Zoom and Display
Once you have loaded some images, you can display them in the "image viewer" box by clicking the name of the image in the "Frame list" section.
To shift the image in the image viewer control, use the scrollbars or simply drag the image while pressing the left mouse button (pan-and-scan function). Use the zoom control to modify the zoom of the image.
Three types of zoom are availabe:
zoom: no
zoom: fit
zoom: full
If the images are in grayscale format, then they can be displayed in false colors using a colormap (see Preferences).
Here there is and example of grayscale image...
... and the same image displayed using the 'JET' colormap
Sometimes an image is too dark to see its details (for example when you want to remain in the linear zone od the sensor). To override this problem yaou can use the contrast bar.
Three types of contrast are available: none, full, yes.
First of all, to explain how these three types of costrast work, we define the image I as a matrix of pixels of dimensions WxHxC where W and H are the width and height of the image and C is the number of color components. For example a gray scale image have one color component (C=1) and an RGB image have three colo components (C=3). If we define (x,y,c) the pixel at position (x,y,c) and IMAX=max{I(x,y,c) for each x,y,c} and IMIN=min{I(x,y,c) for each x,y,c} the absolute maximum and minimum computed on the whole image then the following type of contrast can be defined:
- None: the contrast of the image is computed automatically to have the balck level set to min{0;IMIN} and the withe level set to 255 if IMAX≤255 or 65535 if 255<IMAX≤65535 or IMAX if IMAX>65535
- Full: the black level is set to IMIN and the white level to IMAX.
- Yes: all pixels for which I(x,y,c) ≤ PMIN×IMIN are black and all pixels for which I(x,y,c) ≥ PMAX×IMAX, are white where PMIN e PMAX are percentual choose by the user.
Here there is a portion of an image of the variable star DY-Pegasi...
... and the same picture but with the contrast modified to make the stars visible.