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Add test cases for CCITT G4

This commit is contained in:
James R. Barlow 2016-07-21 16:33:26 -07:00 committed by Johannes 'josch' Schauer
parent c27505486e
commit eedf73e73e
3 changed files with 42 additions and 1 deletions

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@ -4,6 +4,8 @@ import os
import img2pdf
import zlib
from PIL import Image
from io import BytesIO
import struct
HERE = os.path.dirname(__file__)
@ -396,6 +398,28 @@ layout_test_cases = [
]
def tiff_header_for_ccitt(width, height, img_size, ccitt_group=4):
# Quick and dirty TIFF header builder from
# https://stackoverflow.com/questions/2641770/extracting-image-from-pdf-with-ccittfaxdecode-filter
tiff_header_struct = '<' + '2s' + 'h' + 'l' + 'h' + 'hhll' * 8 + 'h'
return struct.pack(
tiff_header_struct,
b'II', # Byte order indication: Little indian
42, # Version number (always 42)
8, # Offset to first IFD
8, # Number of tags in IFD
256, 4, 1, width, # ImageWidth, LONG, 1, width
257, 4, 1, height, # ImageLength, LONG, 1, lenght
258, 3, 1, 1, # BitsPerSample, SHORT, 1, 1
259, 3, 1, ccitt_group, # Compression, SHORT, 1, 4 = CCITT Group 4
262, 3, 1, 1, # Threshholding, SHORT, 1, 0 = WhiteIsZero
273, 4, 1, struct.calcsize(tiff_header_struct), # StripOffsets, LONG, 1, len of header
278, 4, 1, height, # RowsPerStrip, LONG, 1, lenght
279, 4, 1, img_size, # StripByteCounts, LONG, 1, size of image
0 # last IFD
)
def test_suite():
class TestImg2Pdf(unittest.TestCase):
pass
@ -485,7 +509,8 @@ def test_suite():
# test if the filter is valid:
self.assertIn(
imgprops.Filter, [[PdfName.DCTDecode], [PdfName.JPXDecode],
[PdfName.FlateDecode]])
[PdfName.FlateDecode],
[PdfName.CCITTFaxDecode]])
# test if the colorspace is valid
self.assertIn(
imgprops.ColorSpace, [PdfName.DeviceGray, PdfName.DeviceRGB,
@ -500,6 +525,22 @@ def test_suite():
self.assertEqual(
x.Root.Pages.Kids[0].Resources.XObject.Im0.stream,
convert_load(orig_imgdata))
elif imgprops.Filter == [PdfName.CCITTFaxDecode]:
tiff_header = tiff_header_for_ccitt(
int(imgprops.Width), int(imgprops.Height),
int(imgprops.Length), 4)
imgio = BytesIO()
imgio.write(tiff_header)
imgio.write(convert_store(
x.Root.Pages.Kids[0].Resources.XObject.Im0.stream))
imgio.seek(0)
im = Image.open(imgio)
self.assertEqual(im.tobytes(), orig_img.tobytes())
try:
im.close()
except AttributeError:
pass
elif imgprops.Filter == [PdfName.FlateDecode]:
# otherwise, the data is flate encoded and has to be equal to
# the pixel data of the input image

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