lsb-imagepick.py

#!/usr/bin/python
# -*- coding: utf8 -*-
"""
SYNOPSIS

Pick specified pixels from an image and create a new image with that pixels

DESCRIPTION

    

EXAMPLES

    

EXIT STATUS

    

AUTHOR

    luca.mella@studio.unibo.it

LICENSE

    Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)

VERSION

    0.4
"""

from PIL import Image
import re
from optparse import OptionParser


def impick(n,channels,period,vert):
    """ Pick image pixel periodically """
    n = n.convert('RGBA')
    nn = Image.new( n.mode, n.size, "black")
    m = n.load()
    s = n.size
    #nn = nn.convert('RGBA')
    mm = nn.load()
    if vert:
        xmax=s[1]
        ymax=s[0]
    else:
        xmax=s[0]
        ymax=s[1]

    xmin=0
    step=1
    for x in range(xmin,xmax,step):
        for y in range(ymax):
            r,g,b,a = m[(x,y)]
            r1,g1,b1,a1 = 0,0,0,255
            if (y % period == 0):
                if 'r' in channels :
                     r1=r
                if 'g' in channels :
                     g1=g
                if 'b' in channels :
                     b1=b
                if 'a' in channels :
                     a1=a
            mm[(x,y)]=r1,g1,b1,a1
    return nn
#-------------------------------------------------------------------------------
# MAIN 
#-------------------------------------------------------------------------------
if __name__ == "__main__":
    
    parser = OptionParser("usage: %prog [OPTIONS] ARGS \nDefault output in STDOUT")
    parser.add_option("-f", "--file", dest="filename", action="store", type="string",
                      help="image where to read pixels", metavar="FILE")
    parser.add_option("-v", "--vertical", dest="vertical", action="store_true", 
                      help="Shift in vertical direction (Y)", metavar="VERTICAL")
    parser.add_option("-p", "--period", dest="period", action="store", type="int", default=1,
                      help="Specify the which line will shift, eg. 2 means once on two", metavar="PERIOD")
    parser.add_option("-c", "--channel",dest="channel", action="store", type="string",
                      default='rgb',help="channel to consider [r][g][b][a].", metavar="CHANNEL")

    (options, args) = parser.parse_args()

    if options.filename == None :
        parser.error("Input image is mandatory!")

    mtch = re.compile('[a|r|g|b]{1,4}').match(options.channel.lower())

    if mtch is None :
        print 'ERROR: invalid channel specification'
        exit(-1)

    inputim = options.filename
    channels = mtch.group()
    vert=options.vertical
    period= options.period

    outim=inputim+"-pick"+str(period)+"-"+channels+".png"
    
    n = Image.open(inputim)

    nn=impick(n,channels,period,vert)

    print 'Writing output to file: %s' %(outim)
    nn.save(outim, "PNG")