BioImage allows editing of a transfer function. A transfer function assigns color (and other properties) to three dimensional data to help the user comprehend the data visually. Figure 2.16 shows BioImage's interface for editing transfer functions.
To edit the transfer function, press , located in the Visualization Settings pane's Volume Rendering Tab, see Figure 2.11 item 3. The new paint layer appears in the list of current editing widgets. To remove any layer, click the red X delete button next to the paint layer to remove it from the available widgets. You may also turn it on or off using the On toggle. After removing the paint layer, the transfer function editor should look as it does in Figure 2.16.
The transfer function editor displays a histogram of data values as shown in Figure 2.17.
The histogram's horizontal axis corresponds to the dataset's range of values. For the tooth dataset the measure quantity is density. For the tooth dataset, density values range from 0-1300.
The histogram's vertical axis measures gradient magnitude. Areas of high gradient magnitude correspond to material borders in the dataset. Areas of low gradient magnitude correspond to different materials in the dataset.
Other transfer function editor controls are used to toggle a transfer function on/off, change its color, or assign it a name. Transfer function sets can be saved to disk and later reloaded.