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The PDT Layers Demo demonstrates two unique capabilities:
lens image while the image outside the lens is known as the
base image. The PDT Layers Demo currently supports PNG, JPG and BMP file formats.
Editing Two Image Layers Simultaneously
The PDT Layers Demo allows you to edit two images at the same time.
In other words, editing one image modifies the second image in exactly the same place.
Editing of the images is accomplished through the toolbar
options which include the Draw curve tool, the Draw line
tool, and the Select region and fill tool.
These tools will be discussed in further detail in the following section.
In this next section we will:
The PDT Layers Demo application window consists of a number of parts:
the main window, the menu bar, the toolbar, and the status bar.
The previous figure illustrates two images within the main window.
The base image is a relief map of the Americas; the lens image
is an elevation view of the same geographic coordinates.
All the modes of interaction for this application are provided through the toolbar or menu options.
Open base image layer button and
the Open lens image layer button located in the toolbar are used to load
images into the main window. These options
are also available under the File menu.
Two steps are required to view two images simultaneously. First,
click on the Open base image layer button to open the image you wish to view
outside the PDT lens. Then click the Open lens image layer
to open the image you wish to view inside the PDT lens.
Both options pop up a dialog box
which allows you to find the files you wish to load.
The base and lens image may be different sizes. However, if the aspect ratio of the two images are different, the lens layer is stretched to match the base layer.
By clicking on the Change lens image button, the image appearing in the
lens can be replaced with the base image. Clicking this button again returns
the original lens image.
This button is particularly useful after using the editing tools
to highlight parts of the image. Instead of moving the lens away
to see where your edits have affected the base layer
simply press the Change lens image
button, or press Ctrl-R. This command fills the lens with
base image layer for magnified inspection. The figures below shows
the effects of pressing the Change Lens Image command.
Activate lens button (if it is not already pressed)
to move and resize the PDT lens within the window.
To explore PDT's viewing capabilities,
try dragging the lens, changing the lens magnification, or folding the lens.
For more information on how to manipulate the PDT lens see Lens basics.
To remove the lens, click on the Remove lens toggle toolbar button.
When the Remove lens icon button is pressed, the icon changes to the
Add lens button icon and vice versa. The PDT lens will reappear
where it was before being removed.
Folding the lens allows you to inspect areas of interest in the
shoulder of the lens without moving the lens. If you cannot clearly see data in the
lens shoulder, fold the lens to extend the shoulder region to make the data
easier to view.
To undo lens folding click on the Remove folding toolbar button.
For more information on what folding is, see Lens basics.
The toolbar provides three tools for editing the image layers. These tools are the
Draw curve, the Draw line, and the Select region and fill tools.
The Draw curve tool can be used to edit individual pixels or
to draw freehand curves.
The Draw line tool creates straight line segments.
The Select region and fill tool creates rectangular
box filled with the currently selected paint colour.
The figure belows shows edits created with the various editing tools.
The circle around the wharf was created with the Draw curve tool;
the arrow pointing to the wharf was made with the Draw line tool;
the rectangular box beside the wharf was generated with the
Select and fill region tool. The process of editing modifies both
image layers.
There are three tools in the toolbar associated with colour selection.
The Pick colour from image provides a means to select a colour by clicking
on a pixel in the base or lens image. The Select colour from dialog button opens
a dialog box for colour selection. The last
tool, Current colour, indicates the currently selected editing colour.
If you edit images and want to "undo" your change, click on the
Undo button provided on the toolbar.
Up to ten sequential undo's are possible.
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