(Ruby) 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.

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

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

pdf = Chilkat::CkPdf.new()

# 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() + "\n";
    exit
end

# Options for signing are specified in JSON.
json = Chilkat::CkJsonObject.new()

# 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 = Chilkat::CkCert.new()
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password")
if (success == false)
    print cert.lastErrorText() + "\n";
    exit
end

# Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert)
if (success == false)
    print pdf.lastErrorText() + "\n";
    exit
end

success = pdf.SignPdf(json,"qa_output/hello_signed.pdf")
if (success == false)
    print pdf.lastErrorText() + "\n";
    exit
end

print "The PDF has been successfully cryptographically signed." + "\n";