(628, 314, reinterpret_cast<uint16_t >(frame), CV_16U);

 fives 'uint126_t' {aka short unsigned int}' loses precision

Any ideas on how to solve this?

Or, do I have to go back to the source file and change it there?

thanks Ralph

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answered 2016-10-15 12:09:29 -0600

berak
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updated 2016-10-15 12:23:04 -0600

i think, you want to use this constructor here

apart from the 3rd arg reserved to the type (CV_16U) , note, that it's (rows,cols) in opencv, not (width,height)

in the end it will be:

void * data_pointer = ...
Mat m = Mat(314, 628, CV_16U, (uchar*)data_pointer);

you'll also have to very cautios here, since this constructor only makes a shallow copy of your data_pointer (no pixels copied). once, your original pointer gets out of scope, anything is invalid, so please take care, you

either stay within the scope of that pointer
or clone() the Mat made from it, and pass that on.

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Thanks.

I think you are correct but I'm still getting a cast error. I'm working on it.

The indexes were correct for the target image because I am using it in the portrait mode. However, the camera system does not know this. In stead of 'clone', I will use 'transpose.'

Ralph058 ( 2016-10-15 16:24:14 -0600 )edit

cv::Mat store it's data in a uchar* pointer, so you'll have to cast to that

berak ( 2016-10-16 00:41:07 -0600 )edit

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Asked: 2016-10-15 11:50:40 -0600

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Last updated: Oct 16 '16

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