Compressing Similar PNG Images

imCompress.py

#!/usr/bin/python

from PIL import Image
import numpy
import argparse
import os
import sys


#Configure argument parser to take input arguments
parser = argparse.ArgumentParser(description='Compress similar PNG images')
parser.add_argument('firstFile', type=argparse.FileType('r'),
                   help='First Image File')
parser.add_argument('secondFile', type=argparse.FileType('r'),
                   help='Second Image File')
args = parser.parse_args()


#Open first image
firstImageObject = Image.open(args.firstFile.name)
firstImMode = firstImageObject.mode


#Convert first image to array
if (firstImMode == 'L'):
    print ('L')
    firstImage = numpy.asarray(firstImageObject)
    firstImageChannels = 1
elif (firstImMode == 'P'):
    print ('p')
    firstImage = numpy.asarray(firstImageObject.convert('RGBA'))
    firstImageChannels = 4
elif (firstImMode == 'RGB'):
    print ('rgb')
    firstImage = numpy.asarray(firstImageObject)
    firstImageChannels = 3
elif (firstImMode == 'RGBA'):
    print ('rgba')
    firstImage = numpy.asarray(firstImageObject)
    firstImageChannels = 4
else:
    sys.exit("This type of image can't be handled, maybe it is palette based")


#Open second image
secondImageObject = Image.open(args.secondFile.name)
secondImMode = secondImageObject.mode


#Convert second image to array
if (secondImMode == 'L'):
    secondImage = numpy.asarray(secondImageObject)
    secondImageChannels = 1
elif (secondImMode == 'P'):
    secondImage = numpy.asarray(secondImageObject.convert('RGBA'))
    secondImageChannels = 4
elif (secondImMode == 'RGB'):
    secondImage = numpy.asarray(secondImageObject)
    secondImageChannels = 3
elif (secondImMode == 'RGBA'):
    secondImage = numpy.asarray(secondImageObject)
    secondImageChannels = 4
else:
    sys.exit("This type of image can't be handled, maybe it is palette based")


#Check to make sure the images have the same number of channels
if (firstImageChannels != secondImageChannels):
    sys.exit("The two images have a different number of channels")


#Check to make sure the images are the same size
if (firstImage.shape != secondImage.shape) :
    sys.exit("Image dimensions don't match")


#calculate difference and sign images
differenceImage = numpy.subtract(firstImage.astype('int'), secondImage.astype('int'))
absoluteDifferenceImage = numpy.abs(differenceImage)
imageSign = 255*(differenceImage < 0).astype('uint8')


#Write sign and difference images to file for each channel
for channel in range(0,firstImageChannels):
    if (firstImageChannels == 1):
        imOut = Image.fromarray(absoluteDifferenceImage.astype('uint8'))
        signOut = Image.fromarray(imageSign.astype('uint8'))
    else:
        imOut = Image.fromarray(absoluteDifferenceImage[:,:,channel].astype('uint8'))
        signOut = Image.fromarray(imageSign[:,:,channel].astype('uint8'))

    imOut.save(args.firstFile.name + args.secondFile.name + str(channel) + "D.png")
    signOut.save(args.firstFile.name + args.secondFile.name + str(channel) + "S.png")

imInflate.py

#!/usr/bin/python

from PIL import Image
import numpy
import argparse
import os
import sys


#Configure argument parser to take input arguments
parser = argparse.ArgumentParser(description='Expand compressed PNG images. Example ' +
                                             '"imInflate.py 1.png 2.png" takes the ' +
                                             'file 1.png and uses the files ' +
                                             '1.png2.pngxD.png and 1.png2.pngxS.png ' +
                                             'to recreate 2.png  Two images are required ' +
                                             'for each channel of the first file, where x ' +
                                             'in the above example is the channel number ')
parser.add_argument('baseFileName', help='Base Image File')
parser.add_argument('outputFileName', help='Output Image File')
args = parser.parse_args()


#Load base Image
with Image.open(args.baseFileName) as baseImageObject:
    baseImMode = baseImageObject.mode
    if (baseImMode == 'L'):
        baseImage = numpy.asarray(baseImageObject)
        baseImageChannels = 1
    elif (baseImMode == 'P'):
        baseImage = numpy.asarray(baseImageObject.convert('RGBA'))
        baseImageChannels = 4
    elif (baseImMode == 'RGB'):
        baseImage = numpy.asarray(baseImageObject)
        baseImageChannels = 3
    elif (baseImMode == 'RGBA'):
        baseImage = numpy.asarray(baseImageObject)
        baseImageChannels = 4
    else:
        sys.exit("This type of image can't be handled, maybe it is palette based")


#Make base image writeable   
baseImage.setflags(write=True)


print (baseImageChannels)

for channel in range(0,baseImageChannels):
    with Image.open(args.baseFileName + args.outputFileName + str(channel) + "D" + ".png") as diffFile:
        absoluteDifferenceImage = numpy.asarray(diffFile)
    with Image.open(args.baseFileName + args.outputFileName + str(channel) + "S" + ".png") as signFile:
        signImage = numpy.asarray(signFile)

    signMask = (-2*(signImage)//255 + 1)
    differenceImage = numpy.multiply(absoluteDifferenceImage, signMask)
    if (baseImageChannels == 1):
        baseImage = baseImage - differenceImage
        print (numpy.min(baseImage))
    else:
        baseImage[:,:,channel] = baseImage[:,:,channel] - differenceImage

imOut = Image.fromarray(baseImage.astype('uint8'))
imOut.save(args.outputFileName)