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Implement automatic monochrome CCITT Group4 encoding via Pillow/libtiff

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James R. Barlow 2016-07-21 03:49:56 -07:00 committed by Johannes 'josch' Schauer
parent 0fe30a62d9
commit 95f84f97bc
1 changed files with 42 additions and 8 deletions
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48
src/img2pdf.py
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@ -58,7 +58,7 @@ PageOrientation = Enum('PageOrientation', 'portrait landscape')
Colorspace = Enum('Colorspace', 'RGB L 1 CMYK CMYK;I RGBA P other')
ImageFormat = Enum('ImageFormat', 'JPEG JPEG2000 other')
ImageFormat = Enum('ImageFormat', 'JPEG JPEG2000 CCITTGroup4 other')
PageMode = Enum('PageMode', 'none outlines thumbs')
@ -354,14 +354,15 @@ class pdfdoc(object):
imgwidthpdf, imgheightpdf, imgxpdf, imgypdf, pagewidth,
pageheight):
if self.with_pdfrw:
from pdfrw import PdfDict, PdfName
from pdfrw import PdfDict, PdfName, PdfObject
from pdfrw.py23_diffs import convert_load
else:
PdfDict = MyPdfDict
PdfName = MyPdfName
PdfObject = MyPdfObject
convert_load = my_convert_load
if color == Colorspace.L:
if color == Colorspace['1'] or color == Colorspace.L:
colorspace = PdfName.DeviceGray
elif color == Colorspace.RGB:
colorspace = PdfName.DeviceRGB
@ -372,11 +373,14 @@ class pdfdoc(object):
% color.name)
# either embed the whole jpeg or deflate the bitmap representation
logging.debug(imgformat)
if imgformat is ImageFormat.JPEG:
ofilter = [PdfName.DCTDecode]
elif imgformat is ImageFormat.JPEG2000:
ofilter = [PdfName.JPXDecode]
self.writer.version = "1.5" # jpeg2000 needs pdf 1.5
elif imgformat is ImageFormat.CCITTGroup4:
ofilter = [PdfName.CCITTFaxDecode]
else:
ofilter = [PdfName.FlateDecode]
@ -389,12 +393,23 @@ class pdfdoc(object):
image[PdfName.Height] = imgheightpx
image[PdfName.ColorSpace] = colorspace
# hardcoded as PIL doesn't provide bits for non-jpeg formats
if imgformat is ImageFormat.CCITTGroup4:
image[PdfName.BitsPerComponent] = 1
else:
image[PdfName.BitsPerComponent] = 8
if color == Colorspace['CMYK;I']:
# Inverts all four channels
image[PdfName.Decode] = [1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0]
if imgformat is ImageFormat.CCITTGroup4:
decodeparms = PdfDict()
decodeparms[PdfName.K] = -1
decodeparms[PdfName.BlackIs1] = PdfObject('true')
decodeparms[PdfName.Columns] = imgwidthpx
decodeparms[PdfName.Rows] = imgheightpx
image[PdfName.DecodeParms] = [decodeparms]
text = ("q\n%0.4f 0 0 %0.4f %0.4f %0.4f cm\n/Im0 Do\nQ" %
(imgwidthpdf, imgheightpdf, imgxpdf, imgypdf)).encode("ascii")
@ -648,11 +663,30 @@ def read_images(rawdata, colorspace, first_frame_only=False):
color, ndpi, imgwidthpx, imgheightpx = get_imgmetadata(
imgdata, imgformat, default_dpi, colorspace)
# because we do not support /CCITTFaxDecode
if color == Colorspace['1']:
logging.debug("Converting colorspace 1 to L")
newimg = imgdata.convert('L')
color = Colorspace.L
logging.debug("Converting monochrome to CCITT Group4")
# Convert the image to Group 4 in memory
newimgio = BytesIO()
imgdata.save(newimgio, format='TIFF', compression='group4')
# Open new image in memory
newimgio.seek(0)
newimg = Image.open(newimgio)
# Obtain tags
strip_offsets = newimg.tag_v2[273]
strip_bytes = newimg.tag_v2[279]
rows_per_strip = newimg.tag_v2[278]
newimgio.seek(strip_offsets[0])
ccittdata = newimgio.read(strip_bytes[0])
logging.debug("Extracted %i bytes from image" % len(ccittdata))
imgformat = ImageFormat.CCITTGroup4
result.append((color, ndpi, imgformat, ccittdata,
imgwidthpx, imgheightpx))
img_page_count += 1
continue
elif color in [Colorspace.RGB, Colorspace.L, Colorspace.CMYK,
Colorspace["CMYK;I"]]:
logging.debug("Colorspace is OK: %s", color)