i cry

## December 7, 2019
## HW9 - Working with data files(again)

## Objectives:
    ## working with lists.
    ## continued practice:
        ## reading from and writing to files.
        ## designing with control structures and functions.

## This program will:
    ## read in data from the user's file input.
    ## create 2 new image files with the following characteristics:
        ## an image with all of the blue values 'negated.'
        ## a gray scale version of the image as well.

## Welcome Greeting:
print('Image Color Converter')
print('This program will open and read in data from the image file of choice.')
print('It will also create 2 new image files-'
      '\n' '\t' 'First: Image that will negate all blue values.'
      '\n' '\t' 'Second: Grayscale version of the image.')

## [ I N P U T ]
## main()function will include:
    ## user prompt for file input.
    ## error messages.
    ## creating the new file with results.
def main():

    tryAgain = True ## exit sentinel regarding about continuation

    while tryAgain == True:

        while True:
            try:
            ## prompting user file input.
                inputFile = input(str('Enter image file name to convert \
                (include \'.ppm\'): '))
                selectFile = open(inputFile, 'r') ## opening and read file.
                dataFile = selectFile.read()## storing inputFile data.


                rawArray = [] ## creating empty list to store dataFile elements

                ## placing each color value into its designated index

                rawArray = dataFile.split()

                maxColorValue = int(rawArray[3])

                ## creating empty list to store group of elements
                pixelArray = []

                for idx in range(4, len(rawArray) - 4):

                    try:
                        pixelArray.append(int(rawArray[idx]))
                    except ValueError:
                        pass

                blueImage = negateBlue(pixelArray, maxColorValue)

                ## calling outputFile() to create file.
                outputFile(blueImage, inputFile, rawArray, '_negate_blue.ppm')


                greyImage = greyScale(pixelArray, maxColorValue)
                outputFile(greyImage, inputFile, rawArray, '_greyscale.ppm')


                selectFile.close() ## closing current input file.
            ## ERROR MESSAGE: displays when the user enters incorrect file name
            ## or file path.
            except FileNotFoundError:
                print('Wrong file or file path. Please enter correct file!')
                print()
                print()
            else:
                break ## breaking out of the loop.

        yesno = True ## exit sentinel for wrong input.
        ## If user enter any value that is not a YES or NO, this will display
        ## the decision prompt again until they enter any of the correct value.
        while yesno == True:
            decision = input('Do you want to convert another file? Yes or No?')
            print()
            print()

            if decision.lower() == 'no':
                print('----- End of Program -----')
                print()
                print()
                ## Flag Variable - this will close the loop and end the program.
                tryagain = False
                ## Loop exits.
                yesno = False

            ## Displays message if the user does want to continue.
            ## This will also loop back to main().
            elif decision.lower() == 'yes':
                print()
                print()
                yesno = True

            ## Error message if user enters anything besides the YES/NO options.
            else:
                print('ERROR: Please enter YES or NO.')
                print()
                print()
        tryAgain = False


## outputFile() function will:
    ## create two NEW output file.
def outputFile(pixelArray, inputFile, rawArray, extName):
    ## removes the .ppm or '.' extension in the original inputFile name.
    removedExtension = inputFile.replace('.ppm', '')

    ## opens and writes new file to log results.
    ## first outFile - negating blue
    outFile = open(str(removedExtension) + extName, 'w+')


    outFile.write(rawArray[0] + ' ')
    outFile.write(rawArray[1] + ' ')
    outFile.write(rawArray[2] + ' ')
    outFile.write(rawArray[3] + ' ')

    for idx in pixelArray:
        outFile.write(str(pixelArray[idx]) + ' ')


## changing pixels to opposite of blue value
def negateBlue(pixelArray, maxColorValue):
    for idx in pixelArray:
        if idx % 3 == 2:
            pixelArray[idx] = 255 - pixelArray[idx]
    return pixelArray

## calculates rgb pixels and changes it to gray
def greyScale(pixelArray, maxColorValue):

    index = 0 ## count

    while index + 3 < len(pixelArray):

        x = int((pixelArray[index] + pixelArray[index + 1] \
             + pixelArray[index + 2])/ 3)

        pixelArray[index] = x
        pixelArray[index + 1] = x
        pixelArray[index + 2] = x

        index += 3

    return pixelArray

main()