Create Annotations

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Lesson content

Lesson 1 of 1

Create Annotations

This quick guide demonstrates how to set annotation preferences, add annotations, and manage annotation layers.

Open an Image

1

Select File > Open from the Menu bar. An Open dialog appears. 2. 2

When the Open dialog appears, go to the "data" directory in your ENVI installation path.

Windows: C:\Program Files\NV5\ENVIxx\data (xx is the version number)
Linux: /user/local/NV5/envixx/data
Mac: /Applications/NV5/envixx/data 3. 3

Select the file qb_boulder_msiand click Open. This is a QuickBird multispectral image of Boulder, Colorado. The picture below shows the image at its full extent.

Set Annotation Preferences

You can use the Preferences dialog to define annotation properties before adding them to the Image window. This is suggested if you will be adding several annotations at once. Properties include text font, line colors and width, symbols, and many more. These preferences immediately take effect on all subsequent actions without requiring you to restart ENVI.

1

Select File > Preferences from the Menu bar. The Preferences dialog appears. 2. 2

Expand the Annotations folder on the left side of the dialog to see the different annotation types included in ENVI. 3. 3

Select Symbol and notice the various properties you can set for symbols.

4

Click inside of the Symbol Character field. A popup window appears with different symbols to choose from. 2. 5

Select the building with a flag, as shown below. Then click OK.

6

Set the Scale on Zoom property to Yes. When you zoom in or out of the image, the symbol's size will remain the same. 2. 7

Set the Font Size property to 24. 3. 8

Click the Text item on the left side of the Preferences dialog, then set these properties:

Font Size: 18
Scale on Zoom: Yes

9

Click the Polyline item. 2. 10

Click inside of the Line Color field and click the small arrow that appears. A Select Color dialog appears.

11

Choose any shade of red. The Select Color dialog is dismissed. 2. 12

Set the Line Thickness property to 4. 3. 13

Click OK to dismiss the Preferences dialog. Next, you will add some annotations to the image.

Add Annotations

1

Zoom in to the large, white school to the left of the lake.

Tip: Rotate the scroll wheel on your mouse to zoom in and out of the image. Click and hold the middle mouse button or scroll wheel to pan around the image.

2

Click the Annotations drop-down list in the Toolbar and select Symbol.

The cursor changes to a crosshair symbol.

3

Click on the school to add a symbol. The symbol is surrounded by a blue border to indicate that it is active. 2. 4

Move the symbol to a preferred location, then press the Esc key on your keyboard. This deselects the symbol and sets it in place. The Layer Manager contains a "New Annotation" layer with one "Symbol" item.

5

Click the Annotations drop-down list in the Toolbar, and select Text. 2. 6

Click near the school. A vertical yellow line appears. 3. 7

Type School, then press the Esc key. A blue border surrounds the text. 4. 8

Move the text to a preferred location, then press the Esc key again to deselect it. A new "Text" item is added to the "New Annotation" layer in the Layer Manager.

9

Zoom out of the image and notice how the annotations zoom out accordingly. This is because you set the Scale on Zoom property to Yes on both annotation types in the Preferences dialog.

10

Select the Text item in the Layer Manager. The "School" text is surrounded by a blue border. This is how you select annotation items if you want to change their properties or move them around. 2. 11

The Property Sheet in the lower-right corner of the ENVI application displays the properties of the text annotation. You can change these as needed, which will override any preferences that you previously set. Any changes you make only apply to the annotation selected.

12

Click the Annotations drop-down list in the Toolbar, and select Polyline. 2. 13

Click on one end of a road. A red line extends from that point. 3. 14

Click on a different point along the road, then right-click and select Accept. This completes the polyline.

Here are some other tips for working with annotations:

•

If you use another navigation tool in the Toolbar (such as Pan, Zoom, Rotate, etc.), any annotations that you were working with lose focus. To resume work, click the Select button (the arrow) in the Toolbarand select the appropriate annotation item in the Layer Manager. A blue border surrounds the annotation to indicate that it is active. * •

To delete an annotation item, select it in the Layer Manager and press the Del key on your keyboard. Or, right-click on the item in the Layer Manager and select Delete.

Next, you will create a second annotation layer and add Image Magnifier annotations to the image.

Add Image Magnifier Annotations

You can create different annotation layers in the Layer Manager to organize your annotations into distinct groups. If you add dozens of annotations to one layer, you will have a difficult time keeping track of individual items in a long list. For this exercise, you will create a new annotation layer with two Image Magnifier items.

1

From the Menu bar, select File > New > Annotation Layer. A Create New Annotation Layer dialog appears. 2. 2

Change the Layer Name to Magnifiers. 3. 3

Click OK. A new "Magnifier" annotation layer is added to the Layer Manager.

4

Click the Annotations drop-down list in the Toolbar and select Image Magnifier. 2. 5

Zoom into the image and find a feature that looks interesting, such as a building or tennis court. 3. 6

Click and hold down the left mouse button and then draw a box around the feature. Release the left mouse button to complete the box.

A yellow line extends from the box to a new square with blue-colored handles. That square is the image magnifier. It is relatively small at this zoom level.

7

Press the F12 key to zoom to the full extent of the image. 2. 8

Click and drag the upper-right corner of the image magnifier to expand its size. 3. 9

Hover the mouse over the image magnifier until the cursor changes to four arrows, then move the image magnifier to a preferred location.

Here is a quick video demonstration of these steps.

7

In the Property Sheet, notice that the Zoom Factor value changes as you expand the box.

8

Press the Esc key to deselect the annotation. 2. 9

Click the Annotations drop-down list again and select Image Magnifier. 3. 10

Zoom into the image and draw a box around another small feature of interest. 4. 11

Resize and move the image magnifier as needed; for example:

12

Press the Esc key to deselect and complete the second image magnifier. The Layer Manager lists two "Image Magnifier" items under the "Magnifiers" folder.

Save Annotations to Disk

A suggested practice is to save annotation layers so that you can display them with the same image in a future ENVI session.

1

In the Layer Manager, right-click on Magnifiers and select Save As. A Save As dialog appears. 2. 2

Navigate to a preferred output directory, and name the file Magnifiers.anz. 3. 3

Click Save. 4. 4

In the Layer Manager, right-click on New Annotation and select Rename Item. 5. 5

Change the name to Basic Annotations and press the Enter key. 6. 6

Right-click on Basic Annotations and select Save As. 7. 7

Name the annotation file Basic Annotations.anz and click Save.

This concludes the exercise. You learned how to work with basic annotation types such as symbols, text, polylines, and Image Magnifiers. Other basic types such as Polygon, Ellipse, Rectangle, and Arrow work similarly.

Other annotation types can be used in special cases:

•

Use Legend annotations with ENVI classification images. * •

Use Color Bar annotations with images that have a color table applied. * •

Use Picture annotations to add pictures to an image. Examples include JPEG, GIF, PNG, or any other raster format that ENVI supports. * •

Use Range Ring annotations to draw a single circle, or multiple concentric circles, around a given point. You can define the distance (radius) of each point to the circle(s). * •

Use Scale Bar and Grid Lines annotations in map presentations. See the Create Map Presentations quick guide for more information.

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