(Chilkat2-Python) PDF Signature Appearance Width and Height

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This example explains how the width and height of the signature appearance rectangle box is determined.

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

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import sys
import chilkat2

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

pdf = chilkat2.Pdf()

# Load a PDF to be signed.
# The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
success = pdf.LoadFile("qa_data/pdf/hello.pdf")
if (success == False):
    print(pdf.LastErrorText)
    sys.exit()

# Options for signing are specified in JSON.
json = chilkat2.JsonObject()

# In most cases, the signingCertificateV2 and signingTime attributes are required.
json.UpdateInt("signingCertificateV2",1)
json.UpdateInt("signingTime",1)

# Put the signature on page 1, top left
json.UpdateInt("page",1)
json.UpdateString("appearance.y","top")
json.UpdateString("appearance.x","left")

# Add some text.
json.UpdateString("appearance.text[0]","Digitally signed by: cert_cn")
json.UpdateString("appearance.text[1]","current_dt")

# Add a built-in SVG graphic to the right.
json.UpdateString("appearance.image","blue-check-mark")
json.UpdateString("appearance.imagePlacement","right")
json.UpdateString("appearance.imageOpacity","100")

# There are 4 ways the width and height of the signature rectangle can be specified.
# 1) The width and height (in points) are both explicitly specified.
#    User space coordinates use "points" where 72 points equals 1 inch.
#    For example (3 inches wide and 1 inch high)
#    The fontScale is automatically chose to fit.  In addition, if a graphic (JPG or built-in SVG) is included,
#    it is automatically scaled such that the text + graphic fit together in the specified rectangle.
#    Note: When both height and width are explicitly specified, the resultant signature appearance rectangle
#    will match one of the dimensions, but the other dimension will be equal or smaller.  This is because the text
#    must be proportionally scaled.
json.UpdateInt("appearance.width",72 * 3)
json.UpdateInt("appearance.height",72)

# The signature would have this appearance. In this case, the height is actually less than 1 inch because
# if Chilkat chose a fontScale to fill the height, the resulting text's width would be too long for the desired width. 


# 2) The width is explicitly specified, but we use the keyword "auto" for height.
#    In this case, the fontScale is chosen to achieve the desired width,
#    and the height will be whatever the result of the chosen font scale.
#    In this example, the width is 4 inches, and the height is "auto".
json.UpdateInt("appearance.width",72 * 4)
json.UpdateString("appearance.height","auto")

# The signature would have this appearance: 


# 3) The height is explicitly specified, but we use the keyword "auto" for width.
#    In this case, the fontScale is chosen to achieve the desired height,
#    and the width will be whatever the result of the chosen font scale.
#    In this example, the height is 1 inch (72 points) and the width is "auto".
json.UpdateString("appearance.width","auto")
json.UpdateInt("appearance.height",72)

# The signature would have this appearance.


# 4) Finally, we don't need to specify width/height at all.  Instead, we can choose a fontScale
#    and the dimensions of the PDF signature appearance's rectangle will be the result of using the
#    specified fontScale.

# jAppearance is a CkJsonObject
jAppearance = json.ObjectOf("appearance")
jAppearance.Delete("width")
jAppearance.Delete("height")

json.UpdateString("appearance.fontScale","10.0")

# With fontScale = "10.0"


# Load the signing certificate. (Use your own certificate.)
cert = chilkat2.Cert()
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password")
if (success == False):
    print(cert.LastErrorText)
    sys.exit()

# Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert)
if (success == False):
    print(pdf.LastErrorText)
    sys.exit()

success = pdf.SignPdf(json,"qa_output/hello_signed.pdf")
if (success == False):
    print(pdf.LastErrorText)
    sys.exit()

print("The PDF has been successfully cryptographically signed.")