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djvusededitor.py
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djvusededitor.py
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#!/usr/bin/env python3
import re
from sly import Lexer, Parser
import sys, os, re
from math import sqrt
from typing import Callable
# Try using: github.com/sarnold/pdfrw as it contains many fixes compared to pmaupin's version
from pdfrw import PdfReader, PdfWriter, PdfArray, PdfDict, IndirectPdfDict, PdfName
from .common import err,msg,warn,eprint, encapsulate
from .pdffont import PdfFont, PdfTextString, PdfFontUtils
from .pdffontencoding import PdfFontEncoding
from .pdfstreamparser import PdfStream
from .pdfstreameditor import PdfStreamEditor
from .djvusedparser import DjVuSedLexer, DjVuSedParser
from .pdfstate import PdfState
from .pdffontglyphmap import PdfFontGlyphMap
from .pdffilter import PdfFilter
import xml.etree.ElementTree as ET # for parsing hOCR files
# ========================================================================== class DjVuSedEditor
class DjVuSedEditor:
def __init__(self, djvuSedStream:str):
'''Parses the djvuSedStream and stores the resulting djvused page tree in self.tree'''
self.stream = djvuSedStream
lexer,parser = DjVuSedLexer(),DjVuSedParser()
tokens = lexer.tokenize(self.stream)
# for tok in tokens: print(tok)
# sys.exit()
self.tree = parser.parse(tokens)
# pprint.pprint(self.tree)
# sys.exit()
def djvuSedStringToUnicode(self, djvuSedString:str):
'''Convert an ASCII-encoded string from a djvused stream to a Unicode string
'''
s = djvuSedString
if len(s) < 2 or s[0] != '"' or s[-1] != '"': err(f'invalid stirng: {s}')
return s[1:-1].encode('latin1').decode('unicode-escape').encode('latin1').decode('utf-8')
def unicodeToDjvuSedString(self, unicodeStr:str):
'''Convert a Unicode string to am ASCII-encoded string (non-ASCII chars are octal-escaped as \\123)
to be used in a djvused stream
'''
# return ''.join(chr(b) if b<128 and b>=32 and b!=134 and b!=42 else f'\\{b:o}' for b in unicodeStr.encode('utf-8'))
# No idea why the "and b!=134 and b!=42" part was inserted
return ''.join(chr(b) if b<128 and b>=32 else f'\\{b:o}' for b in unicodeStr.encode('utf-8'))
# def djvusedPageTreeToPDFStream(self, djvusedPageTree:list, font:PdfFont, fontsize = None, baseline_y = None, debug = False):
def djvusedPageTreeToPDFStream(self, djvusedPageTree:list, font:PdfFont, baseline_y = None, scale_y = None):
'''Convert annotations in the parsed djvusedPageTree to a PDF stream.
The djvusedPageTree can be an arbitrary set of annotation commands that relates to a single page, that is
anything between two consecutive "select pageNo" commands in the original djvused stream.'''
stream = ''
for chunk in djvusedPageTree:
if len(chunk) != 6: err(f'set-txt chunk has #elements != 6: {chunk}')
type,xmin,ymin,xmax,ymax,text = chunk # note that always ymax < ymin, this is just bad naming
if type == 'line':
baseline_y = int(round(0.2*(4*int(ymax) + 1*int(ymin))))
scale_y = int(ymin)- int(ymax)
if isinstance(text,str) and len(text)>0:
textNormalized = text
textNormalized = self.unicodeToDjvuSedString(text) # This extends djvused format to allow Unicode strings
textUnicode = self.djvuSedStringToUnicode(textNormalized)
if len(textUnicode) == 0: continue
pdfString = font.encodePdfTextString(textUnicode)
stringWidth = font.width(textUnicode)
if stringWidth == 0: continue
scale_x = int(round(float(xmax)-float(xmin))/stringWidth)
# if fontsize != None and fontsize_new > fontsize and len(textUnicode)<3:
# fontsize_new = fontsize
if baseline_y == None: baseline_y = int(round(0.2*(4*int(ymax) + 1*int(ymin))))
if scale_y == None: scale_y = int(ymin)-int(ymax)
# stream += f'BT /OCR {fontsize_new} Tf {xmin} {baseline_y:.1f} Td {invisible}{hexString} Tj ET\n'
stream += f'{scale_x} 0 0 {scale_y} {xmin} {baseline_y} Tm {pdfString} Tj\n'
# if len(textUnicode)>=5: fontsize = fontsize_new
elif isinstance(text,list):
# if type == 'line': # test run to determine fontsize
# streamDelta,fontsize = self.djvusedPageTreeToPDFStream(chunk[5],font,None,baseline_y,debug)
# streamDelta,fontsize = self.djvusedPageTreeToPDFStream(chunk[5],font,fontsize,baseline_y,debug)
# stream += streamDelta
stream += self.djvusedPageTreeToPDFStream(chunk[5], font, baseline_y, scale_y)
elif text is None:
continue
else:
err('set-txt: chunk\'s last element is neither of: string/list/None: {chunk}')
# return stream, fontsize
return stream
def insert_ocr(self, pdf:PdfReader, defaultUnicodeFont:str, defaultFontDir:str, firstPage = 1, debug = False):
# One font, many pages
utils = PdfFontUtils()
font = utils.loadFont([defaultUnicodeFont], ['.',defaultFontDir])
if not font: raise ValueError(f'cannot proceed with inserting an OCR layer: no font loaded')
xobjCache = {}
# Run over pages in the djvusedTree
for djvusedPage in self.tree:
if djvusedPage[0] == 'save': continue
if djvusedPage[0] != 'select': err(f'expected select, got: {djvusedPage[0]}')
try: pageNo = int(djvusedPage[1]) + firstPage - 1
except: pageNo = firstPage
if pageNo < 1 or pageNo > len(pdf.pages):
err(f'pageNo ({pageNo}) is outside pdf page range (1-{len(pdf.pages)})')
eprint(f'inserting OCR in page {pageNo}')
pdfPage = pdf.pages[pageNo-1]
# Fix missing Contents
if pdfPage.Contents == None:
pdfPage.Contents = IndirectPdfDict(stream = '')
# Remove old OCR
resources = pdfPage.inheritable.Resources
if resources == None: resources = PdfDict(); pdfPage.Resources = resources
pdfEditor = PdfStreamEditor(pdfPage, PdfFontGlyphMap())
pdfEditor.processText(xobjCache=xobjCache, options={'removeOCR':True})
djvusedPageCommands = djvusedPage[2:]
ocrStream = None
for djvusedCmd in djvusedPageCommands:
# assert syntax
if djvusedCmd[0] != 'set-txt': continue
djvusedPageTree = djvusedCmd[1]
if djvusedPageTree[0] != 'page': err('argument of set-txt should be a single page chunk')
# Get the stream
# ocrStream,fontsize = self.djvusedPageTreeToPDFStream([djvusedPageTree],font,None,None,debug)
invisible = '' if debug else ' 3 Tr'
ocrStream = f'BT /OCR 1 Tf{invisible}\n' + self.djvusedPageTreeToPDFStream([djvusedPageTree],font,None,None) + 'ET\n'
# Get the scale factors
xmin,ymin,xmax,ymax = [float(a) for a in djvusedPageTree[1:5]]
width,height = xmax - xmin, ymax - ymin
bbox = pdfPage.inheritable.CropBox or pdfPage.inheritable.MediaBox
if bbox == None: err(f'No page bbox on page {pageNo}')
x1,y1,x2,y2 = [float(b) for b in bbox]
if pdfPage.inheritable.Rotate in ['90','270']:
sx,sy = (x2-x1)/height,(y2-y1)/width
else:
sx,sy = (x2-x1)/width,(y2-y1)/height
break
if ocrStream == None: warn('no set-text command after select') ; continue
# Set up a font to be used for the OCR layer
font.install(pdfPage,'OCR', overwrite=True)
# Write the geometry part of the OCR PDF stream header; account for pdf page rotations
# TEST THIS MORE !!!!
ocrHeader = f'q 1 0 0 1 {x1} {y1} cm\n{sx} 0 0 {sy} 0 0 cm\n'
if pdfPage.inheritable.Rotate == '270': ocrHeader += f'0 -1 1 0 0 {width} cm\n'
if pdfPage.inheritable.Rotate == '180': ocrHeader += f'-1 0 0 -1 {width} {height} cm\n'
if pdfPage.inheritable.Rotate == '90': ocrHeader += f'0 1 -1 0 {height} 0 cm\n'
ocrHeader += f'1 0 0 1 {-xmin} {-ymin} cm\n'
ocrStream = ocrHeader + ocrStream + 'Q\n'
ocrContents = IndirectPdfDict(stream = ocrStream)
if not isinstance(pdfPage.Contents,PdfArray): pdfPage.Contents = [pdfPage.Contents]
pdfPage.Contents = [ocrContents] if debug else [ocrContents] + pdfPage.Contents
return pdf