Return Mat_<float> data not uchar

asked 2018-03-28 13:23:27 -0600

jasonalh
1 ●1

I'm refactoring some code from cimg to opencv. I have the following lines that should return Mat_<float>.data.

  // Get a pointer to the data.
  //  T* Data() { return image_.data(); } <-cimg calls
  //  const T* Data() const { return image_.data(); } <-cimg.calls
  T* Data() { return image_.data; }
  const T* Data() const { return image_.data; }

but I get a compile error:

error: cannot initialize return object of type 'float *' with an lvalue of type 'uchar *' (aka 'unsigned char *')
  T* Data() { return image_.data; }

Other part of the code:

      cv::Mat_<T> image_;
   ... 
      image_ = cv::imread(filename.c_str(), CV_LOAD_IMAGE_ANYCOLOR | CV_LOAD_IMAGE_ANYDEPTH);

From what I've read Mat.data is of type uchar. But shouldn't data be float when I use Mat_<float>?

Thanks, Jason

edit retag flag offensive close merge delete

Comments

CV_LOAD_IMAGE_ANYCOLOR | CV_LOAD_IMAGE_ANYDEPTH -- that's one of the few situations with opencv, where you cannot estimate the type at compile time.

thus you cannot use "typed" template Mat's here.

reconsider your design.

berak ( 2018-03-28 13:28:41 -0600 )edit

Ok, then I should use cv::imread(filename.c_str(), CV_LOAD_IMAGE_COLOR) But are you also saying that cv::Mat_<T> image_ will not be loaded as a float when imread is called?

jasonalh ( 2018-03-28 13:45:57 -0600 )edit

cv::imread(filename.c_str(), CV_LOAD_IMAGE_COLOR) would return CV_8UC3 data, uchar, not float.

again why do you insist on using Mat_<float> (or any templated version ?)

berak ( 2018-03-28 13:51:53 -0600 )edit

This is an older code base and the main class/object is built on templates.

// Templated on the number of channels.
template <typename T> class Image {

jasonalh ( 2018-03-28 13:59:07 -0600 )edit

maybe that's a bad idea. cv::Mat is NOT a template class by default

berak ( 2018-03-28 14:04:10 -0600 )edit

Well that's unfortunate. Isn't that what cv::Mat_<T> is for? To handle template classes.

jasonalh ( 2018-03-28 14:06:43 -0600 )edit

"Isn't that what cv::Mat_<T>is for?" sure.

again, in 90% of all cases you know the type offhand.

but you can't use templates, if the type changes / is determined at runtime

berak ( 2018-03-28 14:09:12 -0600 )edit

add a comment

cv::Mat matInputUnknownType = cv::imread("..."); int matType = matInputUnknownType.type(); if (matType == CV_8UC1) { cv::Mat1b mat = matInputUnknownType; // use it } if (matType == CV_8UC3) { cv::Mat3b mat = matInputUnknownType; // use it } if (matType == CV_8UC1) { cv::Mat4b mat = matInputUnknownType; // use it }

cv::Mat3b matInput; cv::Mat matTemp = cv::imread("..."); switch (matTemp.type()) { case CV_8UC1: cv::cvtColor(matTemp, matInput, CV_GRAY2BGR); break; case CV_8UC3: matInput = matTemp; break; case CV_8UC4: ... default: dance(); }

Return Mat_<float> data not uchar

Comments

1 answer

Links

Question Tools

Stats

Related questions

Return Mat_<float> data not uchar edit

Comments

1 answer

Links

Question Tools

Stats

Related questions

Return Mat_<float> data not uchar