Automatic measurement of leaf area

• Open image file leaves.png, which is present in the Digimizer\Sample Images subfolder in the My Documents folder.
• Select Contrast autofix in the Image menu. This will automatically maximize the contrast in the image.

  

• The image contains a ruler which we will use to calibrate our measurements.
• Select the Zoom in tool.

  

• Drag a rectangle over the ruler so it is enlarged.
• Select the Unit tool.

  

• Click on the small vertical line above the value 0 and next click on the line above the value 10.

  

• A dialog box is displayed in which we enter the real length of the unit line: 10 cm.

  

• Click the Zoom to fit tool.

  

• Select Binarization in the Binary menu. The following dialog box is displayed:

  

• The dialog box displays a histogram of gray levels. A red line indicates the default threshold value.
• Click Preview. All gray levels below the threshold value will become red (indicating an object), those above white (indicating background).
• Click OK to accept the threshold value.

  

• Select Analyze Objects in the Binary menu. Complete the dialog box as follows (a minimum area of 3 cm² is required for an object to be identified as a leaf):

  

• The leaves are now outlined.

  

• The characteristics of the 6 leaves are displayed in the measurements list, and the mean area and perimeter are displayed in the statistics window:

  

• Select Hide Binary layer in the Binary menu so you can judge how well the areas fit the leaves.