我的目標是擁有一個 Python 腳本，它將獲取 PDF、提取其影像、壓縮/調整它們的大小，然后將這些新資料推送到 PDF，這將產生一個新的、更小的 PDF。
到目前為止，除了用正確的對應物替換影像資料之外，我已經完成了所有作業。我找到了影像資料所在的正確位置（在“stream”和“streamend”標簽之間）。
這是我的代碼（更新）：
def crunchPdfImages(file_to_crunch, max_width=1200, max_height=628):
page_ratio = max_width / max_height
working_folder = os.path.dirname(file_to_crunch)
working_dir = os.path.join(working_folder, "temp_working_dir")
if not (os.path.exists(working_dir)): os.mkdir(working_dir)
# Get all the image...
extractPDFImages(file_to_crunch, working_dir)
# Compress all the images... (no resize)
all_image_list = [entry.path for entry in os.scandir(working_dir) if isImage(entry.path)]
for an_image in all_image_list:
img_picture = Image.open(an_image).convert("RGB")
img_picture.save(an_image, "JPEG", optimize=True)
# Uncompress the PDF
pdf_folder = os.path.join(working_dir, "pdf_uncompressed")
if not (os.path.exists(pdf_folder)): os.mkdir(pdf_folder)
pdf_datain_file = os.path.join(pdf_folder, "uncompressed_pdf.pdf")
pdf_dataout_file = os.path.join(pdf_folder, "new_images_pdf.pdf")
pypdftk.uncompress('"' file_to_crunch '"', pdf_datain_file)
# Now get to work...
# The PDF is comprised of objects, some of which are lablled as images.
# Each image has the line "/Subtype /Image" before the "stream" which is then ended by "endstream" then "endobj".
# In between the stream and endstream is the encoded image data... hopefully I can replace this in the same order that
# the images were taken out.
picture_replace_count = 0
pdf_openfile_in = open(pdf_datain_file, "rb")
pdf_openfile_out = open(pdf_dataout_file, "wb")
pdf_file_lines = pdf_openfile_in.readlines()
looking_for_next_stream = False
found_stream_and_removing = False
updating_xref_stage = 0
skip_a_line = False
for line in pdf_file_lines:
new_line_addition = "" # For adding to byte count, resetting to null here just in case
current_line_val = line.decode("Latin-1").strip()
if (looking_for_next_stream):
# Last image tag has been found but not dealt with, so find the stream then
if (current_line_val[:8] == "/Length "):
# Update the length
skip_a_line = True
new_img_size = str(os.path.getsize(all_image_list[picture_replace_count]))
new_line = r"/Length " new_img_size "\n"
pdf_openfile_out.write(new_line.encode("latin-1")) # add new line
if (current_line_val == "stream"):
print("Stream start found... skipping stream information")
looking_for_next_stream = False # it's been found
found_stream_and_removing = True # time to delete
new_line_addition = "stream\n".encode("latin-1")
pdf_openfile_out.write(new_line_addition) # add the line in or it will be skipped
elif (found_stream_and_removing):
if (current_line_val == "endstream"):
print("Stream end found")
found_stream_and_removing = False # Passed through all image data line
# Now, add in the new image data and continue on.
print("Adding new image data...")
#new_image_file = open(all_image_list[picture_replace_count], "rb")
img = Image.open(all_image_list[picture_replace_count], mode='r')
img_byte_arr = io.BytesIO()
img.save(img_byte_arr, format='JPEG')
img_byte_arr = img_byte_arr.getvalue()
pdf_openfile_out.write(img_byte_arr)
new_line_addition = img_byte_arr
"""
for imgline in new_image_file.readlines():
#pdf_openfile_out.write(imgline.encode("Latin-1"))
#pdf_openfile_out.write(imgline)
pass
#pdf_openfile_out.write("[IMAGEADD]".encode("latin-1")) # add new line
"""
#new_image_file.close()
picture_replace_count = 1
print("New image added.")
pdf_openfile_out.write("\n".encode("latin-1")) # add new line
if (picture_replace_count >= len(all_image_list)):
updating_xref_stage = 1 # All images replaced, now edit the xref.
elif (current_line_val == r"/Subtype /Image"):
print("Found an image place, number " str(picture_replace_count))
print("Looking for stream start...")
looking_for_next_stream = True
# Find next
if not (found_stream_and_removing) and not (skip_a_line) and not (updating_xref_stage == 4):
pdf_openfile_out.write(line)
skip_a_line = False
pdf_openfile_in.close()
pdf_openfile_out.close()
print("Rebuilding xref table (post newfile creation)")
rebuildXrefTable(pdf_dataout_file)
為了重建外部參照表（根據此處的評論），我運行以下函式。我確實嘗試在前一個函式中執行此操作，但資料最終以不同的大小輸出。我還沒有弄清楚如何將照片日期準確地推送到 PDF 流中。
def rebuildXrefTable(pdf_file_in, pdf_file_out=None):
# Updating the xref table:
# * Assumes uncompressed PDF file
# To do this I need the number of bytes that precede and object (this is used as a reference).
# So, each line I will need to count the byte number and tally up
# When an object is found, the byte_count will be added to the reference list and then used to create the xref table
# Also need to update the "startxref" at the bottom (similar principle).
if (pdf_file_out == None): pdf_file_out = os.path.join(os.path.dirname(pdf_file_in), "rebuilt_xref_pdf.pdf")
print("Updating xref table of: " os.path.basename(pdf_file_in))
byte_count = 0
xref_start = 0
object_location_reference = []
updating_xref_stage = 1
pdf_openfile_in = open(pdf_file_in, "rb")
pdf_openfile_out = open(pdf_file_out, "wb")
pdf_file_lines = pdf_openfile_in.readlines()
for line in pdf_file_lines:
current_line_val = line.decode("Latin-1").strip()
if (" obj" in current_line_val):
# Check if the place is an object loc, store byte reference and object index
obj_ref_index = current_line_val.split(" ")[0]
print("Found new object (index, location): (" str(obj_ref_index) ", " str(byte_count) ")")
object_location_reference.append((int(obj_ref_index), byte_count))
elif ("startxref" in current_line_val):
# This is the last thing to edit (right at the bottom, update the xref start location and then add the file end.
print("Updating the xref start value with new data...")
new_line = "startxref\n" str(xref_start) "\n" r"%%EOF"
pdf_openfile_out.write(new_line.encode("latin-1"))
break
elif ("xref" in current_line_val):
print("Recording the new xref byte location")
preceeding_str = current_line_val.split("xref")[0]
preceeding_count = len(preceeding_str.encode("latin-1"))
xref_start = byte_count preceeding_count # used at the end
updating_xref_stage = 2
elif (updating_xref_stage == 2 or updating_xref_stage == 3):
# This stage simply skips the first 2 xref data lines (and prints it o the new file as is)
updating_xref_stage = 1
elif (updating_xref_stage == 4):
print("Creating new xref object byte location table...")
object_location_reference.sort() # Sort the collected xref locations by their object index.
# Now add the new xref data information
for xref_loc in object_location_reference:
new_val = str(xref_loc[1]).zfill(10) # Pad the number out
new_val = new_val " 00000 n \n"
pdf_openfile_out.write(new_val.encode("latin-1"))
updating_xref_stage = 5
elif (updating_xref_stage == 5):
# Stage 5 doesn't record the read in lines into new file
if ("trailer" in current_line_val): updating_xref_stage = 5
# Write to file
if not (updating_xref_stage == 5):
pdf_openfile_out.write(line)
byte_count = len(line)
pdf_openfile_in.close()
pdf_openfile_out.close()
外部參照表是準確的并指向正確的位元組位置，我還確保它的順序正確（使用物件索引號，而不是它在檔案中出現的順序——這與原始 PDF 檔案匹配）。
如果我不嘗試替換任何東西，只是將資料吐出到新的 PDF 檔案中，它就可以作業，我可以打開新檔案。但是，當插入替換 JPG 資料時，PDF 無法打開，因為它已損壞。
我不知道如何將正確的資料從壓縮影像推送到 PDF 檔案。
我也嘗試過像這樣簡單地推送 JPG 資料：
image = open(all_image_list[picture_replace_count], 'rb')
pdf_openfile_out.write(image.read())
image.close()
使用：Python 3.8
uj5u.com熱心網友回復：
感謝這里的評論，我已經解決了這個問題。必須重建外部參照表，并將 JPG 資料作為一個整體放入。這是作業代碼：
def crunchPdfImages(file_to_crunch):
working_folder = os.path.dirname(file_to_crunch)
working_dir = os.path.join(working_folder, "temp_working_dir")
if not (os.path.exists(working_dir)): os.mkdir(working_dir)
# Get all the image...
extractPDFImages(file_to_crunch, working_dir)
# Compress all the images... (no resize, just optimise)
all_image_list = [entry.path for entry in os.scandir(working_dir) if isImage(entry.path)]
if (len(all_image_list) > 0):
for an_image in all_image_list:
img_picture = Image.open(an_image).convert("RGB")
img_picture.save(an_image, "JPEG", optimize=True)
else:
print("No images found in PDF...")
# Uncompress the PDF
pdf_folder = os.path.join(working_dir, "pdf_uncompressed")
if not (os.path.exists(pdf_folder)): os.mkdir(pdf_folder)
pdf_datain_file = os.path.join(pdf_folder, "uncompressed_pdf.pdf")
pdf_dataout_file = os.path.join(pdf_folder, "new_images_pdf.pdf")
print("Uncompressing PDF...")
pypdftk.uncompress('"' file_to_crunch '"', '"' pdf_datain_file '"')
# Now get to work...
# The PDF is comprised of objects, some of which are lablled as images.
# Each image has the line "/Subtype /Image" before the "stream" which is then ended by "endstream" then "endobj".
# In between the stream and endstream is the encoded image data... hopefully I can replace this in the same order that
# the images were taken out.
picture_replace_count = 0
pdf_openfile_in = open(pdf_datain_file, "rb")
pdf_openfile_out = open(pdf_dataout_file, "wb")
pdf_file_lines = pdf_openfile_in.readlines()
looking_for_next_stream = False
found_stream_and_removing = False
skip_a_line = False
for line in pdf_file_lines:
new_line_addition = "" # For adding to byte count, resetting to null here just in case
current_line_val = line.decode("Latin-1").strip()
if (looking_for_next_stream):
# Last image tag has been found but not dealt with, so find the stream then
if (current_line_val[:8] == "/Length "):
# Update the length
skip_a_line = True
new_img_size = str(os.path.getsize(all_image_list[picture_replace_count]))
new_line = r"/Length " new_img_size "\n"
pdf_openfile_out.write(new_line.encode("latin-1")) # add new line
if (current_line_val == "stream"):
print("Stream start found... skipping stream information")
looking_for_next_stream = False # it's been found
found_stream_and_removing = True # time to delete
new_line_addition = "stream\n".encode("latin-1")
pdf_openfile_out.write(new_line_addition) # add the line in or it will be skipped
elif (found_stream_and_removing):
if (current_line_val == "endstream"):
print("Stream end found")
found_stream_and_removing = False # Passed through all image data line
# Now, add in the new image data and continue on.
print("Adding new image data...")
image = open(all_image_list[picture_replace_count], 'rb')
pdf_openfile_out.write(image.read())
image.close()
picture_replace_count = 1
pdf_openfile_out.write("\n".encode("latin-1")) # add new line
elif (current_line_val == r"/Subtype /Image"):
print("Found an image place, number " str(picture_replace_count))
print("Looking for stream start...")
looking_for_next_stream = True
# Find next
if not (found_stream_and_removing) and not (skip_a_line):
pdf_openfile_out.write(line)
skip_a_line = False
pdf_openfile_in.close()
pdf_openfile_out.close()
print("Rebuilding xref table (post newfile creation)")
rebuildXrefTable(pdf_dataout_file)
def rebuildXrefTable(pdf_file_in, pdf_file_out=None):
# Updating the xref table:
# * Assumes uncompressed PDF file
# To do this I need the number of bytes that precede and object (this is used as a reference).
# So, each line I will need to count the byte number and tally up
# When an object is found, the byte_count will be added to the reference list and then used to create the xref table
# Also need to update the "startxref" at the bottom (similar principle).
if (pdf_file_out == None): pdf_file_out = os.path.join(os.path.dirname(pdf_file_in), "rebuilt_xref_pdf.pdf")
print("Updating xref table of: " os.path.basename(pdf_file_in))
byte_count = 0
xref_start = 0
object_location_reference = []
updating_xref_stage = 1
pdf_openfile_in = open(pdf_file_in, "rb")
pdf_openfile_out = open(pdf_file_out, "wb")
pdf_file_lines = pdf_openfile_in.readlines()
for line in pdf_file_lines:
current_line_val = line.decode("Latin-1").strip()
if (" obj" in current_line_val):
# Check if the place is an object loc, store byte reference and object index
obj_ref_index = current_line_val.split(" ")[0]
print("Found new object (index, location): (" str(obj_ref_index) ", " str(byte_count) ")")
object_location_reference.append((int(obj_ref_index), byte_count))
elif ("startxref" in current_line_val):
# This is the last thing to edit (right at the bottom, update the xref start location and then add the file end.
print("Updating the xref start value with new data...")
new_line = "startxref\n" str(xref_start) "\n" r"%%EOF"
pdf_openfile_out.write(new_line.encode("latin-1"))
break
elif ("xref" in current_line_val):
print("Recording the new xref byte location")
preceeding_str = current_line_val.split("xref")[0]
preceeding_count = len(preceeding_str.encode("latin-1"))
xref_start = byte_count preceeding_count # used at the end
updating_xref_stage = 2
elif (updating_xref_stage == 2 or updating_xref_stage == 3):
# This stage simply skips the first 2 xref data lines (and prints it o the new file as is)
updating_xref_stage = 1
elif (updating_xref_stage == 4):
print("Creating new xref object byte location table...")
object_location_reference.sort() # Sort the collected xref locations by their object index.
# Now add the new xref data information
for xref_loc in object_location_reference:
new_val = str(xref_loc[1]).zfill(10) # Pad the number out
new_val = new_val " 00000 n \n"
pdf_openfile_out.write(new_val.encode("latin-1"))
updating_xref_stage = 5
elif (updating_xref_stage == 5):
# Stage 5 doesn't record the read in lines into new file, step 6 will.
if ("trailer" in current_line_val): updating_xref_stage = 6
# Write to file
if not (updating_xref_stage == 5):
pdf_openfile_out.write(line)
byte_count = len(line)
pdf_openfile_in.close()
pdf_openfile_out.close()
# To use the PDF compression:
crunchPdfImages(r"C:\Users\Person\Desktop\Test Folder\Pdf File.pdf")
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