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22
README.md
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22
README.md
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# scanproc
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This is a tool to process high-resolution scans with as little user
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input as possible. It produces decently compressed PDF files with
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monochrome/color separation and more or less accurate text layers.
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## Requirements
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In addition to the Python modules listed in `requirements.txt`,
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scanproc requires [jbig2](https://github.com/agl/jbig2enc) to
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be installed in your `$PATH`.
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## Usage
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`scanproc.py [-h] [-l LANGS] [-d DPI] [--debug] output [imgs ...]`
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Usage is simple. You pass a list of
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[EasyOCR language codes](https://www.jaided.ai/easyocr/) to use
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with `-l` (default English only; pass multiple times for more than
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one language), the image resolution (required for filter kernel
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scaling and correct page size), followed by the output PDF file and
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the input image files.
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180
pdfutil.py
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180
pdfutil.py
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#!/usr/bin/env python3
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import struct
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import fitz
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import cv2 as cv
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class Dict:
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def __init__(self, values={}):
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self.d = {}
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self.d.update(values)
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def __bytes__(self):
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s = [b"<< "]
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for (x, y) in self.d.items():
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s.append(b"/" + x + b" " + y + b"\n")
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s.append(b">>\n")
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return b"".join(s)
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class Obj:
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def __init__(self, d={}, stream=None):
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if stream is not None:
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d[b"Length"] = str(len(stream)).encode()
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self.d = Dict(d)
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self.stream = stream
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self.idx = 0
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def __bytes__(self):
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s = [bytes(self.d)]
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if self.stream is not None:
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s.append(b"stream\n")
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s.append(self.stream)
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s.append(b"\nendstream\n")
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s.append(b"endobj\n")
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return b"".join(s)
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class Doc:
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def __init__(self):
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self.objs = []
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self.pages = []
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def add_object(self, o):
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o.idx = len(self.objs) + 1
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self.objs.append(o)
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return o
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def add_page(self, o):
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self.pages.append(o)
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return self.add_object(o)
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def __bytes__(self):
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a = []
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j = [0]
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offsets = []
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def add(x):
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a.append(x)
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j[0] += len(x) + 1
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add(b'%PDF-1.4')
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for o in self.objs:
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offsets.append(j[0])
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add(f"{o.idx} 0 obj".encode())
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add(bytes(o))
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xrefstart = j[0]
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a.append(b'xref')
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a.append(f'0 {len(offsets) + 1}'.encode())
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a.append(b'0000000000 65535 f ')
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for o in offsets:
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a.append(f"{o:010d} 00000 n ".encode())
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a.append(b'')
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a.append(b'trailer')
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a.append(f'<< /Size {len(offsets) + 1}\n/Root 1 0 R >>'.encode())
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a.append(b'startxref')
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a.append(str(xrefstart).encode())
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a.append(b'%EOF')
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return b'\n'.join(a)
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def ref(x):
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return f"{x} 0 R".encode()
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def mkpdf(symtab, pageblobs, colorimgs, texts, dpi):
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doc = Doc()
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doc.add_object(Obj({
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b'Type' : b'/Catalog',
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b'Outlines' : ref(2),
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b'Pages' : ref(3)
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}))
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doc.add_object(Obj({
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b'Type' : b'/Outlines',
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b'Count': b'0'
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}))
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pages = Obj({b'Type' : b'/Pages'})
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doc.add_object(pages)
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with open(symtab, "rb") as stab:
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symd = doc.add_object(Obj({}, stab.read()))
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page_objs = []
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for f in pageblobs:
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with open(f, "rb") as pf:
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blob = pf.read()
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(w, h, xres, yres) = struct.unpack(">IIII", blob[11:27])
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if xres == 0:
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xres = dpi
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if yres == 0:
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yres = dpi
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xobj = Obj({
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b'Type': b'/XObject',
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b'Subtype': b'/Image',
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b'Width': str(w).encode(),
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b'Height': str(h).encode(),
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b'ColorSpace': b'/DeviceGray',
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b'BitsPerComponent': b'1',
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b'Filter': b'/JBIG2Decode',
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b'DecodeParms': f' << /JBIG2Globals {symd.idx} 0 R >>'.encode()
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}, blob)
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xobj = doc.add_object(xobj)
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fw = float(w * 72) / xres
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fh = float(h * 72) / yres
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contents = Obj({}, f'q {fw:.1f} 0 0 {fh:.1f} 0 0 cm /Im1 Do Q'.encode())
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contents = doc.add_object(contents)
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resources = Obj({
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b'ProcSet': b'[/PDF /ImageB]',
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b'XObject': f'<< /Im1 {xobj.idx} 0 R >>'.encode()
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})
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resources = doc.add_object(resources)
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page = Obj({
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b'Type': b'/Page',
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b'Parent': b'3 0 R',
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b'MediaBox': f'[ 0 0 {fw:.1f} {fh:.1f} ]'.encode(),
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b'Contents': ref(contents.idx),
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b'Resources': ref(resources.idx)
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})
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doc.add_object(page)
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page_objs.append(page)
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pages.d.d[b'Count'] = str(len(page_objs)).encode()
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pages.d.d[b'Kids'] = b'[' + b' '.join([ref(x.idx) for x in page_objs]) + b']'
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pdf = fitz.open(stream=bytes(doc))
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for p, imgs in enumerate(colorimgs):
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for rect, img, mask in imgs:
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with open(mask, "rb") as mf:
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m = mf.read()
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pdf[p].insert_image(fitz.Rect(*[(c*72.0)/dpi for c in rect]), filename=img, mask=m)
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for p, txt in enumerate(texts):
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for box in txt:
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if len(box[1]):
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bbox = box[0]
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r = fitz.Rect(
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min((bbox[0][0]*72.0)/dpi, (bbox[3][0]*72.0)/dpi),
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min((bbox[0][1]*72.0)/dpi, (bbox[1][1]*72.0)/dpi),
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max((bbox[1][0]*72.0)/dpi, (bbox[2][0]*72.0)/dpi),
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max((bbox[2][1]*72.0)/dpi, (bbox[3][1]*72.0)/dpi)
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)
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fs = r.height
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w = fitz.get_text_length(box[1], fontsize=fs)
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pivot = fitz.Point(r.x0, r.y0)
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matrix = fitz.Matrix(r.width/w, 1.0)
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pdf[p].insert_text(fitz.Point(r.x0, r.y0+r.height*0.8),
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box[1], fontsize=fs,
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morph=(pivot, matrix),
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render_mode=3)
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return pdf.tobytes(garbage=4, clean=True, deflate=True)
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5
requirements.txt
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requirements.txt
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deskew
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easyocr
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entrypoint2
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pyMuPDF
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tqdm
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scanproc.py
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scanproc.py
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#!/usr/bin/env python3
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import easyocr
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import cv2 as cv
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import numpy as np
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import warnings
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from tqdm import tqdm
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from deskew import determine_skew
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from PIL import Image, ImageOps, ImageEnhance
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from entrypoint2 import entrypoint
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from pathlib import Path
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from tempfile import TemporaryDirectory
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from subprocess import run
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from pdfutil import mkpdf
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warnings.filterwarnings("ignore")
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def rotate(img, angle: float):
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(h, w) = img.shape[:2]
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center = (w//2, h//2)
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M = cv.getRotationMatrix2D(center, angle, 1.0)
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return cv.warpAffine(img, M, (w, h), flags=cv.INTER_CUBIC, borderMode=cv.BORDER_REPLICATE)
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def getRot(mask):
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(h, w) = mask.shape[:2]
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nw = min(w, 500)
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nh = int(h * (nw / w))
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sm = cv.resize(mask, (nw,nh))
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return determine_skew(sm)
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def getMono(img):
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gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)
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_, mono = cv.threshold(gray, 0, 255, cv.THRESH_BINARY + cv.THRESH_OTSU)
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kernel = np.ones((3,3),np.uint8)
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mono = cv.morphologyEx(mono, cv.MORPH_CLOSE, kernel)
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return mono
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def getColorMask(img, dpi):
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hsv = cv.cvtColor(img, cv.COLOR_BGR2HSV)
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lower_sat = np.array([0,40,10])
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upper_sat = np.array([255,255,255])
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mask = cv.inRange(hsv, lower_sat, upper_sat)
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ksiz = int(dpi*0.005)
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ksiz -= ksiz%2-1
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kernel = np.ones((ksiz,ksiz),np.uint8)
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mask = cv.erode(mask, kernel)
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mask = cv.dilate(mask, kernel, iterations = 5)
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br = int(dpi*.1)
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br -= br%2-1
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mask = cv.GaussianBlur(mask, (br,br), 0)
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_, mask = cv.threshold(mask, 0, 255, cv.THRESH_BINARY + cv.THRESH_OTSU)
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return mask
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def autoColorContrast(img, mono, dpi):
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ksiz = int(dpi*0.005)
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ksiz -= ksiz%2-1
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kernel = np.ones((ksiz,ksiz),np.uint8)
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mask = cv.bitwise_not(mono)
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mask = cv.dilate(mask, kernel, iterations = 5)
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pim = Image.fromarray(cv.cvtColor(img, cv.COLOR_BGR2RGB))
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pimask = Image.fromarray(mask)
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color = ImageOps.autocontrast(pim, (20, 30), mask=pimask, preserve_tone=True)
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color = cv.cvtColor(np.asarray(color), cv.COLOR_BGR2HLS)
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(H, L, S) = cv.split(color)
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L = L.astype("float32")
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L *= 1.3
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L = np.clip(L, 0, 255)
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L = L.astype("uint8")
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return cv.cvtColor(cv.merge((H, L, S)), cv.COLOR_HLS2RGB)
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def getColorSegments(img, mono, cmask):
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contours, hierarchy = cv.findContours(cmask, cv.RETR_LIST, cv.CHAIN_APPROX_SIMPLE)
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for c in contours:
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rect = cv.boundingRect(c)
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(x1, y1, x2, y2) = rect
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x2 += x1
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y2 += y1
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yield (x1, y1, x2, y2), img[y1:y2, x1:x2], cmask[y1:y2, x1:x2]
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def unsharpMask(image, kernel_size=(5, 5), sigma=1.0, amount=1.0, threshold=0):
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blurred = cv.GaussianBlur(image, kernel_size, sigma)
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sharpened = float(amount + 1) * image - float(amount) * blurred
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sharpened = np.maximum(sharpened, np.zeros(sharpened.shape))
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sharpened = np.minimum(sharpened, 255 * np.ones(sharpened.shape))
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sharpened = sharpened.round().astype(np.uint8)
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if threshold > 0:
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low_contrast_mask = np.absolute(image - blurred) < threshold
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np.copyto(sharpened, image, where=low_contrast_mask)
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return sharpened
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def processImage(img, reader, dpi):
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with tqdm(total=8, leave=False) as t:
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t.set_description("Reading image")
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im = cv.imread(img)
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t.update()
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t.set_description("Filter")
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mono = getMono(im)
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im = cv.cvtColor(im, cv.COLOR_RGB2Lab)
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(L, a, b) = cv.split(im)
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ksiz = int(dpi*0.015)
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ksiz -= ksiz%2-1
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L = unsharpMask(L, kernel_size=(ksiz,ksiz), amount=2)
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L = cv.bilateralFilter(L, -1, 12, dpi*0.018)
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im = cv.cvtColor(cv.merge((L, a, b)), cv.COLOR_Lab2RGB)
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im = autoColorContrast(im, mono, dpi)
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t.update()
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t.set_description("Detect skew")
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angle = getRot(im)
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t.update()
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t.set_description("Deskew")
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im = rotate(im, angle)
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mono = rotate(mono, angle)
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t.update()
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t.set_description("OCR")
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text = reader.readtext(mono)
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t.update()
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t.set_description("Color mask")
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cmask = getColorMask(im, dpi)
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t.update()
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t.set_description("Color segments")
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csegs = getColorSegments(im, mono, cmask)
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t.update()
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mono[cmask==255] = 255
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return mono, csegs, text
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@entrypoint
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def main(output, langs=["en"], dpi=600, *imgs):
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reader = easyocr.Reader(langs)
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with tqdm(total=3, leave=False) as t:
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with TemporaryDirectory() as tmp:
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tp = Path(tmp)
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files = []
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colorimgs = []
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texts = []
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t.set_description("Process pages")
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with tqdm(total=len(imgs), leave=False) as pt:
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for pagen, img in enumerate(imgs):
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pt.set_description(f"Process {img}")
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mono, csegs, text = processImage(img, reader, dpi)
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fn = str(tp / f"p{pagen}.tif")
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files.append(fn)
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cv.imwrite(fn, mono)
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pimgs = []
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for i, seg in enumerate(csegs):
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(r, simg, smask) = seg
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bp = tp / f"p{pagen}_{i}.jpg"
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mp = tp / f"p{pagen}_{i}_m.png"
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cv.imwrite(str(bp), simg, [
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cv.IMWRITE_JPEG_QUALITY, 90,
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cv.IMWRITE_JPEG_OPTIMIZE, 1,
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cv.IMWRITE_JPEG_PROGRESSIVE, 1])
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cv.imwrite(str(mp), smask, [
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cv.IMWRITE_PNG_BILEVEL, 1,
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cv.IMWRITE_PNG_COMPRESSION, 9])
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pimgs.append(((r), bp, mp))
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colorimgs.append(pimgs)
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texts.append(text)
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pt.update()
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t.update()
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t.set_description("JBIG2 compress")
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run(["jbig2", "-s", "-d", "-a", "-p", *files], capture_output=True, check=True, cwd=tp)
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symtab = tp / "output.sym"
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pageblobs = [tp / f"output.{p:04d}" for p in range(len(files))]
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t.update()
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t.set_description("Create PDF")
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with open(output, "wb") as outf:
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outf.write(mkpdf(symtab, pageblobs, colorimgs, texts, dpi))
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t.update()
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