Reconstruction of Proper Constitution

We are processing noisy data. Thus, intensities may have become negative by accident. In order to mark such spots as invalid data, they should be set to zero. This is accomplished by the masking formalism of image processing 

The first line generates the mask of the still valid pixels, the second pulls the invalid pixels to zero level. The example works in pv-wave and IDL, if img.map is the map of the image. 

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