How do I control the grayscale in an image window?
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Q8. How do I control the grayscale in an image window?
Normally, each slice is displayed with its intensity-to-grayscale (I->G) map chosen to make that particular image look decent. Displaying a new slice will result in a new I->G map being used. (This is also true in a Montage--each slice shown will have its own I->G map.) There is an undocumented way to make the I->G map fixed for a given image viewing window. Its usage is a little clumsy:
- Right click in the intensity scale bar just to the right of the image window. This will popup a hidden menu.
- Pick the item "Choose Display Range".
- This gives a control window with the instructions
Display range: bot top [ztop]
In this window, type the intensity value you want mapped to the darkest level (bot), a space, and the intensity value you want mapped to the brightest level (top). You might choose these values from the scales shown just below the image slider, but you will probably need to experiment. Then press the "Apply" button. - From this point, the slices displayed in this window will bypass the normal scaling and be mapped linearly from bot->darkest to top->brightest. Values below bot also map to darkest, values above top also map to brightest. If you type a " 1" after the value of top, this is a flag to display values above top as dark instead of bright. In this way you can try to display only gray matter, say.
- To restore normal processing of the I->G map, you must enter bot and top both as zero, then press "Apply" (or "Set"). Note that if you close the image window (with the "Done" button), then reopen it, you get a new set of interface widgets that do not remember the settings you made previously.
This FAQ applies to: Any version.
