Compression Alternatives for Foot Pressure Map

both.json

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FootprintCompression.py

import json

footprint = json.load(open('both.json'))

shape = (44,52)

nonzero = 0
for f in footprint:
    for l in f:
        if l > 0:
            nonzero += 1
print "nonzero:", nonzero

def Plain(footprint):
    payload = []
    payload.extend(shape)
    for row in xrange(shape[0]):
        for col in xrange(shape[1]):
            val = footprint[row][col]
            payload.append(val)
    return payload

def CoordinateList(footprint):
    payload = []
    for row in xrange(shape[0]):
        for col in xrange(shape[1]):
            val = footprint[row][col]
            if val > 0:
                payload.extend((row, col, val))
    return payload

def RunLengthEncoding(footprint):
    payload = []
    for row in xrange(shape[0]):
        line = []
        count = 1
        prev = None
        for col in xrange(shape[1]):
            val = footprint[row][col]
            if val != prev:
                if prev != None:
                    line.extend((count, prev))
                count = 1
                prev = val
            else:
                count += 1
        line.extend((count, val))
        payload.append(len(line))
        payload.extend(line)
    return payload

def ListOfLists(footprint):
    payload = []
    for row, rowval in enumerate(footprint):
        line = []
        for col, colval in enumerate(rowval):
            if colval > 0:
                line.extend((col, colval))
        if line:
            payload.append(row)
            payload.append(len(line))
            payload.extend(line)
    return payload

def CompactedListOfLists(footprint):
    payload = []
    for row, rowval in enumerate(footprint):
        line = []
        colindex = 0
        continuous = []
        for col, colval in enumerate(rowval):
            if colval > 0:                
                continuous.append(colval)
            elif continuous:
                line.append(colindex)
                line.append(len(continuous))
                line.extend(continuous)
                continuous = []
        if line:
            payload.append(row)
            payload.append(len(line))
            payload.extend(line)
    return payload

#=======================================

plain = Plain(footprint)
print 'plain:', len(plain)

coo = CoordinateList(footprint)
print 'coo:', len(coo)

rle = RunLengthEncoding(footprint)
print 'rle:', len(rle)

lil = ListOfLists(footprint)
print 'lil:', len(lil)

clil = CompactedListOfLists(footprint)
print 'clil:', len(clil)
print clil

#=======================================

def RunLengthDecoding(entry):
    buf = list(entry)
    rows = []
    while buf:  
        row = []      
        count = buf.pop(0)
        for n in xrange(count/2):
            amount = buf.pop(0)
            val = buf.pop(0)
            for nn in xrange(amount):
                row.append(val)
        rows.append(row)
    return rows


restored = RunLengthDecoding(rle)

assert(restored == footprint)