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afm.py

00001 """
This is a python interface to Adobe Font Metrics Files.  Although a
number of other python implementations exist (and may be more complete
than mine) I decided not to go with them because either they were
either

  1) copyighted or used a non-BSD compatible license

  2) had too many dependencies and I wanted a free standing lib

  3) Did more than I needed and it was easier to write my own than
     figure out how to just get what I needed from theirs

It is pretty easy to use, and requires only built-in python libs

    >>> from afm import AFM
    >>> fh = file('ptmr8a.afm')
    >>> afm = AFM(fh)
    >>> afm.string_width_height('What the heck?')
    (6220.0, 683)
    >>> afm.get_fontname()
    'Times-Roman'
    >>> afm.get_kern_dist('A', 'f')
    0
    >>> afm.get_kern_dist('A', 'y')
    -92.0
    >>> afm.get_bbox_char('!')
    [130, -9, 238, 676]
    >>> afm.get_bbox_font()
    [-168, -218, 1000, 898]


AUTHOR:
  John D. Hunter <jdhunter@ace.bsd.uchicago.edu>
"""


import sys, os

#Convert string the a python type
_to_int = int
_to_float = float
_to_str =  str

def _to_list_of_ints(s):
    s = s.replace(',', ' ')
    return [_to_int(val) for val in s.split()]

def _to_list_of_floats(s):
    return [_to_float(val) for val in s.split()]
def _to_bool(s):
    if s.lower().strip() in ('false', '0', 'no'): return False
    else: return True


    
00057 def _parse_header(fh):
    """
    Reads the font metrics header (up to the char metrics) and returns
    a dictionary mapping key to val.  val will be converted to the
    appropriate python type as necessary; eg 'False'->False, '0'->0,
    '-168 -218 1000 898'-> [-168, -218, 1000, 898]

    Dictionary keys are

      StartFontMetrics, FontName, FullName, FamilyName, Weight,
      ItalicAngle, IsFixedPitch, FontBBox, UnderlinePosition,
      UnderlineThickness, Version, Notice, EncodingScheme, CapHeight,
      XHeight, Ascender, Descender, StartCharMetrics

    """
    headerConverters = {
        'StartFontMetrics': _to_float,
        'FontName': _to_str,
        'FullName': _to_str,
        'FamilyName': _to_str,
        'Weight': _to_str,
        'ItalicAngle': _to_float,
        'IsFixedPitch': _to_bool,
        'FontBBox': _to_list_of_ints,
        'UnderlinePosition': _to_int,
        'UnderlineThickness': _to_int,
        'Version': _to_str,
        'Notice': _to_str,
        'EncodingScheme': _to_str,
        'CapHeight': _to_float,
        'XHeight': _to_float,
        'Ascender': _to_float,
        'Descender': _to_float,
        'StdHW': _to_float,
        'StdVW': _to_float,
        'StartCharMetrics': _to_int,
        'CharacterSet': _to_str,
        'Characters': _to_int,
        'Capheight': _to_int,
        }

    d = {}
    while 1:
        line = fh.readline()
        if not line: break
        line = line.rstrip()
        if line.startswith('Comment'): continue
        lst = line.split( ' ', 1 )
        #print '%-s\t%-d line :: %-s' % ( fh.name, len(lst), line )
        key = lst[0]
        if len( lst ) == 2:
           val = lst[1]
        else:
           val = ''
        #key, val = line.split(' ', 1)
        try: d[key] = headerConverters[key](val)
        except ValueError: 
            print >>sys.stderr, 'Value error parsing header in AFM:', key, val
            continue
        except KeyError: 
            print >>sys.stderr, 'Found an unknown keyword in AFM header (was %s)' % key
            continue
        if key=='StartCharMetrics': return d
    raise RuntimeError('Bad parse')

00122 def _parse_char_metrics(fh):
    """
    Return a character metric dictionary.  Keys are the ASCII num of
    the character, values are a (wx, name, bbox) tuple, where

      wx is the character width
      name is the postscript language name
      bbox (llx, lly, urx, ury)

    This function is incomplete per the standard, but thus far parse
    all the sample afm files I have
    """

    d = {}
    while 1:
        line = fh.readline()
        if not line: break
        line = line.rstrip()
        if line.startswith('EndCharMetrics'): return d
        vals = line.split(';')[:4]
        if len(vals) !=4 : raise RuntimeError('Bad char metrics line: %s' % line)
        num = _to_int(vals[0].split()[1])
        wx = _to_float(vals[1].split()[1])
        name = vals[2].split()[1]
        bbox = _to_list_of_ints(vals[3][2:])
        # Workaround: If the character name is 'Euro', give it the corresponding 
        # character code, according to WinAnsiEncoding (see PDF Reference).
        if name == 'Euro':
            num = 128
        if num != -1:
            d[num] = (wx, name, bbox)
    raise RuntimeError('Bad parse')

00155 def _parse_kern_pairs(fh):
    """
    Return a kern pairs dictionary; keys are (char1, char2) tuples and
    values are the kern pair value.  For example, a kern pairs line like

      KPX A y -50

    will be represented as

      d[ ('A', 'y') ] = -50

    """

    line = fh.readline()
    if not line.startswith('StartKernPairs'):
        raise RuntimeError('Bad start of kern pairs data: %s'%line)
    
    d = {}
    while 1:
        line = fh.readline()
        if not line: break
        line = line.rstrip()
        if len(line)==0: continue
        if line.startswith('EndKernPairs'):
            fh.readline()  # EndKernData
            return d
        vals = line.split()
        if len(vals)!=4 or vals[0]!='KPX':
            raise RuntimeError('Bad kern pairs line: %s'%line)        
        c1, c2, val = vals[1], vals[2], _to_float(vals[3])
        d[(c1,c2)] = val
    raise RuntimeError('Bad kern pairs parse')

00188 def _parse_composites(fh):
    """
    Return a composites dictionary.  Keys are the names of the
    composites.  vals are a num parts list of composite information,
    with each element being a (name, dx, dy) tuple.  Thus if a
    composites line reading:

      CC Aacute 2 ; PCC A 0 0 ; PCC acute 160 170 ;

    will be represented as

      d['Aacute'] = [ ('A', 0, 0), ('acute', 160, 170) ]
      
    """
    d = {}
    while 1:
        line = fh.readline()
        if not line: break
        line = line.rstrip()
        if len(line)==0: continue
        if line.startswith('EndComposites'):
            return d
        vals = line.split(';')
        cc = vals[0].split()
        name, numParts = cc[1], _to_int(cc[2])
        pccParts = []
        for s in vals[1:-1]:
            pcc = s.split()
            name, dx, dy = pcc[1], _to_float(pcc[2]), _to_float(pcc[3])
            pccParts.append( (name, dx, dy) )
        d[name] = pccParts

    raise RuntimeError('Bad composites parse')

00222 def _parse_optional(fh):
    """
    Parse the optional fields for kern pair data and composites

    return value is a kernDict, compositeDict which are the return
    values from parse_kern_pairs, and parse_composites if the data
    exists, or empty dicts otherwise
    """
    optional = {
        'StartKernData' : _parse_kern_pairs,
        'StartComposites' :  _parse_composites,
        }

    d = {'StartKernData':{}, 'StartComposites':{}}
    while 1:
        line = fh.readline()
        if not line: break
        line = line.rstrip()
        if len(line)==0: continue
        key = line.split()[0]
        
        if optional.has_key(key): d[key] = optional[key](fh)

    l = ( d['StartKernData'], d['StartComposites'] )
    return l
    
00248 def parse_afm(fh):
    """
    Parse the Adobe Font Metics file in file handle fh
    Return value is a (dhead, dcmetrics, dkernpairs, dcomposite) tuple where

    dhead : a parse_header dict
    dcmetrics :  a parse_composites dict
    dkernpairs : a parse_kern_pairs dict, possibly {}
    dcomposite : a parse_composites dict , possibly {}
    """
    dhead =  _parse_header(fh)
    dcmetrics =  _parse_char_metrics(fh)
    doptional = _parse_optional(fh)
    return dhead, dcmetrics, doptional[0], doptional[1]


class AFM:

    def __init__(self, fh):
        """
        Parse the AFM file in file object fh
        """
        (dhead, dcmetrics, dkernpairs, dcomposite) = parse_afm(fh)
        self._header = dhead
        self._kern = dkernpairs
        self._metrics = dcmetrics
        self._composite = dcomposite


    def get_bbox_char(self, c, isord=False):
        if not isord: c=ord(c)
        wx, name, bbox = self._metrics[c]
        return bbox
    
    def string_width_height(self, s):
        """
        Return the string width (including kerning) and string height
        as a w,h tuple
        """
        if not len(s): return 0,0
        totalw = 0
        namelast = None
        miny = 1e9
        maxy = 0
        for c in s:
            if c == '\n': continue
            wx, name, bbox = self._metrics[ord(c)]
            l,b,w,h = bbox
            
            # find the width with kerning
            try: kp = self._kern[ (namelast, name) ]
            except KeyError: kp = 0
            totalw += wx + kp
            
            # find the max y
            thismax = b+h
            if thismax>maxy: maxy = thismax

            # find the min y
            thismin = b
            if thismin<miny: miny = thismin

        return totalw, maxy-miny

    def get_str_bbox(self, s):
        """
        Return the string bounding box
        """
        if not len(s): return 0,0,0,0
        totalw = 0
        namelast = None
        miny = 1e9
        maxy = 0
        left = 0
        for c in s:
            if c == '\n': continue
            wx, name, bbox = self._metrics[ord(c)]
            l,b,w,h = bbox
            if l<left: left = l
            # find the width with kerning
            try: kp = self._kern[ (namelast, name) ]
            except KeyError: kp = 0
            totalw += wx + kp
            
            # find the max y
            thismax = b+h
            if thismax>maxy: maxy = thismax

            # find the min y
            thismin = b
            if thismin<miny: miny = thismin

        return left, miny, totalw, maxy-miny


    def get_name_char(self, c):
        """
        Get the name of the character, ie, ';' is 'semicolon'
        """
        wx, name, bbox = self._metrics[ord(c)]
        return name

    def get_width_char(self, c, isord=False):
        """
        Get the width of the character from the character metric WX
        field
        """
        if not isord: c=ord(c)
        wx, name, bbox = self._metrics[c]
        return wx

    def get_height_char(self, c, isord=False):
        """
        Get the height of character c from the bounding box.  This is
        the ink height (space is 0)
        """
        if not isord: c=ord(c)
        wx, name, bbox = self._metrics[c]
        return bbox[-1]

    def get_kern_dist(self, c1, c2):
        """
        Return the kerning pair distance (possibly 0) for chars c1 and
        c2
        """
        name1, name2 = self.get_name_char(c1), self.get_name_char(c2)
        try: return self._kern[ (name1, name2) ]
        except: return 0        

    def get_fontname(self):
        "Return the font name, eg, Times-Roman"
        return self._header['FontName']

    def get_fullname(self):
        "Return the font full name, eg, Times-Roman"
        return self._header['FullName']

    def get_familyname(self):
        "Return the font family name, eg, Times"
        return self._header['FamilyName']
    
    def get_weight(self):
        "Return the font weight, eg, 'Bold' or 'Roman'"
        return self._header['Weight']

    def get_angle(self):
        "Return the fontangle as float"
        return self._header['ItalicAngle']



if __name__=='__main__':
    #pathname = '/usr/local/lib/R/afm/'
    pathname = '/usr/local/share/fonts/afms/adobe'

    for fname in os.listdir(pathname):
        fh = file(os.path.join(pathname,fname))
        afm = AFM(fh)
        w,h =  afm.string_width_height('John Hunter is the Man!')


            

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