The Display Settings

Gray Value

The number under these words is the value stored in the screen buffer for the pixel under the cursor. This is not the same as either the real part or imaginary part of the big array. However if you are displaying the real part you will see that a value of zero in the real part corresponds to 127 in the grey value. These numbers correspond to the grey value displayed upon the screen. If colorized 127 corresponds to black negative values to magenta and positive values to yellow. If you really want to get confused "enter gray" and try to interpret the results. It makes sense but cant be said. You should try setting the "literal values" box on the histogram tray, and experimenting with it. I wrote it and still get confused. All variations that I have experimented with are also confusing in some situation or other.

Display Modes

The "real part" in the display above is a pull down menu which when selected shows the following.

These choices permit you to select what aspect of the "Big Complex Array" you will have displayed upon the screen. If you select "Magnitude" or "Mag Squared" the display will show the largest value as black (255 gray) and zero as white. The other choices display zero medium gray (127) and the extreme value as either black or white. The "Phase Angle" displays -180° as white and +180° as black. Notice that the display is always re normalized so as to show as much information as possible.

If the "black & white" check box is selected the display is literally that. For "real part", "imaginary part", and "Phase Angle" the display makes all values greater than zero black and the rest zero. For "Magnitude" and "Mag Squared" all values more than half way between zero and max. are black.

At the left side of the box the display value of the point under the cursor is displayed. You can compare this value with the values shown bellow the coordinates to gain a greater understanding of how the values stored in the big array are translated onto the screen.

About the Magnification Stepper

The number displayed next to the stepper represents the magnification of the pixels being displayed. "1" means that each point in the array is represented by one pixel in the display. "2" means that each point is represented by a 2x2 square etc. There are 4 magnifications 1,2,4, and 8.

Since the the displayed screen is 512 by 512 pixels the 128 array is only displayable at magnification 4 and 8. The 1024 array is displayed a peace at a time. At large magnification it is easy to get lost in the larger screen sizes. Some useful tricks are explained with the section on drawing tools. To display the whole 1024 array it is necessary to use the "Big Window" menu option.

LV Comp [Light Valve Compensation]

The purpose of this option is to permit you to map the gray scale of the screen to compensate for characteristics of the display device. The mapping is done with a table which must be loaded before the option is used. The window above will appear when the "Filter" button is clicked the first time. After the filter table has been loaded another click of the "Filter" button will cause all of the gray levels of the screen to be changed. Only the screen buffer will be changed. The big array is not read or used un the application of this table. The use of this function can be highly confusing so some caution should be used. When something has been displayed on the screen the screen, the screen contains an integer in the range of 0 to 255 corresponding to the degree of grayness of the display, when the real part, imaginary part, or phase is displayed the value of 127 (a very middle gray) corresponds to the value zero, negative values are lighter and positive values are darker. If you were to click "enter gray" the pixels with value 127 will be entered into the real part with a value of zero, the pixels with 0 will be entered into the real part with value -127 and so forth. This was not intended as a way to change the big array but only for re calibration of the gray display. It can be used for manipulation of the contents of the big array however.

The filter requires 256 numbers in a column of simple text saved or pasted into the filter window. If a particular pixel has a value of say 102 when the filter button is clicked the 102'nd entry in the table is looked up and the value found there is applied to that pixel on the screen. As soon as a table is loaded the function is displayed as a graph. and when the apply filter is clicked the function is used. If you click the "Filter" button again, instead of displaying the dialog, the filter is immediately applied. If you wish to change the function after loading a filter, select the "Load Filter Function" item on the file menu.

This effects the display in the big window as well. (which is the whole point)

You will see that the histogram changes. This is to help you see the action of the filter and should not make you think that the contents of the big array have been changed. They have not been changed.

The filter is not permanent if a calculation or entry is made the screen changes and the filter must be reapplied. If the filter is clicked twice things get really weird.

WHEN USED IN A SCRIPT - It will cause the re-display of the screen with the filter applied. The filter will be applied to the current screen every time it is executed by the script. So you should make sure that the screen displays what you want to filter before execution gets to this icon. Each occurance of the "Filter Icon" can have a different filter. Read more about using this in a script.

The Color Spot

You notice that nearly all of the windows have a color square. This is to help keep track of which dialog window operates on which document window. You can have five sets of windows. Notice that the "Window" menu shows all of the windows that you have opened in the program and the color associated with the window.