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Encode image and copy to char* buffer [closed]

asked 2017-07-06 08:30:46 -0500

minok gravatar image

Hi I would like to copy encoded image as .png to char* buffer. What I am trying is:

CvMat* mat = cvEncodeImage(".png", img, param);
int bufLen = buffer->step;
unsigned char * pData = buffer->data.ptr;
char* buf;
memcpy( buf, pData, bufLen);

However buffer seems to be empty... I am not sure if I am accessing the data the right way, but I am having a hard time finding a proper documentation for this. Also - this has to be done in raw C (it's part of a bigger project).

Has anyone tried to do something like this before?

Cheers

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Closed for the following reason question is not relevant or outdated by berak
close date 2017-07-06 23:10:11.140704

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this has to be done in raw C -- you're too late for that., this is no more an option in 2017.

berak gravatar imageberak ( 2017-07-06 23:09:52 -0500 )edit

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answered 2017-07-06 15:53:25 -0500

matman gravatar image
  1. Don't use C-API. It is deprecated. Use imencode instead.
  2. You try to copy the data to a NULL pointer. You have to allocate required memory first.

Solution could be something like this (from the head):

std::vector<uchar> localBuffer;
imencode(".png", img, localBuffer, param);
char *buf = malloc(localBuffer.size());
memcpy(buf, localBuffer.data(), localBuffer.size());

Don't forget to free buf if you don't need it anymore.

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Asked: 2017-07-06 08:30:46 -0500

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Last updated: Jul 06 '17