Lua Requires Chilkat v11.7.0+

Get a PDF Field Value by its Label (Value to the Right)

See more PDF Text Extraction Examples

Demonstrates the "label" option, which captures the text that belongs to a caption such as "Invoice Number:" without needing coordinates. With labelValue "right", the value is the rest of the label's line. Label matching ignores case, extra spaces and a trailing colon. Lua

local chilkat = require("chilkat")

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

-- The invoice used in this example is available at invoice_labels.pdf

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

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

-- The invoice has lines such as "Invoice Number:   INV-2026-0412".
-- The label option restricts the "text" operation to the text belonging to the label.
json:update_string("label", "Invoice Number")

-- "right" means the value is the rest of the label's line.
-- (The default, "auto", uses the rest of the line if there is text there, otherwise the block below.)
json:update_string("labelValue", "right")

success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

-- The value is returned as the text.
print("Invoice Number: " .. jsonOut:string_of("text"))

-- The labelMatches array tells where the label was found and how it appeared in the PDF.
print("Found on page " .. jsonOut:int_of("labelMatches[0].page") .. " as \"" .. jsonOut:string_of("labelMatches[0].label") .. "\"")

-- Matching ignores case and the trailing colon, so these all work:
json:update_string("label", "CUSTOMER:")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("Customer: " .. jsonOut:string_of("text"))

json:update_string("label", "due date")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("Due Date: " .. jsonOut:string_of("text"))

-- The totals at the foot of the invoice are right-aligned labels with the amount beside them.
json:update_string("label", "Total Due")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

print("Total Due: " .. jsonOut:string_of("text"))

-- A label that is not found is not an error.  The text is empty, labelMatches is empty,
-- and the quality report has an issue with the code "labelNotFound".
json:update_string("label", "Tracking Number")
success = pdf:extract_text("text", json, jsonOut)
if not success then
    print(pdf.last_error_text)
    return
end

if jsonOut:size_of_array("labelMatches") == 0 then
    print("Tracking Number: (not found) " .. jsonOut:string_of("quality.pages[0].issues[0].code"))
end

-- Sample output:

-- Invoice Number: INV-2026-0412
-- Found on page 1 as "Invoice Number:"
-- Customer: Northwind Traders
-- Due Date: April 13, 2026
-- Total Due: $1,234.53
-- Tracking Number: (not found) labelNotFound