The GUI Z SCALING Command

The Z-SCALING menu allows the range of intensity values displayed to be changed, and to control the manner in which data array intensity values are converted to output pixel colours.

Figure 11 is an example of the false colour display of 2-D data, together with the Z-SCALING menu for changing the manner in which pixel intensity values are displayed as different colours or grey levels.

Figure 11: Example of False Colour Image Data Display

The following commands are available:

EXIT: Exits Z SCALING sub-menu and return to calling menu.

+ MAXIMUM: Set fixed range scaling and increase maximum limit by 10% of the scaling range.

USER MIN/MAX: Prompt user for MINIMUM DISPLAY VALUE and for MAXIMUM DISPLAY VALUE, and set fixed range scaling to these values.

?: List of commands with short description of each command.

- MAXIMUM: Set fixed range scaling and decrease maximum limit by 10% of the scaling range.

USER MINIMUM: Prompt user for MINIMUM DISPLAY VALUE and set fixed minimum value for the displayed intensity range. The maximum is automatically defined by the ROI data values, and re-defined each time the ROI is changed or new data are displayed.

FULLY AUTOMATIC: Full range automatic scaling is set. The ROI is searched for the minimum and maximum values, and the scaling range is set. Each time the ROI is changed or new data are displayed the scaling range is re-calculated.

+ MINIMUM: Set fixed range scaling and increase minimum limit by 10% of the scaling range.

USER MINIMUM: Prompt user for MAXIMUM DISPLAY VALUE and set fixed maximum value for the displayed intensity range. The minimum is automatically defined by the ROI data values, and re-defined each time the ROI is changed or new data are displayed.

WEAK PEAKS This selects reduced range automatic scaling. This is designed to display the weak features of diffraction data. Often full range scaling is not very informative since the intensity range is dominated by a very few strong reflections, and little detail is seen in the majority of the image. In this mode, the average value and standard deviation of intensity values are calculated in several regions of the image. The minimum of the display intensity range is then calculated from the minimum of the mean minus three times the standard deviation, and the maximum is set to the maximum of the mean plus five times the standard deviation from each of the regions. Each time the ROI is changed or new data displayed the range is re-calculated.

- MINIMUM: Set fixed range scaling and decrease minimum limit by 10% of the scaling range.

LOG SCALE: Display the data on a logarithmic scale. (The LOG SCALE button is replaced with the LINEAR SCALE button.)

LINEAR SCALE: Display the data on a linear scale. (The LINEAR SCALE button is replaced with the LOG SCALE button.)

As well as linear scaling, logarithmic scaling is available through the LOG SCALE button. When logarithmic scaling is enabled this button is replaced by the LINEAR SCALE button. If zero or negative range limits are encountered when automatic range logarithmic scaling is being used, a small positive value will be used instead.

The Z SCALING menu may also be obtained by clicking within the intensity scale colour bar when in the main menus of the different interfaces. A ``rubber-band'' line appears from where the user clicked. Any of the menu commands can be clicked, or the intensity scale colour bar may be clicked a second time. If clicked a second time the two values within the scale are used to set fixed range scaling. If the user clicks outside both the menu and the intensity scale colour bar, then fully automatic scaling will be set. This allows quick and reasonably precise re-scaling from any interface.