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Correcting dead pixels


If one or more pixels remains unchanged in the same place in a series of grabbed images, irresepective of the image being grabbed, the cause could be dead pixels on your camera's CCD. To replace the dead pixels on newly grabbed images with an average pixel value, taken from the neighboring pixels, use MimDeadPixelCorrection(). This function uses a dead-pixel image processing context to store processing settings.

You can list the coordinates of the dead pixels, using MimPut() with M_XY_DEAD_PIXELS and two arrays (the first containing the x-coordinates, and the second containing the y-coordinates). Alternatively, create a MIL image buffer to act as a mask, where all non-zero pixels are considered dead pixels. Once specified, the coordinates of the non-zero pixels can be inquired, using MimGet() with M_XY_DEAD_PIXELS.

MimDeadPixelCorrection() replaces dead pixels with an average of their non-dead pixel neighbors. Other pixels are copied from the source image buffer into the destination image buffer unchanged. The source and destination image buffer must be as large (or larger than) the dead pixel mask or equal to or larger than the largest dead pixel position of the array containing the x- and y-coordinates of the dead pixels for the source and destination, respectively.

If the dead pixel mask is smaller than the source image, dead pixels on the edge of the intersection of the mask, the source image, and the destination image will only use neighboring pixels that are inside the intersection of the images when calculating the correction. Dead pixels outside the intersection are ignored.

Preprocess the image processing context by calling MimDeadPixelCorrection() with M_PREPROCESS. Both the source and destination image buffers can be set to M_NULL. If, however, the source or destination image is provided, it should be a typical source or destination buffer, respectively, and it will be used in the preprocess operation, to better optimize future calls to MimDeadPixelCorrection(). If the preprocess operation was not done explictly (using M_PREPROCESS), it will be done when MimDeadPixelCorrection() is first called.