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SivamPillai already pointed out that there is a difference between the cvXXX functions that still use IplImage and are part of the C interface of OpenCV and the cv::XXX functions that use cv::Mat as data type and are part of the C++ interface. Whenever you get an error where a function needs a const CvArr* argument, you are probably giving it a cv::Mat instead of an IplImage. I would recommend looking for the C++ equivalent of that function and completely avoiding IplImage as cv::Mat is much more flexible.

About the errors: You seem to be confusing the CvImagePtr types and the OpenCV type cv::Mat. If you want to process the image from the message in OpenCV after you have it copied and encoded in cv_ptr you should assign the data to an actual cv::Mat doing something like

cv::Mat imageColor = cv_ptr->image;

image is the member of CvImagePtr that contains the actual image data. It also contains the header of the image message and the encoding. You don't have to worry about that since the encoding (without the channel order though) is already covered in the type of the cv::Mat.

If you use the above line, you should be able to do something like

std::vector<cv::Mat> channels;
cv::split(imageColor, channels);
// And then if you like
cv::Mat imageB = channels[0];
cv::Mat imageG = channels[1];
cv::Mat imageR = channels[2];

This should give you the separate channels. If you display the with cv::imshow you will see three gray images of course.

You can then apply the threshold function as it is explained here.

SivamPillai already pointed out that there is a difference between the cvXXX functions that still use IplImage and are part of the C interface of OpenCV and the cv::XXX functions that use cv::Mat as data type and are part of the C++ interface. Whenever you get an error where a function needs a const CvArr* argument, you are probably giving it a cv::Mat instead of an IplImage. I would recommend looking for the C++ equivalent of that function and completely avoiding IplImage as cv::Mat is much more flexible.

About the errors: You seem to be confusing the CvImagePtr types and the OpenCV type cv::Mat. (defined in cv_bridge) and cv::Mat (defined in OpenCV). If you want to process the image from contained in the message in OpenCV after you have it copied and encoded in cv_ptr , you should assign the data to an actual cv::Mat doing something like

cv::Mat imageColor = cv_ptr->image;

image is the member of CvImagePtr that contains the actual image data. It also contains the header of the image message and the encoding. You don't have to worry about that since the encoding (without the channel order though) is already covered in the type of the cv::Mat.

If you use the above line, you should be able to do something like

std::vector<cv::Mat> channels;
cv::split(imageColor, channels);
 // And then if you like
cv::Mat imageB = channels[0];
cv::Mat imageG = channels[1];
cv::Mat imageR = channels[2];

This should give you the separate channels. If you display the with cv::imshow you will see three gray images of course.

You can then apply the threshold function as it is explained here.

SivamPillai already pointed out that there is a difference between the cvXXX functions that still use IplImage and are part of the C interface of OpenCV and the cv::XXX functions that use cv::Mat as data type and are part of the C++ interface. Whenever you get an error where a function needs a const CvArr* argument, you are probably giving it a cv::Mat instead of an IplImage. I would recommend looking for the C++ equivalent of that function and completely avoiding IplImage as cv::Mat is much more flexible.

About the errors: You seem to be confusing the CvImagePtr types (defined in cv_bridge) and cv::Mat (defined in OpenCV). If you want to process the image contained in the message after you have it copied and encoded in cv_ptr, you should assign the data to an actual cv::Mat doing something like

cv::Mat imageColor = cv_ptr->image;

image is the member of CvImagePtr that contains the actual image data. data as a cv::Mat. It also contains the header of the image message and the encoding. You don't have to worry about that since the encoding (without the channel order though) is already covered in the type of the cv::Mat.

If you use the above line, you should be able to do something like

std::vector<cv::Mat> channels;
cv::split(imageColor, channels);

// And then if you like
cv::Mat imageB = channels[0];
cv::Mat imageG = channels[1];
cv::Mat imageR = channels[2];

This should give you the separate channels. If you display the with cv::imshow you will see three gray images of course.

You can then apply the threshold function as it is explained here.

SivamPillai already pointed out that there is a difference between the cvXXX functions that still use IplImage and are part of the C interface of OpenCV and the cv::XXX functions that use cv::Mat as data type and are part of the C++ interface. Whenever you get an error where a function needs a const CvArr* argument, you are probably giving it a cv::Mat instead of an IplImage. I would recommend looking for the C++ equivalent of that function and completely avoiding IplImage as cv::Mat is much more flexible.

About the errors: You seem to be confusing the CvImagePtr types (defined in cv_bridge) and cv::Mat (defined in OpenCV). If you want to process the image contained in the message after you have it copied and encoded in cv_ptr, you should assign the data to an actual cv::Mat doing something like

cv::Mat imageColor = cv_ptr->image;

image is the member of CvImagePtr that contains the actual image data as a cv::Mat. It also contains the header of the image message and the encoding. You don't have to worry about that since the encoding (without the channel order though) is already covered in the type of the cv::Mat.

If you use the above line, you should be able to do something like

std::vector<cv::Mat> channels;
cv::split(imageColor, channels);

// And then if you like
cv::Mat imageB = channels[0];
cv::Mat imageG = channels[1];
cv::Mat imageR = channels[2];

This should give you the separate channels. If you display the them with cv::imshow you will see three gray images of course.

You can then apply the threshold function as it is explained here.

SivamPillai already pointed out that there is a difference between the cvXXX functions that still use IplImage and are part of the C interface of OpenCV and the cv::XXX functions that use cv::Mat as data type and are part of the C++ interface. Whenever you get an error where a function needs a const CvArr* argument, you are probably giving it a cv::Mat instead of an IplImage. I would recommend looking for the C++ equivalent of that function and completely avoiding IplImage as cv::Mat is much more flexible.

About the errors: You seem to be confusing the CvImagePtr types (defined in cv_bridge) and cv::Mat (defined in OpenCV). If you want to process the image contained in the message after you have it copied and encoded in cv_ptr, you should assign the data to an actual cv::Mat doing something like

cv::Mat imageColor = cv_ptr->image;

image is the member of CvImagePtr that contains the actual image data as a cv::Mat. It CvImagePtr also contains the header of the image message and the encoding. You don't have to worry about that since the encoding (without the channel order though) is already covered in the type of the cv::Mat.

If you use the above line, you should be able to do something like

std::vector<cv::Mat> channels;
cv::split(imageColor, channels);

// And then if you like
cv::Mat imageB = channels[0];
cv::Mat imageG = channels[1];
cv::Mat imageR = channels[2];

This should give you the separate channels. If you display them with cv::imshow you will see three gray images of course.

You can then apply the threshold function as it is explained here.