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Regulate the intensity of the image

Button Function
Regulation of the intensity levels.

By clicking on the icon, the histogram of image levels appears on the bottom of the image. A first choice is made by selecting an interval containing 99.5% of the values.

It is possible to make other automatic choices by selecting them in the menu (the histogram will appear to show the choices).

It is possible to select a different stretch by clicking and dragging the mouse over the intensity interval one wants to display. The histogram disappear by clicking the same intensity icon. As you can read on the tutorial on contours, the levels used to draw contours on the image are shown as vertical bars on the intensity histogram.

To move the center of the colormap or change the contrast, one can move the mouse on the image by pressing its right button. Horizontal movements change the reference point of the color map (bias), while vertical movements change the contrast.

Button Function
Change the color map.

This icon opens a dialog window to change the color map, the stretch, and the color of the contours. The Reverse button inverses the color map. The choice of color maps include also popular DS9 choices. Avaible stretches include the linear stretch, the square root and square power, the natural logarithm and the power of 'e' (base of natural logarithm), the hyperbolic sinus and its inverse (hyperbolic arc-sinus). After doing the selection, press 'OK' to exit the dialog window.

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