Blitter Objects

As with HREV, there is an equivalent hexadecimal version of the VREV function, which can be used with AMAL animation strings. The format is:

$4000+n

Where $4000 acts as the reversal flag, and n is the image number. Here are two typical AMAL string of reversed animation:

X> "Anim 0,($4000+1,2)($4000+2,2)($4000+3,2)($4000+4,2)"

X> "Anim 0,($4001,2)($4002,2)($4003,2)($4004,2)"

REV
function: double-flip an image vertically and horizontally
new number=Rev(image number)

REV combines HREV and VREV into a single function. It takes the image whose number is held in brackets, reverses it from left to right and then performs another reversal from top to bottom. For example:

E> Load "AMOSPro Tutorial:Objects/Bobs.abk"
   Curs Off : Cls 0
   Flash Off : Get Bob Palette
   Double Buffer
   For Y=200 To -40 Step -1
    Bob 1,Y*2,Y,1
    Wait Vbl
   Next Y
  For Y=-40 To 200
   Bob 1,Y*2,Y,Rev(1)
   Wait Vbl
  Next Y

Don't forget to try the HELP programs for a demonstration. If your own attempts at flipping Bob images cause any problems, you may wish to consult the Bob Doctor, below.

The Bob Doctor
Here are some free consultations which answer common problems encountered when flipping Bobs.

Problem: When I use flipped Bobs on screen with their original images, my display slows down to a crawl.
Remedy: Do not display the same image in different orientations on screen at the same time. AMOS Professional flips images during the updating process, just before Bobs are re-drawn on screen. Once reversed, images stay in this new state until displayed in a different direction. Whenever AMOS Professional flips a reversed image, it first needs to restore the image to its original state. This takes a great deal of processor time, and slows down your display.