pdfminer.six/pdfminer/layout.py

#!/usr/bin/env python
import sys
from sys import maxint as INF
from utils import apply_matrix_norm, apply_matrix_pt
from utils import bsearch, bbox2str, matrix2str
from pdffont import PDFUnicodeNotDefined



##  get_bounds
##
def get_bounds(pts):
    """Compute a maximal rectangle that covers all the points."""
    (x0, y0, x1, y1) = (INF, INF, -INF, -INF)
    for (x,y) in pts:
        x0 = min(x0, x)
        y0 = min(y0, y)
        x1 = max(x1, x)
        y1 = max(y1, y)
    return (x0,y0,x1,y1)

def uniq(objs):
    done = set()
    for obj in objs:
        if obj in done: continue
        done.add(obj)
        yield obj
    return

def csort(objs, key):
    idxs = dict( (obj,i) for (i,obj) in enumerate(objs) )
    return sorted(objs, key=lambda obj:(key(obj), idxs[obj]))

def is_uniq(objs):
    for (i,obj1) in enumerate(objs):
        for obj2 in objs[i+1:]:
            if obj1 == obj2: return False
    return True


##  LAParams
##
class LAParams(object):

    def __init__(self,
                 writing_mode='lr-tb',
                 line_overlap=0.5,
                 char_margin=3.0,
                 line_margin=0.5,
                 word_margin=0.1,
                 all_texts=False):
        self.writing_mode = writing_mode
        self.line_overlap = line_overlap
        self.char_margin = char_margin
        self.line_margin = line_margin
        self.word_margin = word_margin
        self.all_texts = all_texts
        return

    def __repr__(self):
        return ('<LAParams: writing_mode=%r, char_margin=%.1f, line_margin=%.1f, word_margin=%.1f all_texts=%r>' %
                (self.writing_mode, self.char_margin, self.line_margin, self.word_margin, self.all_texts))


##  LTItem
##
class LTItem(object):

    def __init__(self, bbox):
        self.set_bbox(bbox)
        return

    def __repr__(self):
        return ('<item bbox=%s>' % bbox2str(self.bbox))

    def set_bbox(self, (x0,y0,x1,y1)):
        if x1 < x0: (x0,x1) = (x1,x0)
        if y1 < y0: (y0,y1) = (y1,y0)
        self.x0 = x0
        self.y0 = y0
        self.x1 = x1
        self.y1 = y1
        self.width = x1-x0
        self.height = y1-y0
        self.bbox = (x0, y0, x1, y1)
        return

    def is_hoverlap(self, obj):
        assert isinstance(obj, LTItem)
        return obj.x0 <= self.x1 and self.x0 <= obj.x1

    def hdistance(self, obj):
        assert isinstance(obj, LTItem)
        if self.is_hoverlap(obj):
            return 0
        else:
            return min(abs(self.x0-obj.x1), abs(self.x1-obj.x0))

    def hoverlap(self, obj):
        assert isinstance(obj, LTItem)
        if self.is_hoverlap(obj):
            return min(abs(self.x0-obj.x1), abs(self.x1-obj.x0))
        else:
            return 0

    def is_voverlap(self, obj):
        assert isinstance(obj, LTItem)
        return obj.y0 <= self.y1 and self.y0 <= obj.y1

    def vdistance(self, obj):
        assert isinstance(obj, LTItem)
        if self.is_voverlap(obj):
            return 0
        else:
            return min(abs(self.y0-obj.y1), abs(self.y1-obj.y0))

    def voverlap(self, obj):
        assert isinstance(obj, LTItem)
        if self.is_voverlap(obj):
            return min(abs(self.y0-obj.y1), abs(self.y1-obj.y0))
        else:
            return 0


##  LTPolygon
##
class LTPolygon(LTItem):

    def __init__(self, linewidth, pts):
        LTItem.__init__(self, get_bounds(pts))
        self.pts = pts
        self.linewidth = linewidth
        return

    def get_pts(self):
        return ','.join( '%.3f,%.3f' % p for p in self.pts )


##  LTLine
##
class LTLine(LTPolygon):

    def __init__(self, linewidth, p0, p1):
        LTPolygon.__init__(self, linewidth, [p0, p1])
        return


##  LTRect
##
class LTRect(LTPolygon):

    def __init__(self, linewidth, (x0,y0,x1,y1)):
        LTPolygon.__init__(self, linewidth, [(x0,y0), (x1,y0), (x1,y1), (x0,y1)])
        return


##  LTImage
##
class LTImage(LTItem):

    def __init__(self, name, stream, bbox):
        LTItem.__init__(self, bbox)
        self.name = name
        self.stream = stream
        self.srcsize = (stream.get_any(('W', 'Width')),
                        stream.get_any(('H', 'Height')))
        self.imagemask = stream.get_any(('IM', 'ImageMask'))
        self.bits = stream.get_any(('BPC', 'BitsPerComponent'), 1)
        self.colorspace = stream.get_any(('CS', 'ColorSpace'))
        if not isinstance(self.colorspace, list):
            self.colorspace = [self.colorspace]
        return

    def __repr__(self):
        (w,h) = self.srcsize
        return '<image %s %dx%d>' % (self.name, w, h)


##  LTText
##
class LTText(object):

    def __init__(self, text):
        self.text = text
        return

    def __repr__(self):
        return '<text %r>' % self.text

    def is_upright(self):
        return True


##  LTAnon
##
class LTAnon(LTText):

    pass


##  LTChar
##
class LTChar(LTItem, LTText):

    debug = 0

    def __init__(self, matrix, font, fontsize, scaling, rise, cid):
        self.matrix = matrix
        self.font = font
        self.fontsize = fontsize
        self.vertical = font.is_vertical()
        self.adv = font.char_width(cid) * fontsize * scaling
        try:
            text = font.to_unichr(cid)
            assert isinstance(text, unicode), text
        except PDFUnicodeNotDefined:
            text = '?'
        (a,b,c,d,e,f) = self.matrix
        self.upright = (0 < a*d*scaling and b*c <= 0)
        LTText.__init__(self, text)
        # compute the boundary rectangle.
        if self.vertical:
            # vertical
            size = font.get_size() * fontsize
            displacement = (1000 - font.char_disp(cid)) * fontsize * .001
            (_,displacement) = apply_matrix_norm(self.matrix, (0, displacement))
            (dx,dy) = apply_matrix_norm(self.matrix, (size, self.adv))
            (_,_,_,_,tx,ty) = self.matrix
            tx -= dx/2
            ty += displacement + rise
            bbox = (tx, ty+dy, tx+dx, ty)
        else:
            # horizontal
            size = font.get_size() * fontsize
            descent = font.get_descent() * fontsize
            (_,descent) = apply_matrix_norm(self.matrix, (0, descent))
            (dx,dy) = apply_matrix_norm(self.matrix, (self.adv, size))
            (_,_,_,_,tx,ty) = self.matrix
            ty += descent + rise
            bbox = (tx, ty, tx+dx, ty+dy)
        LTItem.__init__(self, bbox)
        return

    def __repr__(self):
        if self.debug:
            return ('<char matrix=%s font=%r fontsize=%.1f bbox=%s adv=%s text=%r>' %
                    (matrix2str(self.matrix), self.font, self.fontsize,
                     bbox2str(self.bbox), self.adv, self.text))
        else:
            return '<char %r>' % self.text

    def get_size(self):
        return max(self.width, self.height)

    def is_vertical(self):
        return self.vertical

    def is_upright(self):
        return self.upright

    
##  LTContainer
##
class LTContainer(LTItem):

    def __init__(self, bbox, objs=None):
        LTItem.__init__(self, bbox)
        if objs:
            self.objs = objs[:]
        else:
            self.objs = []
        return

    def __repr__(self):
        return ('<container %s>' % bbox2str(self.bbox))

    def __iter__(self):
        return iter(self.objs)

    def __len__(self):
        return len(self.objs)

    def add(self, obj):
        self.objs.append(obj)
        return

    def merge(self, container):
        self.objs.extend(container.objs)
        return

    # fixate(): determines its boundery.
    def fixate(self):
        if not self.width and self.objs:
            (bx0, by0, bx1, by1) = (INF, INF, -INF, -INF)
            for obj in self.objs:
                bx0 = min(bx0, obj.x0)
                by0 = min(by0, obj.y0)
                bx1 = max(bx1, obj.x1)
                by1 = max(by1, obj.y1)
            self.set_bbox((bx0, by0, bx1, by1))
        return


##  LTTextLine
##
class LTTextLine(LTContainer):

    def __init__(self, objs):
        LTContainer.__init__(self, (0,0,0,0), objs)
        return

    def __repr__(self):
        return ('<textline %s>' % bbox2str(self.bbox))

    def get_text(self):
        return ''.join( obj.text for obj in self.objs if isinstance(obj, LTText) )

    def find_neighbors(self, plane, ratio):
        raise NotImplementedError

class LTTextLineHorizontal(LTTextLine):

    def __init__(self, objs, word_margin):
        LTTextLine.__init__(self, objs)
        LTContainer.fixate(self)
        objs = []
        x1 = INF
        for obj in csort(self.objs, key=lambda obj: obj.x0):
            if isinstance(obj, LTChar) and word_margin:
                margin = word_margin * obj.width
                if x1 < obj.x0-margin:
                    objs.append(LTAnon(' '))
            objs.append(obj)
            x1 = obj.x1
        self.objs = objs + [LTAnon('\n')]
        return

    def find_neighbors(self, plane, ratio):
        h = ratio*self.height
        return plane.find((self.x0, self.y0-h, self.x1, self.y1+h))
    
class LTTextLineVertical(LTTextLine):

    def __init__(self, objs, word_margin):
        LTTextLine.__init__(self, objs)
        LTContainer.fixate(self)
        objs = []
        y0 = -INF
        for obj in csort(self.objs, key=lambda obj: -obj.y1):
            if isinstance(obj, LTChar) and word_margin:
                margin = word_margin * obj.height
                if obj.y1+margin < y0:
                    objs.append(LTAnon(' '))
            objs.append(obj)
            y0 = obj.y0
        self.objs = objs + [LTAnon('\n')]
        return

    def find_neighbors(self, plane, ratio):
        w = ratio*self.width
        return plane.find((self.x0-w, self.y0, self.x1+w, self.y1))
    

##  LTTextBox
##
##  A set of text objects that are grouped within
##  a certain rectangular area.
##
class LTTextBox(LTContainer):

    def __init__(self, objs):
        LTContainer.__init__(self, (0,0,0,0), objs)
        self.index = None
        return

    def __repr__(self):
        return ('<textbox(%s) %s %r...>' % (self.index, bbox2str(self.bbox), self.get_text()[:20]))

    def get_text(self):
        return ''.join( obj.get_text() for obj in self.objs if isinstance(obj, LTTextLine) )

class LTTextBoxHorizontal(LTTextBox):
    
    def fixate(self):
        LTTextBox.fixate(self)
        self.objs = csort(self.objs, key=lambda obj: -obj.y1)
        return

class LTTextBoxVertical(LTTextBox):

    def fixate(self):
        LTTextBox.fixate(self)
        self.objs = csort(self.objs, key=lambda obj: -obj.x1)
        return


##  LTTextGroup
##
class LTTextGroup(LTContainer):

    def __init__(self, objs):
        assert objs
        LTContainer.__init__(self, (0,0,0,0), objs)
        LTContainer.fixate(self)
        return

class LTTextGroupLRTB(LTTextGroup):
    
    def __init__(self, objs):
        LTTextGroup.__init__(self, objs)
        # reorder the objects from top-left to bottom-right.
        self.objs = csort(self.objs, key=lambda obj: obj.x0+obj.x1-(obj.y0+obj.y1))
        return

class LTTextGroupTBRL(LTTextGroup):
    
    def __init__(self, objs):
        LTTextGroup.__init__(self, objs)
        # reorder the objects from top-right to bottom-left.
        self.objs = csort(self.objs, key=lambda obj: -(obj.x0+obj.x1)-(obj.y0+obj.y1))
        return


##  Plane
##
##  A data structure for objects placed on a plane.
##  Can efficiently find objects in a certain rectangular area.
##  It maintains two parallel lists of objects, each of
##  which is sorted by its x or y coordinate.
##
class Plane(object):

    def __init__(self, objs):
        self.xobjs = []
        self.yobjs = []
        self.idxs = dict( (obj,i) for (i,obj) in enumerate(objs) )
        for obj in objs:
            self.place(obj)
        self.xobjs.sort()
        self.yobjs.sort()
        return

    # place(obj): place an object in a certain area.
    def place(self, obj):
        assert isinstance(obj, LTItem)
        self.xobjs.append((obj.x0, obj))
        self.xobjs.append((obj.x1, obj))
        self.yobjs.append((obj.y0, obj))
        self.yobjs.append((obj.y1, obj))
        return

    # find(): finds objects that are in a certain area.
    def find(self, (x0,y0,x1,y1)):
        i0 = bsearch(self.xobjs, x0)[0]
        i1 = bsearch(self.xobjs, x1)[1]
        xobjs = set( obj for (_,obj) in self.xobjs[i0:i1] )
        i0 = bsearch(self.yobjs, y0)[0]
        i1 = bsearch(self.yobjs, y1)[1]
        yobjs = set( obj for (_,obj) in self.yobjs[i0:i1] )
        xobjs.intersection_update(yobjs)
        return sorted(xobjs, key=lambda obj: self.idxs[obj])


##  guess_wmode
##
def guess_wmode(objs):
    """Guess the writing mode by looking at the order of text objects."""
    xy = tb = lr = 0
    obj0 = None
    for obj1 in objs:
        if obj0 is not None:
            dx = obj1.x0+obj1.x1-(obj0.x0+obj0.x1)
            dy = obj1.y0+obj1.y1-(obj0.y0+obj0.y1)
            if abs(dy) < abs(dx):
                xy += 1
            else:
                xy -= 1
            if 0 < dx:
                lr += 1
            else:
                lr -= 1
            if dy < 0:
                tb += 1
            else:
                tb -= 1
        obj0 = obj1
    if 0 < lr:
        lr = 'lr'
    else:
        lr = 'rl'
    if 0 < tb:
        tb = 'tb'
    else:
        tb = 'bt'
    if 0 < xy:
        return lr+'-'+tb
    else:
        return tb+'-'+lr


##  group_lines
##
def group_lines(groupfunc, objs, findfunc, debug=0):
    """Group LTTextLine objects to form a LTTextBox."""
    plane = Plane(objs)
    groups = {}
    for obj in objs:
        neighbors = findfunc(obj, plane)
        assert obj in neighbors, obj
        members = neighbors[:]
        for obj1 in neighbors:
            if obj1 in groups:
                members.extend(groups.pop(obj1))
        if debug:
            print >>sys.stderr, 'group:', members
        group = groupfunc(list(uniq(members)))
        for obj in members:
            groups[obj] = group
    done = set()
    r = []
    for obj in objs:
        group = groups[obj]
        if group in done: continue
        done.add(group)
        group.fixate()
        r.append(group)
    return r


##  group_boxes
##
def group_boxes(groupfunc, objs0, distfunc, debug=0):
    assert objs0
    objs = objs0[:]
    while 2 <= len(objs):
        mindist = INF
        minpair = None
        objs = csort(objs, key=lambda obj: obj.width*obj.height)
        for i in xrange(len(objs)):
            for j in xrange(i+1, len(objs)):
                d = distfunc(objs[i], objs[j])
                if d < mindist:
                    mindist = d
                    minpair = (objs[i], objs[j])
        assert minpair
        (obj1, obj2) = minpair
        objs.remove(obj1)
        objs.remove(obj2)
        if debug:
            print >>sys.stderr, 'group:', obj1, obj2
        objs.append(groupfunc([obj1, obj2]))
    assert len(objs) == 1
    return objs.pop()


##  LTAnalyzer
##
class LTAnalyzer(LTContainer):

    def analyze(self, laparams):
        """Perform the layout analysis."""
        (textobjs, otherobjs) = self.get_textobjs()
        # textobjs is a list of LTChar objects, i.e.
        # it has all the individual characters in the page.
        if not laparams or not textobjs: return
        if laparams.writing_mode not in ('lr-tb', 'tb-rl'):
            laparams.writing_mode = guess_wmode(textobjs)
        if (laparams.writing_mode.startswith('tb-') or
            laparams.writing_mode.startswith('bt-')):
            # assemble them into vertical rows of text.
            textboxes = self.build_textbox_vertical(textobjs, laparams)
            # turn them into a tree.
            top = self.group_textbox_tb_rl(textboxes, laparams)
        else:
            # assemble them into horizontal rows of text.
            textboxes = self.build_textbox_horizontal(textobjs, laparams)
            # turn them into a tree.
            top = self.group_textbox_lr_tb(textboxes, laparams)
        def assign_index(obj, i):
            if isinstance(obj, LTTextBox):
                obj.index = i
                i += 1
            elif isinstance(obj, LTTextGroup):
                for x in obj:
                    i = assign_index(x, i)
            return i
        assign_index(top, 0)
        textboxes.sort(key=lambda box:box.index)
        self.objs = textboxes + otherobjs
        self.layout = top
        return

    def get_textobjs(self):
        """Split all the objects in the page into text-related objects and others."""
        textobjs = []
        otherobjs = []
        for obj in self.objs:
            if isinstance(obj, LTText) and obj.is_upright():
                textobjs.append(obj)
            else:
                otherobjs.append(obj)
        return (textobjs, otherobjs)

    def build_textbox_horizontal(self, objs, laparams):
        """Identify horizontal text regions in the page."""
        def aligned(obj1, obj2):
            # +------+ - - -
            # | obj1 | - - +------+   -
            # |      |     | obj2 |   | (line_overlap)
            # +------+ - - |      |   -
            #        - - - +------+
            #
            #        |<--->|
            #      (char_margin)
            return ((min(obj1.height, obj2.height) * laparams.line_overlap < obj1.voverlap(obj2)) and
                    (obj1.hdistance(obj2) < min(obj1.width, obj2.width) * laparams.char_margin))
        lines = []
        line = []
        prev = None
        for cur in objs:
            if prev is not None and not aligned(prev, cur):
                if line:
                    lines.append(LTTextLineHorizontal(line, laparams.word_margin))
                    line = []
            line.append(cur)
            prev = cur
        if line:
            lines.append(LTTextLineHorizontal(line, laparams.word_margin))
        return group_lines(LTTextBoxHorizontal, lines, 
                           lambda obj, plane: obj.find_neighbors(plane, laparams.line_margin))
    
    def build_textbox_vertical(self, objs, laparams):
        """Identify vertical text regions in the page."""
        def aligned(obj1, obj2):
            # +------+
            # | obj1 |
            # |      |
            # +------+ - - -
            #   |    |     | (char_margin)
            #   +------+ - -
            #   | obj2 |
            #   |      |
            #   +------+
            #
            #   |<-->|
            # (line_overlap)
            return ((min(obj1.width, obj2.width) * laparams.line_overlap < obj1.hoverlap(obj2)) and
                    (obj1.vdistance(obj2) < min(obj1.height, obj2.height) * laparams.char_margin))
        lines = []
        line = []
        prev = None
        for cur in objs:
            if prev is not None and not aligned(prev, cur):
                if line:
                    lines.append(LTTextLineVertical(line, laparams.word_margin))
                    line = []
            line.append(cur)
            prev = cur
        if line:
            lines.append(LTTextLineVertical(line, laparams.word_margin))
        return group_lines(LTTextBoxVertical, lines,
                           lambda obj, plane: obj.find_neighbors(plane, laparams.line_margin))

    def group_textbox_lr_tb(self, boxes, laparams):
        def dist(obj1, obj2):
            """A distance function between two TextBoxes.
            
            Consider the bounding rectangle for obj1 and obj2.
            Return its area less the areas of obj1 and obj2, 
            shown as 'www' below. This value may be negative.
            +------+..........+
            | obj1 |wwwwwwwwww:
            +------+www+------+
            :wwwwwwwwww| obj2 |
            +..........+------+
            """
            return ((max(obj1.x1,obj2.x1) - min(obj1.x0,obj2.x0)) * 
                    (max(obj1.y1,obj2.y1) - min(obj1.y0,obj2.y0)) -
                    (obj1.width*obj1.height + obj2.width*obj2.height))
        return group_boxes(LTTextGroupLRTB, boxes, dist)

    def group_textbox_tb_rl(self, boxes, laparams):
        def dist(obj1, obj2):
            return ((max(obj1.x1,obj2.x1) - min(obj1.x0,obj2.x0)) *
                    (max(obj1.y1,obj2.y1) - min(obj1.y0,obj2.y0)) -
                    (obj1.width*obj1.height + obj2.width*obj2.height))
        return group_boxes(LTTextGroupTBRL, boxes, dist)
    

##  LTFigure
##
class LTFigure(LTAnalyzer):

    def __init__(self, name, bbox, matrix):
        (x,y,w,h) = bbox
        bbox = get_bounds( apply_matrix_pt(matrix, (p,q))
                           for (p,q) in ((x,y), (x+w,y), (x,y+h), (x+w,y+h)) )
        LTAnalyzer.__init__(self, bbox)
        self.name = name
        self.matrix = matrix
        return

    def __repr__(self):
        return ('<figure %r bbox=%s matrix=%s>' %
                (self.name, bbox2str(self.bbox), matrix2str(self.matrix)))

    def analyze(self, laparams):
        if laparams and laparams.all_texts:
            LTAnalyzer.analyze(self, laparams)
        return


##  LTPage
##
class LTPage(LTAnalyzer):

    def __init__(self, pageid, bbox, rotate=0):
        LTAnalyzer.__init__(self, bbox)
        self.pageid = pageid
        self.rotate = rotate
        self.layout = None
        return

    def __repr__(self):
        return ('<page(%r) bbox=%s rotate=%r>' % (self.pageid, bbox2str(self.bbox), self.rotate))