Lua Requires Chilkat v11.7.0+

Get Every Occurrence of a Label in a PDF

See more PDF Text Extraction Examples

Demonstrates the "labelOccurrence" option. When the same label appears more than once (for example "Total:" on each of several receipts), "first" (the default) uses the first occurrence, "all" returns every occurrence with its page, and a number selects one occurrence. Lua

local chilkat = require("chilkat")

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

-- The PDF used in this example (three receipts, one per page) is available at three_receipts.pdf

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

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

-- Each of the three pages is a receipt with a "Total:" line.
json:update_string("label", "Total")
json:update_string("labelValue", "right")

-- By default only the first occurrence (in reading order) is used.
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("First total: " .. jsonOut:string_of("text"))

-- labelOccurrence "all" returns every occurrence.  The "text" member holds the values joined
-- by line breaks, and labelMatches has one entry per occurrence with its page.
json:update_string("labelOccurrence", "all")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

local i = 0
local count_i = jsonOut:size_of_array("labelMatches")
while i < count_i do
    jsonOut.i = i
    print("Page " .. jsonOut:int_of("labelMatches[i].page") .. " total: " .. jsonOut:string_of("labelMatches[i].text"))
    i = i + 1
end

-- A number selects one occurrence: 2 is the second.
json:update_int("labelOccurrence", 2)
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("Second total: " .. jsonOut:string_of("text"))

-- The occurrences are counted over the selected pages, so combining "pages" with the label
-- is another way to pick one receipt:
json:update_string("labelOccurrence", "first")
json:update_string("pages", "3")
json:update_string("label", "Receipt No.")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("Receipt number on page 3: " .. jsonOut:string_of("text"))

-- Sample output:

-- First total: $19.86
-- Page 1 total: $19.86
-- Page 2 total: $17.34
-- Page 3 total: $23.62
-- Second total: $17.34
-- Receipt number on page 3: 1003