PlayBASIC Code - AFX Alpha Channel Blending - Cross Fading Dogs AVA and GODA

[kevin]

  PlayBASIC Source Code - AFX Alpha Channel Blending - Cross Fading Dogs AVA and GODA


    This demo creates a waving alpha channel on the foreground image which is then rendered over the background image.  Since the foreground is an AFX image it'll be alpha blended over the background.. Looks a lot more interesting than just a fixed variable alpha blend.   

     To do this in PlayBASIC V1.65 we have to create a strip image for the Alpha channel blending levels.  This is then added to the foreground image.  This is a bit tricky as DrawIMAGE doesn't seem to support Alpha Addition; so we have to resort to using sprites here.   Which do have Alpha addition rendering modes.   Which works none the less.

    NOTE: For this demo; you'll need to supply two Images that are same size..   

PlayBASIC Code: [Select]

openscreen 1200,800,32,1

positionscreen GetScreenXpos(),GetScreenYpos()*0.2


      IMage =LoadNewaFxImage("Image1 - 1200by900.png")    //  INSERT THE FILE NAMES HERE
      
      IMage2=LoadNewaFxImage("Image2 - 1200by900.png")




      // CReate a strip we'll render alpha channel levels to
      Strip=newfximage(GetImageWidth(Image),2)
      
      // CReate sprite using out strip image, so we can render it
      // using Alpha Addition
      Sprite=Newsprite(0,0,Strip)
      spritedrawmode Sprite, 2+   16   
      
      
      
      //  CReate an FX size image for our screen
      Screen=NewImage(GetScreenWidth(),getScreenHeight(),true)      
      
      Do
      
      
         //  Compute the a strip of alpha blend levels
         //  These are just 
      
      
         rendertoimage Strip
         w=getimagewidth(Image)   
         AStep#=255.0/W
         for xlp=0 to w-1
               Alpha=ClipRange(128+sin(Xlp*Astep#+Angle)*128,0,255)
               Colour=Argb(Alpha,00,00,00)
               dotc xlp,0,Colour
         next
         Angle++


         //  Mask off the Alpha channel from the foreground image
         rendertoimage image
         inkmode 1+256
         boxc 0,0,GetSurfaceWidth(),GetSurfaceHeight(),true, Argb(0,255,255,255)


         //  Render the strip image (of alpha channel) over the foreground
         //  this is ADDED to the foreground image setting the alpha
         // channel levesl for each picture in the image
         For ylp=0 to GetSurfaceheight()-1
            Positionsprite Sprite,0,ylp
            drawsprite sprite
         next   
         inkmode 1



         //  Render the background and foreground image to our
         // FX screen image         
         rendertoimage Screen
         drawimage  Image2,0,0,false   ; Draw backdrop SOLID
         drawimage  Image,0,-50,true   ; Draw foreground Transparent Alpha BLENDED 

         //  Render to screen to the PlayBASIC Screen
         rendertoscreen
         drawimage screen,0,0,false

         
         sync
      loop spacekey()=true

   

[ Credits ]
    Music: Synapse by Shane Ivers - https://www.silvermansound.com