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Hi, i am having trouble inveting an 3x2 Transformation Matrix. If my original transformation is rotation with +5°, i want the inverse, which rotation is -5°. Then i want to transform some point with the new inverse Matrix. If I use

    cv::Mat inverse;
    inverse = H.inv(cv::DECOMP_SVD);

I get back a matrxi, but it is 2x3 instead of 3x2, and then i cannt use cv::transform anymore because it gets a SIGABRT.

What am i doing wrong ?

regard Peter

thanks for the answers. Yes we are using Keypoints to get the transformation. So you mean i have the transformation from Image A to B, then I take the Keypoint from image B, transform it with the Inverse Matrix and then compare it to the Keypoints i got in Image A ?

Hi,

i am using OpenCV to calculate a transformation (Rotation + Translation) between two 2D greyscale (pgm) pictures. Now we are looking for a way to calculate how good the transformation we got is. Is there something available in OpenCV to rate the resulting transformation matrix ? Or does somebody know some algorithm to achive this ?

Hi,

i use estimateRigidTransform, in most cases it works, but sometimes it return a 0 scaleX/Y and transX/Y. Thats my code to calce the values.

Mat M = estimateRigid(...);

transx = M.at<double>(0,2);

transy = M.at<double>(1,2);

scalex = sqrt(pow(M.at<double>(0,0),2)+pow(M.at<double>(0,1),2));

scaley = sqrt(pow(M.at<double>(1,0),2)+pow(M.at<double>(1,1),2));

what doues it mean if the method returns all 0 ? I thought if it find no transfrom the Matrix is empty.

Hi,

i have got a 2x3 transformation matrix, and have already calculated translationX/Y scaleX/Y and rotation, but i also need do calculate the shear of the matrix, does any one know how to extract it ? All i found in on the internet just looks at the other 5 values.

Hi,

i would like to know how to read the information of a 2x3 Transformation Matrix. If i am right, it contains the rotation, the translation x/y and the scale x/y. But what is the sixth value used for ?

I need to read the rotation from the matrix in RAD or DEG.

I hope someone can explain me the 2x3 Transformation Matrix a little more detailed.

hope it is now more understandable

Hi, i have accomplished to use openCV in ROS.

I have installed opencv [https://help.ubuntu.com/community/OpenCV],not sure if it is necesarry i had it on the pc before i intalled ros.

The vision_opencv is a "bridge" to use opencv with ros, for further information look http://www.ros.org/wiki/vision_opencv and http://www.ros.org/wiki/opencv2

And of course you need to tell ros that the package needs opencv to run/compile. So you need to include it into your CMakeList.txt (here i mean the CMakeList.txt in your package):

find_package(OpenCV REQUIRED)

target_link_libaries(your_node ${OpenCV_LIBS})

your_node is just a placeholder, there should be the name of your library or execution. If you are not so familiar with CMake, read on http://cmake.org/cmake/help/v2.8.8/cmake.html about the target_link_libaries/find_package macro. And you need to create a dependenc in your manifest.xml

<rosdep name="opencv2"/>

hope that helps you

Hi, what flags do i need by cv::warpAffine to do no interpolation ? Or is there a way to mark the "outliners" in a special color ?

Hi,

how can I transform a Coordinate (X/Y) with a 3x2 Transform Matrix?

For example, I have an image (img1) of 2048x2048 px, transform it (apply some rotation and translation) and then get img2. Now I want to know, where the pixel, which was at the point P(100/150) in img1, is in img2?

It does not have to be totally accurate, some pixels off is no problem. Is there any method to achieve this in OpenCV ?