(Tcl) PDF Signature with Background Image (Seal/Stamp/etc.)

See more PDF Signatures Examples

Demonstrates how to sign a PDF with an appearance that includes a background image, such as a seal, stamp, etc.

Note: This example requires Chilkat v9.5.0.85 or greater.

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load ./chilkat.dll

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

set pdf [new_CkPdf]

# Load a PDF to be signed.
# The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
set success [CkPdf_LoadFile $pdf "qa_data/pdf/hello.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    exit
}

set json [new_CkJsonObject]

# Put the signature on page 1, top left
CkJsonObject_UpdateInt $json "page" 1
CkJsonObject_UpdateString $json "appearance.y" "top"
CkJsonObject_UpdateString $json "appearance.x" "left"

# Use a font scale of 10.0
CkJsonObject_UpdateString $json "appearance.fontScale" "10.0"

# In this example, the appearance of the digital signature will contain three lines:
# 1) The signing certificate's common name
# 2) The current date/time
# 3) Some arbitrary text.
# The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
# The keyword "current_dt" is replaced with the current date/time.
# Any number of appearance text lines can be added.
CkJsonObject_UpdateString $json "appearance.text[0]" "Digitally signed by: cert_cn"
CkJsonObject_UpdateString $json "appearance.text[1]" "current_dt"
CkJsonObject_UpdateString $json "appearance.text[2]" "The crazy brown fox jumps over the lazy dog."

# Load a JPG image to be shown with 30% opacity in the background.
# (the image must be in the JPG format)
# The sample university.jpb is available at https://example-code.com/images/university.jpg

set jpgData [new_CkBinData]

set success [CkBinData_LoadFile $jpgData "qa_data/jpg/university.jpg"]
if {$success == 0} then {
    puts "Failed to load the JPG image."
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkBinData $jpgData
    exit
}

set success [CkPdf_SetSignatureJpeg $pdf $jpgData]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkBinData $jpgData
    exit
}

# Specify that we want to display the JPG image in the center with 30% opacity.
CkJsonObject_UpdateString $json "appearance.image" "custom-jpg"
CkJsonObject_UpdateString $json "appearance.imagePlacement" "center"
CkJsonObject_UpdateString $json "appearance.imageOpacity" "30"

# Load the signing certificate. (Use your own certificate.)
set cert [new_CkCert]

set success [CkCert_LoadPfxFile $cert "qa_data/pfx/myPdfSigningCert.pfx" "secret"]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkBinData $jpgData
    delete_CkCert $cert
    exit
}

# Tell the pdf object to use the certificate for signing.
set success [CkPdf_SetSigningCert $pdf $cert]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkBinData $jpgData
    delete_CkCert $cert
    exit
}

set success [CkPdf_SignPdf $pdf $json "qa_output/hello_signed.pdf"]
if {$success == 0} then {
    puts [CkPdf_lastErrorText $pdf]
    delete_CkPdf $pdf
    delete_CkJsonObject $json
    delete_CkBinData $jpgData
    delete_CkCert $cert
    exit
}

puts "The PDF has been successfully cryptographically signed."

# The appearance of the signature appears in Adobe Acrobat as shown below.
# The JPG is automatically scaled to the size of the signature based on the signature's font scale
# and number of text lines.


delete_CkPdf $pdf
delete_CkJsonObject $json
delete_CkBinData $jpgData
delete_CkCert $cert