(Android™) PDF Signature Appearance Width and Height

See more PDF Signatures Examples

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.

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// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

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

    CkPdf pdf = new CkPdf();

    // Load a PDF to be signed.
    // The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    boolean success = pdf.LoadFile("qa_data/pdf/hello.pdf");
    if (success == false) {
        Log.i(TAG, pdf.lastErrorText());
        return;
        }

    // Options for signing are specified in JSON.
    CkJsonObject json = new CkJsonObject();

    // 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.

    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.)
    CkCert cert = new CkCert();
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password");
    if (success == false) {
        Log.i(TAG, cert.lastErrorText());
        return;
        }

    // Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert);
    if (success == false) {
        Log.i(TAG, pdf.lastErrorText());
        return;
        }

    success = pdf.SignPdf(json,"qa_output/hello_signed.pdf");
    if (success == false) {
        Log.i(TAG, pdf.lastErrorText());
        return;
        }

    Log.i(TAG, "The PDF has been successfully cryptographically signed.");

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}