josch/img2pdf
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use resolution (DPI) from EXIF first, if not found or invalid, then use info from Pillow image

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Leo 2023-11-30 13:16:50 +08:00
parent 819b366bf5
commit 98493e6a9a
1 changed files with 21 additions and 2 deletions
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23
src/img2pdf.py
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@ -22,7 +22,7 @@ import sys
import os
import zlib
import argparse
from PIL import Image, TiffImagePlugin, GifImagePlugin, ImageCms
from PIL import Image, TiffImagePlugin, GifImagePlugin, ImageCms, ExifTags
if hasattr(GifImagePlugin, "LoadingStrategy"):
# Pillow 9.0.0 started emitting all frames but the first as RGB instead of
@ -1298,6 +1298,7 @@ class pdfdoc(object):
def get_imgmetadata(
imgdata, imgformat, default_dpi, colorspace, rawdata=None, rotreq=None
):
if imgformat == ImageFormat.JPEG2000 and rawdata is not None and imgdata is None:
# this codepath gets called if the PIL installation is not able to
# handle JPEG2000 files
@ -1311,7 +1312,25 @@ def get_imgmetadata(
else:
imgwidthpx, imgheightpx = imgdata.size
ndpi = imgdata.info.get("dpi")
ndpi = None
# For JPEG images with both EXIF tags and JFIF tags, Pillow seems reading image resolution from JFIF.
# However, "Preview" on Mac and "Photos" on Windows read the resolution from EXIF.
# We try to read the value from EXIF first
exif = imgdata.getexif()
if exif:
exif_res_unit = exif.get(ExifTags.Base.ResolutionUnit)
exif_x_res = exif.get(ExifTags.Base.XResolution)
exif_y_res = exif.get(ExifTags.Base.YResolution)
if exif_x_res and exif_y_res:
if (exif_res_unit == 3): # cm
ndpi = (exif_x_res * 2.54, exif_y_res * 2.54)
else:
ndpi = (exif_x_res, exif_y_res)
# if no DPI from EXIF, get it from `info`
if ndpi is None:
ndpi = imgdata.info.get("dpi")
if ndpi is None:
# the PNG plugin of PIL adds the undocumented "aspect" field instead of
# the "dpi" field if the PNG pHYs chunk unit is not set to meters