The commands in this submenu create, delete or modify selections.
Creates a rectangular selection that is the same size as the image.
Deactivates the selection in the active image.
Restores the previous selection to its original position. A selection is saved when you:
You can transfer a selection from one image to another by activating the image with the selection, activating the destination image, then pressing shift-e (the keyboard shortcut for Restore Selection).
Alternatively you can use the Analyze>Tools>ROI Manager.
Fits a cubic spline curve to a polygon or polyline selection.
Replaces an area selection with the best fit ellipse. The ellipse will have the same area, orientation and centroid as the original selection. The same fitting algorithm is used to measure the major and minor axis lengths and angle when “Fit Ellipse” is selected in Analyze>Set Measurements.
Replaces a polygon of freehand selection with its convex hull, which can be thought of as a rubber band wrapped tightly around the points that define the selection.
When an area selection is active, this commands creates an inverse selection (what was “inside”, now is “outside” the selection).
This command creates a new 8-bit image called Mask whose pixels have value  inside the selection and  outside. By default this image has an inverting LUT (so black is  and white is .
If you choose Process>Binary>Options>Black Background before applyting th4e Create Mask command the inverting LUT is not applied (and so black is  and white is ).
Based on the Threshold_To_Selection plugin contributed by Johannes Schindelin. This command creates a composite selection from a thresholded image or a binary mask.
Issue with ROI closing in versions previous to 1.38b [contributed by A Weller]
In older versions, run(“Create Selection”) does not create a “closed ROI”, which is needed for subsequent plugins like Fourier analysis. Here's a macro solution that subsequently runs the Fourier shape analysis plugin:
run("Create Selection"); // requires 1.37j run("Enlarge...", "enlarge=0"); getSelectionCoordinates(x, y); run("Select None"); // Remove selected ROI makeSelection("polygon", x, y); // Convert selection to what you want, in this case "polygon" run("Fourier ", "fourier=8 output"); // 8 Fourier descriptors with a default curvature of 5
This problem was solved in 1.38b. …
Rotates the selection by the specified number of degrees (negative number indicate counter clockwise rotation). Does not work with composite selections.
Grows the area selection by the specified number of pixels. Enter a negative value to shrink the selection. Enter zero to convert a composite selection into a polygon selection.
Takes an area selection and creates a band with a thickness of the specified number of pixels. If you imagine the band as a doughnut shape, then the original selection corresponds to the hole (i.e. the band is made by growing out the original selection).
This command opend a dialog that allows to define a rectangular area selection.
Width and Height are the dimensions of the selection. X Coordinate and Y Coordinate define the position in the image where the top left corner of the selection will be positioned.
If Oval is checked, this converts the selection into an oval/circle with the same height and width dimensions.
If Centered is checked, the selection is positioned in a way, so X Coordinate and Y Coordinate define the center of the selection otherwise it places places it at the upper left corner at the specified coordinates.
Adds the selection to the ROI Manager (found in Analyze>Tools>ROI Manager…).
The command can also be executed with the Ctrl+T keyboard shortcut.