Class CStereoRectifyMap

Defined in File CStereoRectifyMap.h

Class Documentation

class CStereoRectifyMap

Use this class to rectify stereo images if the same distortion maps are reused over and over again. The rectify maps are cached internally and only computed once for the camera parameters. The stereo camera calibration must be supplied in a mrpt::util::TStereoCamera structure (which provides method for loading from a plain text config file) or directly from the parameters of a mrpt::obs::CObservationStereoImages object.

Remember that the rectified images have a different set of intrinsic parameters than the original images, which can be retrieved with getRectifiedImageParams()

Works with grayscale or color images.

Refer to the program stereo-calib-gui for a tool that generates the required stereo camera parameters from a set of stereo images of a checkerboard.

Example of usage with mrpt::obs::CObservationStereoImages:

  CStereoRectifyMap   rectify_map;
  // Set options as desired:
  // rectify_map.setAlpha(...);
  // rectify_map.enableBothCentersCoincide(...);

  while (true) {
    mrpt::obs::CObservationStereoImages::Ptr obs_stereo = ... // Grab stereo
observation from wherever

    // Only once, construct the rectification maps:
    if (!rectify_map.isSet())
      rectify_map.setFromCamParams(*obs_stereo);

    // Rectify in place:
    unmap.rectify(*obs_stereo);
    // Rectified images are now in: obs_stereo->imageLeft &
obs_stereo->imageRight
  }

Read also the tutorial page online: https://www.mrpt.org/Rectifying_stereo_images

See also

CUndistortMap, mrpt::obs::CObservationStereoImages, mrpt::img::TCamera, the application camera-calib for calibrating a camera.

Note

This class provides a uniform wrap over different OpenCV versions. The “alpha” parameter is ignored if built against OpenCV 2.0.X

Rectify map preparation and setting/getting of parameters

inline bool isSet() const: Returns true if setFromCamParams() has been already called, false otherwise. Can be used within loops to determine the first usage of the object and when it needs to be initialized.

void setFromCamParams(const mrpt::img::TStereoCamera &params)

Prepares the mapping from the intrinsic, distortion and relative pose parameters of a stereo camera. Must be called before invoking rectify(). The alpha parameter can be changed with setAlpha() before invoking this method; otherwise, the current rectification maps will be marked as invalid and should be prepared again.

See also

setAlpha()

inline const mrpt::img::TStereoCamera &getCameraParams() const: Returns the camera parameters which were used to generate the distortion map, as passed by the user to setFromCamParams

const mrpt::img::TStereoCamera &getRectifiedImageParams() const

After computing the rectification maps, this method retrieves the calibration parameters of the rectified images (which won’t have any distortion).

Throws:: std::exception – If the rectification maps have not been computed.

const mrpt::img::TCamera &getRectifiedLeftImageParams() const: Just like getRectifiedImageParams() but for the left camera only

const mrpt::img::TCamera &getRectifiedRightImageParams() const: Just like getRectifiedImageParams() but for the right camera only

void setAlpha(double alpha)

Sets the alpha parameter which controls the zoom in/out of the rectified images, such that:

alpha=0 => rectified images are zoom in so that only valid pixels are visible
alpha=1 => rectified images will contain large “black areas” but no pixel from the original image will be lost. Intermediary values leads to intermediary results. Its default value (-1) means auto guess by the OpenCV’s algorithm.

Note

Call this method before building the rectification maps, otherwise they’ll be marked as invalid.

inline double getAlpha() const

Return the alpha parameter

See also

setAlpha

void enableResizeOutput(bool enable, unsigned int target_width = 0, unsigned int target_height = 0): If enabled, the computed maps will rectify images to a size different than their original size.

Note

Call this method before building the rectification maps, otherwise they’ll be marked as invalid.

inline bool isEnabledResizeOutput() const

Returns whether resizing is enabled (default=false)

See also

enableResizeOutput

inline mrpt::img::TImageSize getResizeOutputSize() const

Only when isEnabledResizeOutput() returns true, this gets the target size

See also

enableResizeOutput

inline void setInterpolationMethod(const mrpt::img::TInterpolationMethod interp): Change remap interpolation method (default=Lineal). This parameter can be safely changed at any instant without consequences.

inline mrpt::img::TInterpolationMethod getInterpolationMethod() const

Get the currently selected interpolation method

See also

setInterpolationMethod

void enableBothCentersCoincide(bool enable = true): If enabled (default=false), the principal points in both output images will coincide.

Note

Call this method before building the rectification maps, otherwise they’ll be marked as invalid.

inline bool isEnabledBothCentersCoincide() const

See also

enableBothCentersCoincide

inline const mrpt::math::CQuaternionDouble &getLeftCameraRot() const: After computing the rectification maps, get the rotation applied to the left/right camera so their virtual image plane is the same after rectification

inline const mrpt::math::CQuaternionDouble &getRightCameraRot() const: See getLeftCameraRot()

void setRectifyMaps(const std::vector<float> &left_x, const std::vector<float> &left_y, const std::vector<float> &right_x, const std::vector<float> &right_y): Direct input access to rectify maps. Each map stores float source pixel coordinates, one per output pixel.

void setRectifyMapsFast(std::vector<float> &left_x, std::vector<float> &left_y, std::vector<float> &right_x, std::vector<float> &right_y): Direct input access to rectify maps. This method swaps the vectors so the inputs are no longer available.

Rectify methods

void rectify(const mrpt::img::CImage &in_left_image, const mrpt::img::CImage &in_right_image, mrpt::img::CImage &out_left_image, mrpt::img::CImage &out_right_image) const

Rectify the input image pair and save the result in a different output images - setFromCamParams() must have been set prior to calling this. The previous contents of the output images are completely ignored, but if they are already of the correct size and type, allocation time will be saved. Recall that getRectifiedImageParams() provides you the new intrinsic parameters of these images.

Note

The same image CANNOT be at the same time input and output, in which case an exception will be raised (but see the overloaded version for in-place rectification)

Throws:: std::exception – If the rectification maps have not been computed.

Public Functions

CStereoRectifyMap() = default