Enhancements make the onscreen image clearer and easier to interpret without changing the values in the image file.
The available enhancements are as described in the following table.
| Button | Name | Description |
|---|---|---|
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None | Does not apply an enhancement to 8U data types. None does, however, apply a linear stretch or a linear enhancement to other data types by using their pixel values. The stretch is applied using only those pixels displayed in the viewer.
At a zoomed-out level, the pixel values are decimated before they are displayed in the viewer. Therefore, the range of pixels used for the linear stretch may be narrower than the actual range of pixels in the image file. This means that the actual minimum and maximum values in the image file may not be included in the calculation of the linear stretch. Tail Trim and Exclude Min/Max are ignored for all data types. |
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Linear | Uniformly stretch the minimum and maximum values in the image over the entire available output-display range to enhance the overall differences in gray levels in the image. |
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Root | Compress the range of higher values (brightness) and expand the range of lower values (darkness), so you can distinguish more detail in darker areas of an image while still retaining some detail in the brighter areas. |
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Adaptive | Combine the benefits of Equalization and Linear for a more natural display than Equalization while compensating effectively for outliers. |
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Equalize | Equally distribute the values over the entire output-display range resulting in an almost uniform histogram. Equalize is effective in exposing details in the higher values (brightness) and lower values (darkness), but causes less contrast in the middle values. |
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Infrequency | Assign the values that occur least frequently in the image to the range of higher values (brightness) in the histogram, so finer details become brighter. |
| Tail Trim | Remove the upper and lower two percent of the image histogram to eliminate outliers in the upper and lower part of the pixel range. Tail Trim uses a two-percent margin by default; however, you can adjust the amount of tail trim ranging from 0.1 percent through five percent by clicking Set Trim %. | |
| Exclude Min/Max | Disregard the lowest and the highest value in the image histogram before applying the tail trim. | |
| Set Trim % | Select a percentage (ranging from 0.1 percent through five percent) to remove from both the high and low end of the histogram before computing an enhancement. By default, two percent is removed.
For information about setting up a custom histogram trim, see Setting up custom histogram-tail trim. |