The Scale dialog allows you to view and set the mapping of data values into image intensities. Because it also displays a histogram of the data values, it is also often used to look at the distribution of data values.
At the center of the dialog is a blue region in which the histogram is displayed and which is overlayed with a line graph schematically showing how the data values are mapped to image intensities. You can change this mapping by editing the four values in the Scale field or by adjusting the line graph with the mouse. The range of data values covered by the histogram is set by the field just below the histogram display.
Overview | Wave selection | Options | Scaling values | Histogram | Using wave scale | Using the mouse | Graph range | Other controls
The toggle buttons at the top of the menu indicate the wave in view. Pushing one of the toggles will cause that wave to be displayed in the image window. The scale and histogram information will also be updated.
When the image window is displaying the data as a grayscale and the wave viewed is changed, the wave toggles in the Scale menu are updated to reflect the wave currently in view.
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The Options menu has settings which can be toggled on or off to control some less commonly used features. A feature is on when an x is displayed next to it in the menu.
When the 3D Histogram option is set, the histogram includes data from all z sections in the current wave and time. By default, this option is off and only the values from the current section are used for the histogram calculation.
When the Binary option is set a binary scaling (actually a linear scaling with a very small difference between the minimum and maximum) is forced and, in addition to altering the scaling values for the data set, Scale alters the recommended threshold value.
When the Autorange option is set and a new section is displayed, the bounds on the histogram display are automatically adjusted to accommodate both the scale for the section and the range of data values. This is the default behavior when scaling data in a scratch window.
When the Autoscale option is set and a new section is displayed, the scale is automatically adjusted to be a linear scale between the minimum and maximum data values in the new section. By default, this option is off. When it is turned on, the Using wave scale toggle will be toggled off; if that toggle is toggled on, autoscaling will be turned off.
When the Filter option is set and a new section is displayed, a scale is automatically chosen by shifting the current scales based on where the peak in the histogram is. By default, this option is off.
Because the 3D Histogram and Filter options rely on the histogram calculation, they automatically turn on the histogram display when selected and are turned off if the histogram display is turned off.
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The mapping the from data values to intensities is set by four values that are shown in the Scale field. A data value, x, between the first value, v0, and the second value, v1, is mapped to an image intensity, I, using this formula when v1 is greater than or equal to v0
I = IMax * (( x - v0 ) / ( v1 - v0 ))^Gamma
where Gamma is the third value in the field. Data values greater than v1 are either displayed as the maximum intensity if the fourth value in the field is not one or as the minimum intensity if the fourth value is one. When v0 is greater than v1, the mapping is
I = IMax * ( 1 - (( x - v0 ) / ( v1 - v0 ))^Gamma )
and values greater than v0 are mapped to the minimum intensity if the fourth value in the field is not one or as the maximum intensity if the fourth value in the field is one.
In the special case where the first and second values both zero, the image window has an autoscaling mechanism in which each section is linearly scaled based on the minimum and maximum of a sample of points from the section.
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This toggle button turns off the calculation and display of the histogram and is useful when the overhead for those calculations isn't desired. The line graph representing the mapping is still shown. Some options will, as a side effect, turn on the histogram display; these same options are turned if they are in use when the histogram display is turned off.
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For each section, the scale that is applied is either a scale associated with just that section, if such a scale has been set, or the scale associated with the wave. When viewing and changing the scales with Scale, how you use these two different sources for the scaling parameters is restricted to keep things simpler. When the Using wave scale toggle is on, all sections in a wave use the scale associated with the wave, and the scale parameters shown are those of the wave's scale. When it is off, all sections use their own scales (for any of these that haven't been set they are initialized with the scale associated with the wave), and the scale parameters shown are those for the current section's scale.
Besides manually toggling the Using wave scale toggle, there are situations when it is automatically changed. When a new wave is selected, the toggle is toggled on if the newly displayed section doesn't have its own scale set and it is toggled off if the new section does have its own scale. Also, if the autorange option is enabled, it is toggled off. If at some point, the toggle is manually toggled on, the autorange option is turned off if it was on. Finally, if the Load button is pressed, the toggle is toggled on because the only scales affected by that button are those associated with each wave.
Overview | Wave selection | Options | Scaling values | Histogram | Using wave scale | Using the mouse | Graph range | Other controls
You can use the mouse to adjust the image scale by altering the line graph displayed in the dialog. There are three control points on the line graph. If you place the pointer on one of the outer points, depress the right mouse button, and keep it depressed while moving the mouse, you will shift the upper or lower bound for the scale. The same operation with the central point can be used to simultaneously shift both the maximum and minimum, i.e. slide the scale. If you place the pointer on either of the segments between the boxes and drag the pointer with the right mouse button held down, you will alter the shape of the curve. When the binary option is on, the only movement that is possible is sliding the scale.
When adjusting the curve with the mouse, the outer control points can't be pushed beyond the bounds of the histogram display. Adjust the values in the Graph Min/Max field to alter these bounds. When the outer control points have little horizontal separation, you'll no longer be able to reshape the curve, but pointing at the segment between the outer control points, depressing the right mouse button, and moving the pointer will slide the scale.
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The minimum and maximum data values represented in the histogram display are shown in the Graph Min/Max field. You can change these values. This can be useful when adjusting the scale with the mouse or with the Brightness or Contrast buttons.
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The Brightness button will shift the scale by a factor (5%) of the difference between the upper and lower bound of the scaling. Clicking on the right side of the button shifts the scale downward causing the image to appear brighter, clicking on the left side of the button has the opposite effect.
Clicking the right side of the Contrast button reduces the difference between the upper and lower bounds for the scale enhancing the contrast in the image. To lower the contrast (expand the range of the scale), click on the left side of the Contrast button.
Neither of these buttons will cause the scale to fall outside of the bounds on the histogram display, so you may want to change these bounds before using the Contrast or Brightness buttons.
The Save button records the current scales and the name of the file viewed in a database. ViewFile and CopyRegion have options to read the saved scales for a file when the file is loaded into a window. The Load button can be used to load the saved scales after the file is opened. If the Using wave scale is off, be aware that the only scales recorded are the those for each wave; the scales for each section are not stored.
The Reverse button will change the scaling to give the negative image.
The Reset button is intended to provide a limited undo capability. It will restore the scale in use at the most recent occurrence of any of the following events:
The Load Default button loads a linear scale whose range is based on minima and maxima recorded when the image window was created (the extreme values for the wave are used when the Using wave scale toggle is on; otherwise the extreme values for the current section are used). The minima and maxima are not recalculated. If they were not set or were set to unintelligible values when the window was created, the scale won't change and an error message will be displayed; otherwise, the new scale range is just what the application that created the window set the range to be, and it may not be the same as the actual range of data values.
Overview | Wave selection | Options | Scaling values | Histogram | Using wave scale | Using the mouse | Graph range | Other controls