### Contours

> DS9 can create and display contours as an overlay on an image. The Display Contours menu is used to display contours. To create, copy, paste, and configure contours, use the Contour Parameters menu.

> Contour Parameters

> When creating a new contour, a dialog box appears, in which the user selects the number of contour levels, smoothness, and the distribution of the contours.

> Contour Levels

> Specifies the number of contour levels to be generated. A typical number is between 1 and 10. Note: large numbers of contours can take a long time to generate.

> Contour Smoothness

> Specifies how smooth the contours are. A smoothness level of 1 will evaluate the contour at each image pixel. A level of 2 will evaluate the contour at every other pixel. The larger the number, the quicker the contour will be generated, and the less detail will be available.

> Contour Scale

> Specifies the distribution of the contour levels. A linear distribution will have equal spacing between contours, Log and Ln will be weighted at one end. There are two ways to indicate the contour scale, Use Frame Scale (automatic) and manual

> > Use Frame Scale

> > Use the color scale that the image is currently being displayed in. Therefor there is a one-to-one match between the image color scale distribution and the contour levels.

> > Manual

> > Manually indicate upper and lower levels and a distribution for the contour levels. The contours generated will not be matched to the image color scale distribution.

> Contour Method

> There are two methods that are available to calculate the contour lines. The first, BLOCK, blocks down the image, by the smoothness factor, before contours are calculated. As a result, the larger the smoothness, the faster the result. The second method, SMOOTH, smooths the image before calculating contours. As a result, the larger the smoothness, the slower the result.