#----------------------------------------------------------------------
# Fleshed-out command processor for image processing.
#
# (C) Copyright March 19, 2018 -- Dr. William T. Verts
#
# Old functions have been removed.
#----------------------------------------------------------------------

import string

#----------------------------------------------------------------------
# Here most of the functions do something to a pixel, but that is it.
# The double-loop, getPixel, and repaint have been factored out into
# the Process function, which in order to work must be passed as a
# parameter (FN) the actual pixel function to be applied.
#----------------------------------------------------------------------

def Brighten_Pixel(PX):
    setRed  (PX, getRed  (PX)+20)
    setGreen(PX, getGreen(PX)+20)
    setBlue (PX, getBlue (PX)+20)
    return

def Darken_Pixel(PX):
    setRed  (PX, getRed  (PX)-20)
    setGreen(PX, getGreen(PX)-20)
    setBlue (PX, getBlue (PX)-20)
    return

def Monochrome_Pixel(PX):
    Average = (getRed(PX) + getGreen(PX) + getBlue(PX)) / 3
    if Average > 128:
        setColor(PX,white)
    else:
        setColor(PX,black)
    return

def Negate_Pixel(PX):
    setRed  (PX, 255 - getRed(PX))
    setGreen(PX, 255 - getGreen(PX))
    setBlue (PX, 255 - getBlue(PX))
    return
    
def Gray_Pixel(PX):
    Average = (getRed(PX) + getGreen(PX) + getBlue(PX)) / 3
    setRed  (PX,Average)
    setGreen(PX,Average)
    setBlue (PX,Average)
    return
    
def Process (Canvas, FN):
    for Y in range(getHeight(Canvas)):
        for X in range(getWidth(Canvas)):
            FN(getPixel(Canvas,X,Y))
        repaint(Canvas)
    return

#----------------------------------------------------------------------
# Functions that have to be stand-alone, and cannot be used with
# Process.  Flip and Mirror have to deal with pairs of pixels at
# a time.
#
# Question: In Mirror, what happens to the middle pixel of each row
# when the canvas is an odd number of pixels wide?
# Is it ignored, or is it swapped with itself?
#
# Question: Can we factor out the code to swap pixels?  It'll be the
# same in both Flip and Mirror.
#----------------------------------------------------------------------

def Mirror (Canvas):
    for Y in range(getHeight(Canvas)):
        for X in range(getWidth(Canvas)/2):
            PX1 = getPixel(Canvas, X, Y)
            PX2 = getPixel(Canvas, getWidth(Canvas) - 1 - X, Y)
            Color1 = getColor(PX1)
            Color2 = getColor(PX2)
            setColor(PX1, Color2)
            setColor(PX2, Color1)

        repaint(Canvas)
    return

def Flip (Canvas):
    # Currently a stub.
    return
    
#----------------------------------------------------------------------
# The updated command processor.  Notice that GrayScale still uses
# the explicit function, and hasn't yet been updated to the new
# style using Process.  All the other image commands call Process,
# but must tell Process which pixel function to use as parameter FN.
#----------------------------------------------------------------------

def Main():
    Message = """Enter a Command
from the list:
QUIT OPEN
SAVE BRIGHTEN DARKEN MONO GRAY NEGATE
MIRROR FLIP
FOCUS EMBOSS CONTRAST
Enter a command --- """
    Canvas = makeEmptyPicture(100,100)

    MoreToDo = True
    while (MoreToDo):
        repaint(Canvas)
        S = string.upper(requestString(Message))
        print S
        if   (S == "QUIT"    ): MoreToDo = False
        elif (S == "OPEN"    ):
            Filename = pickAFile()
            Canvas = makePicture(Filename)
        elif (S == "SAVE"    ): pass        
        elif (S == "BRIGHTEN"): Process(Canvas, Brighten_Pixel)                
        elif (S == "DARKEN"  ): Process(Canvas, Darken_Pixel)
        elif (S == "MONO"    ): Process(Canvas, Monochrome_Pixel)
        elif (S == "NEGATE"  ): Process(Canvas, Negate_Pixel)
        elif (S == "GRAY"    ): Process(Canvas, Gray_Pixel)
        elif (S == "MIRROR"  ): Mirror(Canvas)
        elif (S == "FLIP"    ): Flip(Canvas)
        else: showError("ERROR, " + S + " is not a legal command")    
    return