ITV enables you to interactively examine an image displayed on the video display. The mouse buttons and several keyboard keys are activated to perform functions when pressed:
|LEFT||ZOOM IN, centered on the cursor|
|MIDDLE||ZOOM OUT, centered on the cursor|
|RIGHT||PAN, move the pixel under the cursor to the center|
|E||EXIT ITV and return to VISTA (or resume procedure)|
|R||RESTORE image to the original zoom/pan|
|+||BLINK Forwards through the last 4 images.|
|-||BLINK Backwards through the last 4 images.|
|P||Find the PEAK pixel near the cursor & jump the cursor there|
|V||Find the LOWEST pixel ("Valley") near the cursor &|
|jump the cursor there|
|#||"Power Zoom" zoom at the cursor to the maximum zoom factor|
|H||Toggle between small and full-screen cross-hairs|
|F||FREEZE/UNFREEZE the Zoom window.|
|0-9||Mark the pixel coordinates and store in VISTA|
|variables Rn and Cn, where "n" is the number key hit|
|D||Print selected pixel row, column, and value.|
|Load variables R and C with the location.|
|]||Clear boxes and stuff off the image display|
The D key also loads the coordinates of the most recently selected pixel into VISTA variables R and C; the 0-9 keys load Rn and Cn, where n is the key struck. If the image had to be compressed to fit in the display window (auto or manual dezoom), the main display will not show every pixel, although the magnifying glass window will, so choose the pixel in that window.
You also have control of the color map (upper & lower contrast drag and color-map roll), see the X11 help page for details.
The ITV command is very useful in procedures for letting you use the D or 0-9 keys to extract position information from the image of interest needed elsewhere within the procedure. Recall that variables (or any arithmetic expression) may be used in place of a number in words of the form word=value. Here is an example of a procedure which draws a contour map of a section of an image located by the cursor. It draws at most a 51x51 box, but will draw a smaller section of an image if the cursor is placed near the edge of the frame.
ASK 'DISPLAY WHICH IMAGE >> ' BUF ! Get number of image MN $BUF; TV $BUF ! Display the image SROW=SR[BUF] SCOL=SC[BUF] ! Note start row/col EROW=SR[BUF]+NR[BUF]-1 ! Note end row ECOL=SC[BUF]+NC[BUF]-1 ! Note end column PRINTF 'PLACE CURSOR ON CENTER OF THE REGION TO MAP' PRINTF 'THEN HIT THE D KEY, FOLLOWED BY E' ITV ! Define center R and C NRSHOW=51 NCSHOW=51 DEL=IFIX[NRSHOW/2] ! Default size LOROW=R-DEL HIROW=R+DEL ! Limits to box LOCOL=C+DEL HICOL=C+DEL IF LOROW<SROW ! Edge adjustment LOROW=SROW END_IF IF HIROW>EROW HIROW=EROW END_IF IF LOCOL<SCOL LOCOL=SCOL END_IF IF HICOL>ECOL HICOL=ECOL END_IF NRBOX=HIROW-LOROW+1 NCBOX=HICOL-LOCOL+1 ! Size of box BOX 1 SR=LOROW SC=LOCOL NR=NRBOX NC=NCBOX CONTOUR $BUF BOX=1 END