Transfer Selection

The Transfer Selection command allows transfer of a selection from one component in a map to another. It is most frequently used to select pixels in an image that are within a selection made in a drawing or vice versa. The Transfer Selection command appears in the context menu when right clicking on a layer tab or in the main menu for that component in the main menu bar. It may be used to transfer selections between drawings, images, surfaces and labels in any combination.

To transfer a selection from layer A to layer B:

1. Create a map that shows layer A and layer B together.

2. Right-click on the layer B tab and choose Transfer Selection.

3. In the Transfer Selection dialog, ensure that the checkbox for layer A is checked and the boxes for other layers (if any) are not checked.

4. Press OK.

The Transfer Selection command will transfer the selection from all checked layers to the target layer specified in the dialog's Modify box. For example, if an area is selected in a drawing layer and the selection is transferred to an image in the map all pixels in the image that fall within the selected area will also be selected.

When used to transfer selections to objects, the Transfer Selection command will select any object that touches (that is, when any part of the object falls within) an existing selection. Pixels are selected if the center of the pixel falls within a selected object.

Controls

	Modify	Transfer the selection to this component. Will be loaded by default with the name of the component whose layer was right-clicked to call up the context menu.
$images\btn_layer_show_all.gif$	Select All	Use all layers in the map.
$images\btn_layer_hide_all.gif$	Select None	Do not use any layers in the map.
$images\btn_layer_invert_all.gif$	Select Inverse	Check those layers not currently checked and un-check those currently checked.
	Using	Transfer the selection in the checked layers to the layer in the Modify box.

Example

This example transfers a selection from objects in a drawing to pixels in an image.

$images\eg_transfer_selection_01.gif$

We have a map that contains an image called Australia Image and a drawing called Australia and Oceania that shows boundaries.

$images\eg_transfer_selection_02.gif$

We add a drawing called Circles in which we create some circular areas. The areas are shown in blue in the illustration above using a 50% Layer Opacity value.

$images\eg_transfer_selection_03.gif$

We select one of the circular areas using touch selection. We would like to transfer this selection to the image so that all pixels that lie within this selected circular area are selected in the image.

$images\eg_transfer_selection_04.gif$

We right-click on the Australia Image layer tab and choose Transfer Selection. In the Transfer Selection dialog we check the Circles box since we only wish to transfer the selection from that layer and not from the other drawing. Press OK.

$images\eg_transfer_selection_05.gif$

If we turn off the Circles layer in the map we can see that the pixels in the Australia Image layer that lay within the selected circle are now selected.

Example

The previous example transferred a selection from objects in a drawing to pixels in an image. This example shows the opposite situation, where a selection in pixels is transferred to objects in a drawing.

$images\eg_transfer_selection_06.gif$

Suppose we select the pixels of the darker region in the image as seen above. The selection was made quickly using touch selection and Add to Selection mode. Note that not all pixels in the region of interest have been selected. For our purposes it will not matter that all pixels in the region of interest have not been selected.

$images\eg_transfer_selection_07.gif$

We now wish to select those objects in the Circles drawing layer that touch any of the selected pixels. To do so, we right click on the Circles layer tab and choose Transfer Selection. Note that it does not matter that all of the pixels in the region of interest have not been selected since the size of the circles is such that some selected pixels will be in each of the circles.

$images\eg_transfer_selection_08.gif$

In the Transfer Selection dialog we check the Australia Image box to transfer the selection from that layer to the Circles layer.

$images\eg_transfer_selection_09.gif$

The result is that all four circular areas that touch any of the selected pixels are selected.

Notes

To transfer selections between components the components must appear together in the same map. If the components are not correctly georegistered and so do not appear correctly aligned in the map then the selection transfer process cannot function.

The examples show transfers between area objects in drawings and pixels in images. Other objects, such as lines and points, can also be used. For example, a frequently used technique to extract information from raster images or surfaces into vector form is to create a fine grid of points in a drawing, select certain pixels in an image and then transfer the selection to the grid of points. The drawing's table can then be opened and a value assigned within some field for all of the selected points.