Making Image Math Calculations

Use the Calculation command to perform arithmetic and logic calculation upon the active image, sequence, or ROI. Such Calculation can be performed between two images (such as subtracting a “Hi Pass” filtered image from an original image to emphasize high-contrast elements), or between an image and a constant value (such as “ANDing” an image with 240 to retain only the 4 most significant bits of information).

The Calculation command can be used on both monochrome and color images. When applied to a True Color image, the operation will be applied to all three channels. For example, if you were subtracting a value of 10 from the image, 10 would be subtracted from the Red value, from the Green value and from the Blue value in each pixel.

Each image may have one or more ROI.  If neither image has an active ROI, the operation is performed from the upper left corner (position 0, 0) of each image.  If only one image has an active ROI, the operation is performed between that ROI and the corresponding position in the other image.  If both images have an active ROI, the operation is performed on the two ROIs, starting at the upper left corner of the bounding box of each.

If the active image has a multiple ROI, the modifications occur within each ROI.  If the other image has an active multiple ROI, the bounding box for the ROI acts as the ROI for that image.

The Image Math/Calculation feature appears on the Process tab’s ribbon.

To use this feature, follow these steps:

Open two images in the workspace.

From the Process ribbon, click the Calc drop-down arrow. You will see the image calculator.

Using the calculator buttons, decide which image operations you want to perform. In this example, we will add image 1 to image 2 and display the results in a new image.

Click Apply.

The results appear in a combined image.