def mirror(pic):
  pxl=getPixels(pic)
  w=getWidth(pic)
  h=getHeight (pic)
  for x in range (1,w):
    for y in range (1,h/2):
      clr=getColor(getPixel(pic,x,y))
      newPxl=getPixel(pic,x,h-y)
      setColor(newPxl,clr)


def chromakey(bg):
  bgH=getHeight(bg)
  bgW=getWidth(bg)
  greenPic=makePicture(pickAFile())
# xoff=requestInteger("X offset")
  # yoff=requestInteger("Y offset")
  for p in getPixels(greenPic):
     r =getRed( p )
     g =getGreen( p )
     b =getBlue( p )

     if (r + b > g): #if its NOT green
      x=getX(p)
      y=getY(p)
#    if (y+yoff<bgH)and(x+xoff<bgW):
      if (y<bgH)and(x<bgW): # Make sure the pixel exists in the Background pic
        nuColor=getColor(p)
  #    bgPixel=getPixel(bg,x+xoff,y+yoff)
        bgPixel=getPixel(bg,x,y )
        setColor(bgPixel,nuColor)


def invert(picture):
 pxl=getPixels(picture)
 for pixel in pxl:
   r=getRed(pixel)
   g=getGreen(pixel)
   b=getBlue(pixel) 
   r=255-r
   g=255-g
   b=255-b
   newColor=makeColor(r,g,b)
   setColor(pixel,newColor)


def grayscale(picture):
  pxl=getPixels(picture)
  for pixel in pxl:
   r=getRed(pixel)
   g=getGreen(pixel)
   b=getBlue(pixel) 
   grey=(r+g+b)/3
   newColor=makeColor(grey,grey,grey)
   setColor(pixel,newColor)



#Open a file
fred=pickAFile()
cledus=makePicture(fred)
show(cledus)

#Use a FLITER here
choice=requestInteger("Choose a Filter\0=Greyscale 1=Invert 2=Chromakey 3=mirror")
if (choice==0):
  grayscale(cledus)
if (choice==1):
  invert(cledus)
if (choice==2):
  chromakey(cledus)
if (choice==3):
  mirror(cledus)

#repaint the pic
repaint(cledus)

#How to save pic
pathway=requestString("Save picture as")
if(pathway!=''):
  folder=pickAFolder()
  pathway=folder + "\\" + pathway + ".jpg"
  printNow(pathway)
  writePictureTo(cledus,pathway)