Changes between Version 25 and Version 26 of Tutorial/GeometricCalibration


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Timestamp:
Jan 23, 2015, 1:55:54 PM (6 years ago)
Author:
vaillant1p
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  • Tutorial/GeometricCalibration

    v25 v26  
    77We shall use the diameter of the half cylinder visible on the upper let of the image to set the calibration. Its physical diameter  is 2cm. The corresponding diameter in pixels can be obtained with the ruler displayed by the menu bar '''[Tools/ruler]''' of uvmat.
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    9 First zoom on the cylinder to optimize the precison. Select '''[zoom on]''', press the left mouse button and adjust the field with the directional key board arrows. Then unselect '''[zoom on]''' to allow for other mouse actions (otherwise zoom has priority). It is also useful to increase the contrast at the cylinder edge by setting '''MaxA''' to 100 in the frame '''[Scalar]''' (right side of uvmat).
     9First zoom on the cylinder to optimize the precison. Select '''zoom on''', press the left mouse button and adjust the field with the directional key board arrows. Then unselect '''zoom on''' to allow for other mouse actions (otherwise zoom has priority). It is also useful to increase the contrast at the cylinder edge by setting '''MaxA''' to 100 in the frame '''[Scalar]''' (right side of uvmat).
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    1111Then select the menu bar '''[Tools/ruler]''', press the left hand mouse button on the cylinder edge, draw a diameter keeping the mouse pressed, release it on the opposite edge. The length in pixels, 140, is displayed, so the scaling factor is 140/2=70 pixels/cm.
     
    1313Open the menu bar '''[Tools/geometric calibration]'''. A new GUI '''geometry_calib''' appears on the right side. Activate the upper menu bar '''[!Tools/Set scale]''' on this GUI and introduce the value 70 in the edit box which pops up, and validate with '''[OK]'''. A set of calibration point coordinates appears in the table '''[!ListCoord]''' of the GUI.
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    15 To see the calibration points on the image, first display the whole image by unselecting '''[fix]''' (tag '''[!CheckFixLimits]''') in the frame '''[Axes]''' of '''uvmat'''. Then press '''[PLOT PTS]''' in '''geometry_calib'''.
     15To see the calibration points on the image, first display the whole image by unselecting '''fix''' (tag '''[!CheckFixLimits]''') in the frame '''[Axes]''' of '''uvmat'''. Then press '''[PLOT PTS]''' in '''geometry_calib'''.
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    1717To perform the calibration, press '''[APPLY]''', first with the default option 'rescale' in '''calib_type''', and confirm by pressing '''[OK]''' in the dialog box. The image is now displayed in phys coordinates. A xml file 'images.xml', containing the calibration parameters and reference point coordinates, has been created in the folder 'UVMAT_DEMO01_pair' (it should be identical with the file 'images.ref.xml' put for reference). Note that the xml file name reproduces the name of the folder containing the images, so that images from different cameras should not be put in the same folder.