![]() ![]() Contrast andīrightness adjustment, called contrast enhancement, is easilyĪpplied to Viking images to improve the visibility of specificįeatures of scientific interest, often with impressive results. Most important are the brightness and contrast. The quality of an image is affected by many things, but probably the Note that, in 035A72, there are no reseaus near the "face,"īut that in 070A13, there is a reseau on it. Figure 2 bottom (left and right) shows the effect of removing ![]() Similar to that used to remove bit-errors, but covering more than one They may also be removed for cosmetic purposes, using a technique Reseaus or reseaux, can be used to correct for camera. Small dots painted on their face-plates at regular intervals, which Might be encountered in space after launch, the Viking vidicons had If one holds a magnet near a TV tube, one sees largeĭistortions of the image. "read" by the change in current of an electron beam scanned across the Surface proportional to the amount of light falling on it, and is (which is how a TV tube works), charge builds up on a vidicon's The strength of an electron beam shot at a phosphorescent surface Rather than emitting light proportional to These tubes operate much like a CRT or television The Viking Orbiter cameras used vidicon television tubes to acquire These images were contrast enhanced so the effects of processing could Right) illustrate the application of this technique.įigure 2: Bit-error corrected (top) and reseau-removal (bottom) The differencesīetween Figure 1 bottom (left and right) and Figure 2 top (left and Value with the average of its nearest neighbors. Means to radically improve the appearance of an image is to replaceĪny value that differs from its neighbors by more than a specified A relatively simple but remarkably effective Resulting incorrect picture elements were less easily distinguishedįrom correct picture. Other times these random errors were in the low bits, and the SometimesĮrrors were in the high bits, resulting in bright or dark pixels at As a result, randomĮrrors were introduced into the data stream as bit errors. NASA's Deep Space Network antennas in California, Spain, and Australiaĭid not incorporate error-correcting encoding. The communications link between the Viking Orbiter spacecraft and Those that were enlarged using bicubicįigure 1: Raw (top) and contrast-enhanced raw (bottom)Įnlargements of 035A72 (left) and 070A13 (right). The same value for each 3 X 3 area in the enlargement) was used for Pixel-replication (i.e., taking each pixel and using ![]() These figures the images have been enlarged by a factor of 3 forīetter viewing. With the best two images of the "Face"(Figure 1). In the figures below, the generalįlow of processing for Viking Orbiter data is outlined, illustrated One advantage of digital imaging is the ability to process the data in
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