How do I make a scale bar to stamp on my images in Openlab?

Technical Note: 10
Reads: 10594
Creation Date: 28/09/1999
Modification Date: 25/07/2005

In Openlab 3.5 or above, a scale bar can be displayed on the image window without creating an annotation layer.

In earlier versions of Openlab, the Paint Tools palette can be used to create any size of scale bar, but it must of course be calibrated to provide an accurate representation of scale in an image. Calibration is achieved by capturing an image of a stage graticule.

View the stage graticule at the same magnification as the image you wish to stamp the scale bar onto, and capture an image. Using the Layers Manager palette, create a new blank image, select this image and drag it to the position above the graticule image in the Layers Manager. Make the background of this new layer transparent by selecting "Transparent Background" from the pop-up menu for that layer. View this layer (place the eye next to it in the Layers Manager). The stage graticule image will be visible through the transparent layer.

Open the Paint Tools palette and select the line drawing tool. Three boxes at the bottom of the palette allow line color, thickness and style to be selected. Chose a color which will show clearly against the background of your image (do not select white for your line color as it will become invisible in the transparent overlay). Chose the line thickness and a line style with no arrowhead.

Using the underlying graticule image as a guide draw a line of the required length.

Select the ROI (Region of Interest) tool from the tool bar on the left side of the image document window. Draw a rectangular region of interest around the newly created scale bar.

Copy this selection - choose "Copy" from the "Edit" menu, or use the keyboard-shortcut, apple c.

In the Paint Tools palette select the stamp tool. Click on the button labelled "Choose". The dialogue opens up to show the list of stamps currently available. Click on the button "Paste new" and the new scale bar will appear in the preview. The stamp should be named in a way that identifies it for future use, for example, with the lens magnification, and camera binning if appropriate. The stamp is now stored for use on any transparent overlay layer to place a scale bar on images.

Note 1: Many stamps can be created not just for different magnifications but also in different colors so that the most appropriate stamp for every image can be used.

Note 2: When drawing the scale bar text may be added to indicate the length of the scale bar. Use the text tool in the paint tools palette. Positioning of this text need not be exact when typing since it is on a transparent overlay, and can easily be selected with an ROI and moved to its final position.