The MATHS Sub-Menu

The MATHS sub-menu contains commands which allow mathematical operations to be applied to the pixels of the current region of interest. The MATHS sub-menu is shown in Figure 27.

Figure 27: The MATHS Sub-Menu Commands

The available commands and their functions are:

EXIT: Leave MATHS sub-menu, and return to IMAGE PROCESSING (GENERAL) main menu.

SCALAR /: Pixel by pixel division of the current region of interest by an input scalar value. The user is prompted DIVISION CONSTANT for the scalar which will be used for division.

HELP: Detailed help text on the interface and the available commands. The operation is performed in-place.

LOG(10): Take the logarithm (base-10) of all the pixel values in the current region of interest. If zero or negative values are encountered the user is prompted LOWER THRESHOLD, and the value entered will be used as the lowest value in the output. The operation is performed in-place. (Note: This changes the data values, unlike the log scaling option in the Z-SCALING menu, which only affects the display.)

SUBTRACT: Subtracts pixel by pixel, the image in the ``memory'' from the image in the current data array, within the current region of interest. The ``memory'' data must be defined throughout the current region of interest or a warning message will be produced. The operation is in-place.

?: Help text with short explanation of commands.

SCALAR *: Pixel by pixel multiplication of the current region of interest by an input scalar value. The user is prompted MULTIPLICATION CONSTANT for the scalar which will be used for the multiplication.

MULTIPLY: Multiples pixel by pixel, the image in the ``memory'' and the image in the current data array, within the current region of interest. The ``memory'' data must be defined throughout the current region of interest or a warning message will be produced. The operation is in-place. The original data is replaced by the result of the multiplication.

THRESHOLD: Allows minimum and maximum thresholding values to be set for the current region of interest. The user is prompted MINIMUM THRESHOLD VALUE and MAXIMUM THRESHOLD VALUE. Values outside of the set range are replaced will the minimum or the maximum value. The original data is replaced. Note: This operation is in general non-reversible.

HELP: Detailed help text on the interface and the available commands. The operation is performed in-place.

ADD: Add pixel by pixel, the image in the ``memory'' and the image in the current data array, within the current region of interest. The ``memory'' data must be defined throughout the current region of interest or a warning message will be produced. The operation is in-place. The original data is replaced by the result of the addition.

NORMALISE: Divide pixel by pixel by the largest value, throughout the current region of interest. The original data is replaced by the result of the division.

X(n): Calculate pixel by pixel $x^n$ where $x$ is a user specified constant, and $n$ is the value of each input pixel. The user is prompted ENTER POWER for the value of $x$. If $x$ is 10.0 this operation is the partial inverse of the LOG(10) operation. It is only a partial inverse in the case that values have been thresholded in the LOG(10) operation.

SCALAR +: Pixel by pixel addition of the current region of interest with an input scalar value. The user is prompted ADDITION CONSTANT for the scalar which will be used for the addition.

DIVIDE: Divides pixel by pixel, the image in the current data array by the image in the ``memory'', within the current region of interest. The ``memory'' data must be defined throughout the current region of interest or a warning message will be produced. The operation is in-place.

STATISTICS:

Allows the user to define an arbitrary polygon region with graphical coordinate input, and calculates a number of statistics in the region. If only two coordinates are input, they define opposite corners of a rectangular region for the calculation. The result is displayed in a text window, and can be saved to an output file.

A typical result of the STATISTICS operation is shown below.

Extremes of polygon (X/Y min, X/Y max) =
    704.85    993.16    761.94   1136.49
Number of pixels inside polygon =     3237
Smallest value =   1.0841     Largest value =   1.4180
Total intensity =   3688.0     (square root =   60.729    )
Average intensity =   1.1393
Root Mean Square (RMS) value =   1.1416
Standard Deviation =  7.15076E-02 Gain (?) =  4.48806E-03
Integrated intensity minus previous average =   61.607
Square root of above =   7.8490

The Integrated intensity minus previous average contains the integrated sum of pixel values minus the previous average value. Thus, if first a background region is defined, and then a peak is defined a simple form of peak integration is performed.