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Background normalization serves for unifying colors.
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Blur
This function blurs the picture and reduces noise. Details in the OpenCV documentation.
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This function lets you adjust the gamma value.
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Camera calibration
This function can be used to remove some camera-related distortions of the image.
It uses a calibration pattern, which needs to be photographed by the camera that we are going to use for inspection and at the position where the inspected objects will be. This pattern can be downloaded from the OpenCV website and then printed out to place it to the inspection site. When we make a photo of this pattern with our camera, we select it as the template image and then all images will be transformed in the same way.
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The Calibration subfunction removes the “fisheye” effect (straight lines of the pattern look curved outwards to the edges of the image), the result of the transformation on our sample image looks like this:
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The Perspective transform performs a transformation of the image in a way that the pattern will end up looking as if it's placed perpendicular to the camera (correction for situations where the inspection plane is somehow tilted in relation to the camera).
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Kernel size
Some transformations use a parameter called ‘Kernel size’, which determines the size of the matrix of surrounding pixels, which are taken into consideration when computing the transformation.
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