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Automatic Image Calibration
Charlie Taylor from United States [4 posts] |
7 year
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Hello,
I am trying to run Roborealm on a Kangaroo for a project where I need to identify the specific location of a point in each frame after unwarping the image. However, I am finding that the Automatic Image Calibration (AIC) module (with Intrinsic Transform Only selected) to be too resource intensive. But since I only need to collect the XY from a single pixel in the calibrated image, I'm trying to transform only the single point. However, I am not able to duplicate the calibrated values of selected points using the parameters given by the AIC module.
Specifically, I used the AIC module in version 2.83.10 against a standard checkerboard pattern. It gave me parameters of:
K0=-1019.89 K1=0.0674738
K2=-0.0000591188 KS=998.23
U0=0 V0=0.0732422.
If I let (x,y) represent a point on the raw image and XY represent the exact same point on the unwarped image, my understanding from the documentation for Radial Distortion module and the forum response http://www.roborealm.com/forum/index.php?thread_id=5843 is that I can use the following equations to get (XY) from (xy).
Let X*=x-U0 and Y*=y-V0 then
r=sqrt(X*^2+Y*^2)
z=K0+K1*r+K2*r^2
s-KS/z
and finally X=s * X* and Y=s * Y*.
However, as you can see below this approach is not working. I precisely identified 7 points on the same checkerboard that I used for calibration. My observations and calculated values were:
OBSERVED
x y X Y X Calculated Y Calculated
1180 811 1187 817 1128.536531 775.5597204
1140 248 1148 253 1114.654976 242.4147318
725 298 731 301 721.8199082 296.6199517
720 861 727 867 706.0713252 844.2718011
358 862 364 868 354.6309866 853.8154651
360 502 365 507 359.3362007 501.0012616
360 137 366 141 358.6539781 136.4147955
Clearly my XY observed and my XY calculated are not matching up. I would very much appreciate it if you can help me understand what I am doing wrong here.
Thank you in advance,
Charlie Taylor
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Steven Gentner from United States [1446 posts] |
7 year
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Charlie,
Have you tried just unchecking the [x] Show Calibrated image in that module? That will still convert points that you transform using the variable list but not perform the image transform which makes it significantly faster!
The transform of the image is largely just to show you what things look like calibrated but need not be done to get calibrated points.
STeven.
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Charlie Taylor from United States [1 posts] |
7 year
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Steven,
Thank you for the quick response. I think this approach would work if I could input points from the Point_Location module. For instance, I would like to transform the NW point of a blob image. Is that possible? My "Available variables" window is completely blank.
Thank you very much for your guidance.
Charlie
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Steven Gentner from United States [1446 posts] |
7 year
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Charlie,
Due to the way the interface is, it will only transform arrays that contain X, Y coordinates. Because with a single variable its unknown if its the X or Y coordinate it will only do arrays.
Add a SetVariable module and use
my_points = [NORTHWEST_X], [NORTHWEST_Y] [x] IsArray
that will create a 2 item array that will appear in the AIC module.
Note, this ability to create an array using expressions *JUST* added to the SetVariable module so you will need to download the latest version for this to work.
Options button->Download button.
STeven.
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Charlie Taylor from United States [4 posts] |
7 year
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Steven,
This solution worked very well-- Thank you very much!!
Charlie
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