The WDEFROI function allows the user to select and cut-out an arbitrary shaped region-of-interest (ROI) from a displayed image via point and click with the mouse. With WDEFROI one can isolate a small intricately shaped active region from a larger image for further analysis. This can be particularly useful for reducing the computation time for calculating temperatures and emission measures of large data cubes. WDEFROI is not SXT specific, so it can be used on ground-based data or other derived data such as temperatures and emission measure. One can obtain light curves of the selected ROIs by passing normalized data and the times of data.
Example call to WDEFROI to obtain a sub-image via the keyword image:
IDL> sub_img = wdefroi(data, /image)
The program starts by bringing up the 1st image and running STEPPER
to allow the user to pick a working image frame from the variable data for
selecting ROIs (One can specify the working image frame by using the
sub=image_number keyword and avoid running STEPPER). Once the working frame
has been selected (say image 5), the user should exit STEPPER, and a widget
window will appear entitled WDEFROI.
The top row of buttons of this widget is used to pick the mode of ROI selection and to change the color table (via XLOADCT). Below these buttons is the online instruction box which displays useful general information and specific information on how to make box, polygon, and contour selections with the mouse. This is followed by some contour controls, namely a slider widget which can be used to set the contour level at a specific value. Then there is a row of control buttons: a select button to blacken-out all but the selected area of the image; reset button to re-display the original image; light curve to display a light curve of the selected area; exit to quit the widget and to return to IDL command line. The final row has a display box for the total number of pixels selected by box, polygon, and contour.
Example call to also plot light curves from normalized data:
IDL> sub_img = wdefroi(norm_data, /image, zoom=6, sub=5, /lc, time=index)
Where, norm_data is a data cube of small images say 64 by 64 pixels, zoom
specifies a zoom factor of 6, lc keyword requests light curve plot, and the
times for the light curve are passed via the time keyword.
Note: If the input data cube contains full frame images and the area of interest is very small it may be best to call WDEFROI twice: 1st to isolate the general area from the full context image and a second time with some zoom factor to make contouring and extracting the smaller features easier.