OCRmyPDF/tests/test_rotation.py

# © 2018 James R. Barlow: github.com/jbarlow83
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.


import operator
from io import BytesIO
from math import cos, pi, sin
from os import fspath

import img2pdf
import pikepdf
import pytest
from PIL import Image, ImageChops
from reportlab.pdfgen.canvas import Canvas

from ocrmypdf._exec import ghostscript
from ocrmypdf._plugin_manager import get_plugin_manager
from ocrmypdf.helpers import Resolution
from ocrmypdf.pdfinfo import PdfInfo

from .conftest import check_ocrmypdf, run_ocrmypdf

# pylintx: disable=unused-variable


RENDERERS = ['hocr', 'sandwich']


def compare_images_monochrome(
    outdir, reference_pdf, reference_pageno, test_pdf, test_pageno
):
    reference_png = outdir / f'{reference_pdf.name}.ref{reference_pageno:04d}.png'
    test_png = outdir / f'{test_pdf.name}.test{test_pageno:04d}.png'

    def rasterize(pdf, pageno, png):
        if png.exists():
            print(png)
            return
        ghostscript.rasterize_pdf(
            pdf,
            png,
            raster_device='pngmono',
            raster_dpi=Resolution(100, 100),
            pageno=pageno,
            rotation=0,
        )

    rasterize(reference_pdf, reference_pageno, reference_png)
    rasterize(test_pdf, test_pageno, test_png)

    with Image.open(reference_png) as reference_im, Image.open(test_png) as test_im:
        assert reference_im.mode == test_im.mode == '1'
        difference = ImageChops.logical_xor(reference_im, test_im)
        assert difference.mode == '1'

        histogram = difference.histogram()
        assert (
            len(histogram) == 256
        ), "Expected Pillow to convert to grayscale for histogram"

        # All entries other than first and last will be 0
        count_same = histogram[0]
        count_different = histogram[-1]
        total = count_same + count_different

        return count_same / (total)


def test_monochrome_comparison(resources, outdir):
    # Self test: check that an incorrect rotated image has poor
    # comparison with reference
    cmp = compare_images_monochrome(
        outdir,
        reference_pdf=resources / 'cardinal.pdf',
        reference_pageno=1,  # north facing page
        test_pdf=resources / 'cardinal.pdf',
        test_pageno=3,  # south facing page
    )
    assert cmp < 0.90
    cmp = compare_images_monochrome(
        outdir,
        reference_pdf=resources / 'cardinal.pdf',
        reference_pageno=2,
        test_pdf=resources / 'cardinal.pdf',
        test_pageno=2,
    )
    assert cmp > 0.95


@pytest.mark.slow
@pytest.mark.parametrize('renderer', RENDERERS)
def test_autorotate(renderer, resources, outdir):
    # cardinal.pdf contains four copies of an image rotated in each cardinal
    # direction - these ones are "burned in" not tagged with /Rotate
    check_ocrmypdf(
        resources / 'cardinal.pdf',
        outdir / 'out.pdf',
        '-r',
        '-v',
        '1',
        '--pdf-renderer',
        renderer,
        '--plugin',
        'tests/plugins/tesseract_cache.py',
    )
    for n in range(1, 4 + 1):
        cmp = compare_images_monochrome(
            outdir,
            reference_pdf=resources / 'cardinal.pdf',
            reference_pageno=1,
            test_pdf=outdir / 'out.pdf',
            test_pageno=n,
        )
        assert cmp > 0.95


@pytest.mark.parametrize(
    'threshold, op, comparison_threshold',
    [
        ('1', operator.ge, 0.95),  # Low thresh -> always rotate -> high score
        ('99', operator.le, 0.90),  # High thres -> never rotate -> low score
    ],
)
def test_autorotate_threshold(threshold, op, comparison_threshold, resources, outdir):
    check_ocrmypdf(
        resources / 'cardinal.pdf',
        outdir / 'out.pdf',
        '--rotate-pages-threshold',
        threshold,
        '-r',
        # '-v',
        # '1',
        '--plugin',
        'tests/plugins/tesseract_cache.py',
    )

    cmp = compare_images_monochrome(  # pylint: disable=unused-variable
        outdir,
        reference_pdf=resources / 'cardinal.pdf',
        reference_pageno=1,
        test_pdf=outdir / 'out.pdf',
        test_pageno=3,
    )

    assert op(cmp, comparison_threshold)


def test_rotated_skew_timeout(resources, outpdf):
    """This document contains an image that is rotated 90 into place with a
    /Rotate tag and intentionally skewed by altering the transformation matrix.

    This tests for a bug where the combination of preprocessing and a tesseract
    timeout produced a page whose dimensions did not match the original's.
    """

    input_file = resources / 'rotated_skew.pdf'
    in_pageinfo = PdfInfo(input_file)[0]

    assert (
        in_pageinfo.height_pixels < in_pageinfo.width_pixels
    ), "Expected the input page to be landscape"
    assert in_pageinfo.rotation == 90, "Expected a rotated page"

    out = check_ocrmypdf(
        input_file,
        outpdf,
        '--pdf-renderer',
        'hocr',
        '--deskew',
        '--tesseract-timeout',
        '0',
    )

    out_pageinfo = PdfInfo(out)[0]
    w, h = out_pageinfo.width_pixels, out_pageinfo.height_pixels

    assert h > w, "Expected the output page to be portrait"

    assert out_pageinfo.rotation == 0, "Expected no page rotation for output"

    assert (
        in_pageinfo.width_pixels == h and in_pageinfo.height_pixels == w
    ), "Expected page rotation to be baked in"


@pytest.mark.xfail(reason="tesseract timeout blocks tesseract based deskew")
def test_rotate_deskew_timeout(resources, outdir):
    check_ocrmypdf(
        resources / 'rotated_skew.pdf',
        outdir / 'deskewed.pdf',
        '--rotate-pages',
        '--rotate-pages-threshold',
        '0',
        '--deskew',
        '--tesseract-timeout',
        '0',
        '--pdf-renderer',
        'sandwich',
    )

    cmp = compare_images_monochrome(
        outdir,
        reference_pdf=resources / 'ccitt.pdf',
        reference_pageno=1,
        test_pdf=outdir / 'deskewed.pdf',
        test_pageno=1,
    )

    # Confirm that the page still got deskewed
    assert cmp > 0.95


@pytest.mark.slow
@pytest.mark.parametrize('page_angle', (0, 90, 180, 270))
@pytest.mark.parametrize('image_angle', (0, 90, 180, 270))
def test_rotate_page_level(image_angle, page_angle, resources, outdir):
    def make_rotate_test(prefix, image_angle, page_angle):
        memimg = BytesIO()
        with Image.open(fspath(resources / 'typewriter.png')) as im:
            if image_angle != 0:
                ccw_angle = -image_angle % 360
                im = im.transpose(getattr(Image, f'ROTATE_{ccw_angle}'))
            im.save(memimg, format='PNG')
        memimg.seek(0)
        mempdf = BytesIO()
        img2pdf.convert(
            memimg.read(),
            layout_fun=img2pdf.get_fixed_dpi_layout_fun((200, 200)),
            outputstream=mempdf,
        )
        mempdf.seek(0)
        pike = pikepdf.open(mempdf)
        pike.pages[0].Rotate = page_angle
        target = outdir / f'{prefix}_{image_angle}_{page_angle}.pdf'
        pike.save(target)
        return target

    reference = make_rotate_test('ref', 0, 0)
    test = make_rotate_test('test', image_angle, page_angle)
    out = test.with_suffix('.out.pdf')

    p = run_ocrmypdf(
        test,
        out,
        '-O0',
        '--rotate-pages',
        '--rotate-pages-threshold',
        '0.001',
        text=False,
    )
    err = p.stderr.decode('utf-8', errors='replace')
    assert p.returncode == 0, err

    assert compare_images_monochrome(outdir, reference, 1, out, 1) > 0.2


def test_rasterize_rotates(resources, tmp_path):
    pm = get_plugin_manager([])

    img = tmp_path / 'img90.png'
    pm.hook.rasterize_pdf_page(
        input_file=resources / 'graph.pdf',
        output_file=img,
        raster_device='pngmono',
        raster_dpi=Resolution(20, 20),
        page_dpi=Resolution(20, 20),
        pageno=1,
        rotation=90,
        filter_vector=False,
    )
    assert Image.open(img).size == (123, 151), "Image not rotated"

    img = tmp_path / 'img180.png'
    pm.hook.rasterize_pdf_page(
        input_file=resources / 'graph.pdf',
        output_file=img,
        raster_device='pngmono',
        raster_dpi=Resolution(20, 20),
        page_dpi=Resolution(20, 20),
        pageno=1,
        rotation=180,
        filter_vector=False,
    )
    assert Image.open(img).size == (151, 123), "Image not rotated"


def test_simulated_scan(outdir):
    canvas = Canvas(
        fspath(outdir / 'fakescan.pdf'),
        pagesize=(209.8, 297.6),
    )

    page_vars = [(2, 36, 250), (91, 170, 240), (179, 190, 36), (271, 36, 36)]

    for n, page_var in enumerate(page_vars):
        text = canvas.beginText()
        text.setFont('Helvetica', 20)

        angle, x, y = page_var
        cos_a, sin_a = cos(angle / 180.0 * pi), sin(angle / 180.0 * pi)

        text.setTextTransform(cos_a, -sin_a, sin_a, cos_a, x, y)
        text.textOut(f'Page {n + 1}')
        canvas.drawText(text)
        canvas.showPage()
    canvas.save()

    check_ocrmypdf(
        outdir / 'fakescan.pdf',
        outdir / 'out.pdf',
        '--force-ocr',
        '--deskew',
        '--rotate-pages',
        '--plugin',
        'tests/plugins/tesseract_debug_rotate.py',
    )

    with pikepdf.open(outdir / 'out.pdf') as pdf:
        assert (
            pdf.pages[1].MediaBox[2] > pdf.pages[1].MediaBox[3]
        ), "Wrong orientation: not landscape"
        assert (
            pdf.pages[3].MediaBox[2] > pdf.pages[3].MediaBox[3]
        ), "Wrong orientation: Not landscape"

        assert (
            pdf.pages[0].MediaBox[2] < pdf.pages[0].MediaBox[3]
        ), "Wrong orientation: Not portrait"
        assert (
            pdf.pages[2].MediaBox[2] < pdf.pages[2].MediaBox[3]
        ), "Wrong orientation: Not portrait"