Monkeypatch reportlab to output grayscale and monochrome colorspaces
This commit is contained in:
Jim Barlow
+104
-20
@@ -6,12 +6,95 @@
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# Initial version by Jonathan Brinley, jonathanbrinley@gmail.com
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##############################################################################
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from reportlab.pdfgen.canvas import Canvas
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from reportlab.pdfgen.pdfimages import PDFImage
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from reportlab.lib.units import inch
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from lxml import etree as ElementTree
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from PIL import Image
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import re, sys
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import argparse
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def monkeypatch_method(cls):
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'''
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Override a class method at runtime.
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Rationale:
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https://mail.python.org/pipermail/python-dev/2008-January/076194.html
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'''
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def decorator(func):
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setattr(cls, func.__name__, func)
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return func
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return decorator
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@monkeypatch_method(PDFImage)
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def PIL_imagedata(self):
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'''
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Add ability to output greyscale and 1-bit PIL images without conversion to RGB.
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The upstream Python 2.7 version of reportlab converts 1-bit PIL images to RGB
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instead of saving them in a lower BPP format. They have since added the following
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fix to their Python 3.3 branch, but it has not been back-ported.
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https://bitbucket.org/rptlab/reportlab/commits/177ddcbe4df6f9b461dac62612df9b8da3966a5d
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'''
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image = self.image
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if image.format == 'JPEG':
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fp = image.fp
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fp.seek(0)
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return self._jpg_imagedata(fp)
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from reportlab.lib.utils import import_zlib
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from reportlab import rl_config
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from reportlab.pdfbase.pdfutils import _AsciiBase85Encode, _chunker
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self.source = 'PIL'
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zlib = import_zlib()
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if not zlib:
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return
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bpc = 8
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# Use the colorSpace in the image
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if image.mode == 'CMYK':
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myimage = image
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colorSpace = 'DeviceCMYK'
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bpp = 4
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elif image.mode == '1':
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myimage = image
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colorSpace = 'DeviceGray'
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bpp = 1
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bpc = 1
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elif image.mode == 'L':
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myimage = image
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colorSpace = 'DeviceGray'
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bpp = 1
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else:
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myimage = image.convert('RGB')
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colorSpace = 'RGB'
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bpp = 3
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imgwidth, imgheight = myimage.size
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# this describes what is in the image itself
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# *NB* according to the spec you can only use the short form in inline images
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imagedata = ['BI /W %d /H %d /BPC %d /CS /%s /F [%s/Fl] ID' %
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(imgwidth, imgheight, bpc, colorSpace, rl_config.useA85 and '/A85 ' or '')]
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# use a flate filter and, optionally, Ascii Base 85 to compress
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raw = myimage.tostring()
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rowstride = (imgwidth * bpc * bpp + 7) / 8
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assert len(raw) == rowstride * imgheight, "Wrong amount of data for image"
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data = zlib.compress(raw) # this bit is very fast...
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if rl_config.useA85:
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# ...sadly this may not be
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data = _AsciiBase85Encode(data)
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# append in blocks of 60 characters
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_chunker(data, imagedata)
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imagedata.append('EI')
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return (imagedata, imgwidth, imgheight)
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class hocrTransform():
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"""
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A class for converting documents from the hOCR format.
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@@ -24,20 +107,20 @@ class hocrTransform():
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self.hocr = ElementTree.ElementTree()
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self.hocr.parse(hocrFileName)
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# if the hOCR file has a namespace, ElementTree requires its use to find elements
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matches = re.match('({.*})html', self.hocr.getroot().tag)
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self.xmlns = ''
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if matches:
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self.xmlns = matches.group(1)
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# get dimension in pt (not pixel!!!!) of the OCRed image
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for div in self.hocr.findall(".//%sdiv[@class='ocr_page']"%(self.xmlns)):
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coords = self.element_coordinates(div)
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self.width = self.px2pt(coords[2]-coords[0])
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self.height = self.px2pt(coords[3]-coords[1])
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break # there shouldn't be more than one, and if there is, we don't want it
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# no width and heigh definition in the ocr_image element of the hocr file
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if self.width is None:
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print("No page dimension found in the hocr file")
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@@ -54,7 +137,7 @@ class hocrTransform():
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return self._get_element_text(body).encode('utf-8') # XML gives unicode
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else:
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return ''
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def _get_element_text(self, element):
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"""
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Return the textual content of the element and its children
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@@ -67,7 +150,7 @@ class hocrTransform():
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if element.tail is not None:
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text = text + element.tail
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return text
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def element_coordinates(self, element):
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"""
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Returns a tuple containing the coordinates of the bounding box around
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@@ -80,13 +163,13 @@ class hocrTransform():
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coords = matches.group(1).split()
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out = (int(coords[0]),int(coords[1]),int(coords[2]),int(coords[3]))
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return out
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def px2pt(self, pxl):
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"""
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Returns the length in pt given length in pxl
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"""
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return float(pxl)/self.dpi*inch
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def to_pdf(self, outFileName, imageFileName, showBoundingboxes, fontname="Helvetica"):
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"""
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Creates a PDF file with an image superimposed on top of the text.
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@@ -97,13 +180,13 @@ class hocrTransform():
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"""
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# create the PDF file
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pdf = Canvas(outFileName, pagesize=(self.width, self.height), pageCompression=1) # page size in points (1/72 in.)
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# draw bounding box for each paragraph
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pdf.setStrokeColorRGB(0,1,1) # light blue for bounding box of paragraph
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pdf.setFillColorRGB(0,1,1) # light blue for bounding box of paragraph
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pdf.setLineWidth(0) # no line for bounding box
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for elem in self.hocr.findall(".//%sp[@class='%s']" % (self.xmlns, "ocr_par")):
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elemtxt=self._get_element_text(elem).rstrip()
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if len(elemtxt) == 0:
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continue
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@@ -113,12 +196,12 @@ class hocrTransform():
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y1=self.px2pt(coords[1])
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x2=self.px2pt(coords[2])
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y2=self.px2pt(coords[3])
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# draw the bbox border
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if showBoundingboxes == True:
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pdf.rect(x1, self.height-y2, x2-x1, y2-y1, fill=1)
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pdf.rect(x1, self.height-y2, x2-x1, y2-y1, fill=1)
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# check if element with class 'ocrx_word' are available
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# otherwise use 'ocr_line' as fallback
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elemclass="ocr_line"
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@@ -141,7 +224,7 @@ class hocrTransform():
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y1=self.px2pt(coords[1])
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x2=self.px2pt(coords[2])
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y2=self.px2pt(coords[3])
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# draw the bbox border
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if showBoundingboxes == True:
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pdf.rect(x1, self.height-y2, x2-x1, y2-y1, fill=0)
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@@ -152,7 +235,7 @@ class hocrTransform():
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# set cursor to bottom left corner of bbox (adjust for dpi)
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text.setTextOrigin(x1, self.height-y2)
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# scale the width of the text to fill the width of the bbox
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text.setHorizScale(100*(x2-x1)/pdf.stringWidth(elemtxt, fontname, fontsize))
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@@ -162,13 +245,14 @@ class hocrTransform():
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# put the image on the page, scaled to fill the page
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if imageFileName != None:
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im = Image.open(imageFileName)
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im = Image.open(imageFileName)
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pdf.drawInlineImage(im, 0, 0, width=self.width, height=self.height)
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# finish up the page and save it
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pdf.showPage()
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pdf.save()
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if __name__ == "__main__":
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parser = argparse.ArgumentParser(description='Convert hocr file to PDF')
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parser.add_argument('-b', '--boundingboxes', action="store_true", default=False, help='Show bounding boxes borders')
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@@ -181,5 +265,5 @@ if __name__ == "__main__":
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hocr = hocrTransform(args.hocrfile, args.resolution)
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hocr.to_pdf(args.outputfile, args.image, args.boundingboxes)
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