TILLvisION Tutorial

TILLvisION - Palettes

The IMAGO CCD Camera provides a genuine 12-bit dynamic. For display purposes these 12 bits need to be reduced to 8 bit. Images without palettes are displayed with the default bitshift (menu: Tools/Options/General).

	The bitshift scales the intensities between 0 and (2 bitshift -1 -1). To increase the visible dynamic it is normally useful to autoscale the image. After that the gray value display is scaled between the lowest (displayed as black) and the highest existing intensity (displayed as white). The image intensities are mapped through a Mapping Palette.
	Because the average human eye can only distinguish between about 64 levels of gray, it is useful to display intensities miscolored. This is done in TILLvisION by attaching a so-called Display Palette to the image.

A more technical view

For most experiments, the mathematics involved in displaying images is irrelevant. But if you are interested in effects like combining the information of two images - as described in TILLvisION - Image combination - it is useful to have a better understanding of the details.

The display process starts with the intensity of a pixel out of the image WL 340. For your convenience the intensities along a line are shown in the Line Profile below the image. For every pixel the intensity is used as index into the mapping palette Map16x8b. The resulting value is used as index into the Display Palette. From there every single intensity gets three color values out of RGB. The color bar shown at the right (and below) of the Display Palette is formed out of the combination of these colors.

What You See Is What You Need

The resulting image view in TILLvisION is shown left. All information involved with the display process is visible. The values in the colored bar on the right (the Scale) indicate the scaling (the mapping process). The colors come from the Display Palette of the image.