# Lookup Table

A lookup table is an n-element array corresponding to the pixel values 0 through n, where array element [0] corresponds to grey value 0, element [1] corresponds to grey value 1, and so on until element [n] which corresponds to the highest grey value n in your images.

If your acquisition device supports a Lookup Table tab, you can access the array of grey values assigned to your acquired images. The following figure shows the default Lookup Table tab:

An acquisition channel using a lookup table evaluates each pixel in the image buffer and changes the grey value based upon the value for the corresponding element in the array. For example, if table element [50] has the value 75, any pixel with a grey value of 50 is given the new grey value of 75 before the image is made available for analysis by any other vision tool.

Click inside the Value cell to change the value of any incoming grey value. Click Invert to swap dark values for light value and light values for dark values. Click Reset to set all values to their identity defaults.