7.4.2.1   Set up the Measure Task

It is very easy to set up the measure task with the Measure Assistant:

• Choose your Image Source on the Input tab by either using the content of the Graphics Window, loading an Image File, or acquiring the image of an object using the Image Acquisition Assistant.

• Create an ROI using the buttons Draw Line or Draw Circular Arc, which you find in the toolbar of the Measure Assistant. Place the ROI perpendicular to the edges you want to measure.

• Now, that you have located the ROIs, you can extract edges within the chosen region(s) and therefore use the functionality of the Edges tab.

The Input tab offers two more options that you can use if necessary. If you already have calibration data available, you can load the data as described in the paragraph Calibration Source, otherwise just return to the Input tab later. A more advanced feature is changing the mode of the expected gray-value range which is only relevant if your image data uses more than 8 bits. Read more about this topic under Expected Gray Value Range.

In case your edge extraction is not as successful as expected, further improvements can be made using the fuzzy measuring function of the assistant.

Image Source

The Input tab lets you choose images from the following sources:

• If your image has already been opened in the Graphics Window, you can activate Graphics Window to continue working with the currently displayed image.

• You can load an image file by activating Image File or choosing Load Image from the menu File and the tool bar, respectively, and either typing in the image path or using the Browse button on the right to choose an image from a file.

• Another option is to activate the radio button for the Image Acquisition Assistant. Being connected to this assistant, you can acquire the image you want to measure in and you can even choose to work with a Live image. The same operations can be performed by clicking the Snap or Live symbols in the tool bar.

Note that the measuring works on a single channel. For color RGB images, the red channel will be used. A color transformation can be performed with the operator trans_from_rgb.

When you have loaded your image, you can continue to create an ROI. If your image data exceeds 8 bit, you can change the expected gray-value range. If you want to load calibration data or calibrate now, proceed to the section Calibration Source.

Create an ROI

Create an ROI by using the buttons Draw Line or Draw Circular Arc in the tool bar. The shape of the ROI should be chosen according to the shape of the object to be inspected.

After having chosen the ROI shape, you “draw” the ROI in the Graphics Window by keeping the left mouse button pressed. Then, modify the ROI until it has the correct shape. For linear ROIs you can modify the length by “dragging” the line's end points or move it by dragging its center. For circular ROIs you can additionally modify the radius by dragging one of the four circle points that are located at 0, 90, 180, and 270 degrees. When you are finished, click the right mouse button, to confirm your choice. The ROI will already display edges if those can be detected with default parameters.

Remember that the ROI should run perpendicular to the edges you want to measure.

If you have previously prepared and saved an ROI, you can reuse it by choosing Load ROI.

In order to delete one or more ROIs you can either mark them and just press the delete button on your keybord or click the tool bar buttons for Delete Selected ROI Item or Delete All ROIs.

You can view and edit the ROI data, which includes all the data about the exact position of the ROI(s), using the tool bar button View ROI Data. Editing an ROI by changing the ROI data is useful if an ROI should be modified more precisely than is possible by drawing in the graphics window.

When you are satisfied with the shape of your ROI, proceed to the edge extraction on the Edges tab.