Image Processing Output Image The output image is the image resulting from an image processing operation. l The user can specify the type of output images as either unsigned 8-bit, signed 16-bit, or signed 32-bit images. l ACE Sight processes other than the Image Processing Tool can only take unsigned 8- bit images as input. Arithmetic Operations Arithmetic operations are performed by promoting the input values of the source pixels (from the Input image) and the Operand values to the highest resolution of the Input Image, Oper- and image or desired output image type. The results of the operation are converted according to the following rules:
l Destination pixel value = ClipMode (Result * Scale) l Destination pixel value is truncated as necessary Clipping Modes Two clipping modes are available for arithmetic operations: normal and absolute. Normal Clipping Mode Normal Clipping mode forces the value of a destination pixel to a value from 0 to 255 for unsigned 8-bit images, to a value from -327678 to 32767 for signed 16-bit images, or to a value from -2,147,483,648 to 2,147,483,647 for signed 32-bit images. Values that are less than the specified minimum value are set to the minimum value. Values greater than the specified maximum value are set to the maximum value.
Absolute Clipping Mode The absolute clipping mode takes the absolute value of the result and clips it using the same algorithm as for Normal Clipping mode. Arithmetic Operation Modes There are two Arithmetic operation modes. In the first, the operation is applied to every pixel of an input image and the corresponding pixel in the Operand image. The result is written in the output image. In the second mode, the operand is a constant, and it is used on every pixel of the input image and the result is written in the output image. The Image Processing Tool supports the following arithmetic operations: Addition, Sub- traction, Multiplication, Division, Lightest and Darkest.
ACEUser's Guide, 3.6.x, 18316-000 Rev A Page 510