Original Photoshop ACV File Reader Python Code from (Now-Defunct) WeemoApps.com

original-photoshop-acv-reader.py

#!/usr/bin/env python
"""
DESCRIPTION

    Prints the polynomials that describe a photoshop curve.
    There are three curves (one per RGB channel) which you can later
    use to make a custom filter for your image.

    See http://www.weemoapps.com/creating-retro-and-analog-image-filters-in-mobile-apps
    for the theory behind this method.

USAGE

    python extractCurvesFromACVFile.py theCurveFile.acv

    You need to have scipy and numpy installed.

AUTHOR

    email: [email protected]
    twitter: @weemoapps

LICENSE

    Do whatever you want, but please mention this code in your code if you modify it.

VERSION

    0.1
"""

import sys, os, traceback, optparse, time
from struct import unpack
from scipy import interpolate
import numpy as np

#Here we read the .acv curve file. It will help to take a look at see the link below to lean about the .acv file format specifications
# http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/PhotoshopFileFormats.htm#50577411_pgfId-1056330
def read_curve(acv_file):
    curve = []
    number_of_points_in_curve, = unpack("!h", acv_file.read(2))
    for j in range(number_of_points_in_curve):
        y, x = unpack("!hh", acv_file.read(4))
        curve.append((x, y))
    return curve

#Here we do the interpolation in order to get a curve out of the curve points we already have.
def return_polynomial_coefficients(curve_list):
    xdata = [x[0] for x in curve_list]
    ydata = [x[1] for x in curve_list]
    np.set_printoptions(precision=6)
    np.set_printoptions(suppress=True)
    p = interpolate.lagrange(xdata, ydata)
    
    coefficients = p.c
    print coefficients
    
    return p

def main():
    if (len(sys.argv) != 1):
        acv_file = open(sys.argv[1], "rb")
    else:
        print "Wrong args. Usage: python extractCurvesFromACVFile.py curveFile.acv"
        os._exit(1)

    _, nr_curves = unpack("!hh", acv_file.read(4))
    curves = []
    for i in range(nr_curves):
        curves.append(read_curve(acv_file))
    compositeCurve = curves[0]
    redCurve = curves[1]
    greenCurve = curves[2]
    blueCurve = curves[3]

    print "************* Red Curve *************"
    print ""
    pRed = return_polynomial_coefficients(redCurve)
    print pRed
    print ""
    print "*************************************\n"
    print ""

    print "************* Green Curve *************"
    print ""
    pGreen = return_polynomial_coefficients(greenCurve)
    print pGreen
    print ""
    print "***************************************\n"
    print ""

    print "************* Blue Curve *************"
    print ""
    pBlue = return_polynomial_coefficients(blueCurve)
    print pBlue
    print ""
    print "**************************************\n"
    print ""

if __name__ == '__main__':
    try:
        sys.argv.append(
            '/Users/fish/Praxa/django-instakit/instance/django_instakit/static/django_instakit/acv/country.acv')
        
        main()
    except Exception, e:
        print 'ERROR, UNEXPECTED EXCEPTION'
        print str(e)
        traceback.print_exc()
        os._exit(1)

Adapted into a part of InstaKit, q.v. source of instakit.processors.curves