Lua Requires Chilkat v11.7.0+

Extract Text from a Two-Column PDF

See more PDF Text Extraction Examples

Demonstrates how multi-column pages are read. By default the columns are detected and each column is read top to bottom before the next ("columns": "auto"); "columns": "none" reads the full page width line by line, which interleaves the columns. The quality report tells how many columns were found. Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

-- The two-column PDF used in this example is available at two_column_article.pdf

local pdf = chilkat.Pdf.new()
local success = pdf:load_file("qa_data/pdf/two_column_article.pdf")
if not success then
    print(pdf.last_error_text)
    return
end

local json = chilkat.JsonObject.new()
local jsonOut = chilkat.JsonObject.new()

-- With the default options the columns are detected, and the text of the left column
-- comes before the text of the right column.
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("Columns detected: " .. jsonOut:int_of("quality.pages[0].columns"))
print("Reading order: " .. jsonOut:string_of("quality.pages[0].readingOrderSource"))
print(jsonOut:string_of("text"))

-- "none" switches column detection off: the page is read across its full width, line by line,
-- so each output line holds a line of the left column followed by a line of the right column.
-- This is rarely wanted, but it shows what the detection does.
json:update_string("columns", "none")
json:update_string("layout", "lines")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("---- columns: none ----")
print(jsonOut:string_of("text"))

-- Sample output (abbreviated):

-- Columns detected: 2
-- Reading order: visual
-- The Harbor Lighthouse, Season Two
--
-- The harbor lighthouse was built in 1874 to mark the entrance to the inner channel. It operated continuously until 1968, ...
--
-- The restoration society took ownership in 2021 with three goals: ...
-- ...
-- The lantern room frame was stripped, primed and repainted in the original dark green. ...
-- ...
-- ---- columns: none ----
-- The Harbor Lighthouse, Season Two
-- The harbor lighthouse was built in 1874 to The lantern room frame was stripped, primed
-- mark the entrance to the inner channel. It and repainted in the original dark green. New
-- ...