From c27505486e2cb149aa87e69a7f71cf76ebf0732c Mon Sep 17 00:00:00 2001 From: "James R. Barlow" Date: Thu, 21 Jul 2016 14:42:48 -0700 Subject: [PATCH] Break out TIFF G4 transcoding into its own function --- src/img2pdf.py | 75 ++++++++++++++++++++++++++++++++++---------------- 1 file changed, 52 insertions(+), 23 deletions(-) diff --git a/src/img2pdf.py b/src/img2pdf.py index 3caaf75..4b222ad 100755 --- a/src/img2pdf.py +++ b/src/img2pdf.py @@ -609,6 +609,45 @@ def get_imgmetadata(imgdata, imgformat, default_dpi, colorspace, rawdata=None): return (color, ndpi, imgwidthpx, imgheightpx) +def transcode_monochrome(imgdata): + """Convert the open PIL.Image imgdata to compressed CCITT Group4 data""" + + from PIL import TiffImagePlugin + + logging.debug("Converting monochrome to CCITT Group4") + + # Convert the image to Group 4 in memory. If libtiff is not installed and + # Pillow is not compiled against it, .save() will raise an exception. + newimgio = BytesIO() + imgdata.save(newimgio, format='TIFF', compression='group4') + + # Open new image in memory + newimgio.seek(0) + newimg = Image.open(newimgio) + + # If Pillow is passed an invalid compression argument it will ignore it; + # make sure the image actually got compressed. + if newimg.info['compression'] != 'group4': + raise ValueError("Image not compressed as expected") + + # Read the TIFF tags to find the offset(s) of the compressed data strips. + strip_offsets = newimg.tag_v2[TiffImagePlugin.STRIPOFFSETS] + strip_bytes = newimg.tag_v2[TiffImagePlugin.STRIPBYTECOUNTS] + rows_per_strip = newimg.tag_v2[TiffImagePlugin.ROWSPERSTRIP] + + # PIL always seems to create a single strip even for very large TIFFs when + # it saves images, so assume we only have to read a single strip. + # A test ~10 GPixel image was still encoded as a single strip. Just to be + # safe check throw an error if there is more than one offset. + if len(strip_offsets) > 1: + raise NotImplementedError("Transcoding multiple strips not supported") + + newimgio.seek(strip_offsets[0]) + ccittdata = newimgio.read(strip_bytes[0]) + + return ccittdata + + def read_images(rawdata, colorspace, first_frame_only=False): im = BytesIO(rawdata) im.seek(0) @@ -663,30 +702,20 @@ def read_images(rawdata, colorspace, first_frame_only=False): color, ndpi, imgwidthpx, imgheightpx = get_imgmetadata( imgdata, imgformat, default_dpi, colorspace) + newimg = None if color == Colorspace['1']: - 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 + try: + ccittdata = transcode_monochrome(imgdata) + imgformat = ImageFormat.CCITTGroup4 + result.append((color, ndpi, imgformat, ccittdata, + imgwidthpx, imgheightpx)) + img_page_count += 1 + continue + except Exception as e: + logging.debug(e) + logging.debug("Converting colorspace 1 to L") + newimg = imgdata.convert('L') + color = Colorspace.L elif color in [Colorspace.RGB, Colorspace.L, Colorspace.CMYK, Colorspace["CMYK;I"]]: logging.debug("Colorspace is OK: %s", color)