User manual

Small Vision System User Manual 55
5.4.3 Rectification Information
bool isRectified; // have we done the rectification already?
bool haveRect; // true if the rectification params exist
svsRectParams rp; // rectification params, if they exist
The images contained in a stereo image object (left, right and left-color) can be rectified, that is,
corrected for intra-image (lens distortions) and inter-image (spatial offset) imperfections. If the images
are rectified, then the variable isRectified will be true.
Rectification takes place in the svsAcquireImage classes, which can produce rectified images
using the rectification parameters. The rectification parameters can be carried along with the stereo
image object, where they are useful in further processing, for example, in converting disparity images into
a 3D point cloud.
If rectification parameters are present, the haveRect variable is true. The rectification parameters
themselves are in the rp variable.
5.4.4 Disparity Image
bool haveDisparity; // have we calculated the disparity yet?
svsDisparityParams dp; // disparity image parameters
short *Disparity(); // returns the disparity image
The disparity image is computed from the stereo image pair by an svsStereoProcess object. It
is an array of short integers (signed, 16 bits) in the same frame size as the input stereo images. The image
size can be found in the ip variable. It is registered with the left stereo image, so that a disparity pixel at
X,Y of the disparity image corresponds to the X,Y pixel of the left input image. Values of –1 and –2
indicate no disparity information is present: -1 is for low-texture areas, and –2 is for disparities that fail
the left/right check.
If the disparity image has been calculated and is present, then haveDisparity is true. The
parameters used to compute the disparity image (number of disparities, horopter offset, and so on) are in
the parameter variable dp.
The disparity image can be retrieved using the Disparity function. This function returns a pointer
to the disparity array, so it is very efficient. User programs should not delete this array, since it is
managed by the stereo object.
5.4.5 3D Point Array
bool have3D; // do we have 3D information?
int numPoints; // number of points actually found
float *X, *Y, *Z; // 3D point arrays
bool *V; // valid 3D point
The 3D point arrays are the 3D points that correspond to each pixel in the left input image. Each
array has the same size (width and height) as the input stereo images. The 3D point array is computed
from the disparity image using the external camera calibration parameters stored in rp. An
svsStereoProcess object must be used to compute it.