Question

A Look-Up Table used to convert pixel values to output values on a monitor. Essentially, all pixels with a value of 190 or above are shown as white (i.e. 255), and all values with a value of 63 or less are shown as black (i.e. 0). In between the pixels are scaled so that a pixel with a value P is converted to a pixel of value 2/127 (?2−126?+3969).
If a pixel has a value of 170 originally, what value will be used to display the pixel on the monitor? If a value of 110 is used to display the pixel on the monitor, what was the original value of the pixel?

Answer 1

The value of pixel p originally is equal to 170

2 (1702- 126(170)3969) 127 |Display value of this Pixel 180.29

Nearest Integer answer will be 180

Hence the value of 180 will be used to display the pixel on the monitor

Now, in the second part of the problem, we need to equate the equation to 110 and calculate the value of p

110 = (p2- 126p 3969) 127

p126p 3969) 6985

2 - 126p 3016 = 0

Solving the quadratic equation we get

p 63 6985, 63 V6985

The second value is not possible since the pixel range is only from 0 to 255

p 63 6985 146.57

Hence the original value of pixel will be 147 (rounded to nearest integer)

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