C
C
PDF Signature Page Location
See more PDF Signatures Examples
This example demonstrates how to specify the location of a PDF signature on a page.Note: This example requires Chilkat v9.5.0.85 or greater.
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#include <C_CkPdf.h>
#include <C_CkJsonObject.h>
#include <C_CkCert.h>
void ChilkatSample(void)
{
BOOL success;
HCkPdf pdf;
HCkJsonObject json;
HCkCert cert;
HCkPdf pdf2;
success = FALSE;
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.
pdf = CkPdf_Create();
// Load a PDF to be signed.
// The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
success = CkPdf_LoadFile(pdf,"qa_data/pdf/hello.pdf");
if (success == FALSE) {
printf("%s\n",CkPdf_lastErrorText(pdf));
CkPdf_Dispose(pdf);
return;
}
// Options for signing are specified in JSON.
json = CkJsonObject_Create();
// In most cases, the signingCertificateV2 and signingTime attributes are required.
CkJsonObject_UpdateInt(json,"signingCertificateV2",1);
CkJsonObject_UpdateInt(json,"signingTime",1);
// When cryptographically signing a PDF, the signature's appearance can be placed on a specific
// page in the PDF document, and at a specified location on the page.
// The 1st page of the PDF document is page number 1 (we don't use 0-based numbering for PDF page numbers).
// The PDF object has a NumPages property, so we can use it to sign on the last page of the PDF.
CkJsonObject_UpdateInt(json,"page",CkPdf_getNumPages(pdf));
// appearance.y and appearance.x JSON properties control the x,y location of the signature.
// The "appearance.y" can be "top" or "bottom".
// The "appearance.x" can be "left", "middle", or "right".
// It is also possible to specify exact PDF location in user space coordinates, which is discussed below.
CkJsonObject_UpdateString(json,"appearance.y","bottom");
CkJsonObject_UpdateString(json,"appearance.x","middle");
// In this example, the fontScale (in combination with the number of appearance text lines and the length of the longest text line),
// automatically determine the width/height of the signature text box. Any included graphic (JPG image or built-in SVG) is automatically
// scaled to fit. It is alternatively possible to specify the desired width/height of the signature rectangle. In that case
// you would NOT specify a fontScale because Chilkat would automatically chose a font scale to fit the text to the desired rectangle.
// This example demonstrates how to specify the exact width/height of the PDF signature text box.
CkJsonObject_UpdateString(json,"appearance.fontScale","9.0");
CkJsonObject_UpdateString(json,"appearance.text[0]","Digitally signed by: cert_cn");
CkJsonObject_UpdateString(json,"appearance.text[1]","current_dt");
CkJsonObject_UpdateString(json,"appearance.image","document-accepted");
CkJsonObject_UpdateString(json,"appearance.imagePlacement","left");
CkJsonObject_UpdateString(json,"appearance.imageOpacity","100");
// Load the signing certificate. (Use your own certificate.)
cert = CkCert_Create();
success = CkCert_LoadPfxFile(cert,"qa_data/pfx/myPdfSigningCert.pfx","pfx_password");
if (success == FALSE) {
printf("%s\n",CkCert_lastErrorText(cert));
CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);
return;
}
// Tell the pdf object to use the certificate for signing.
success = CkPdf_SetSigningCert(pdf,cert);
if (success == FALSE) {
printf("%s\n",CkPdf_lastErrorText(pdf));
CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);
return;
}
success = CkPdf_SignPdf(pdf,json,"qa_output/hello_signed.pdf");
if (success == FALSE) {
printf("%s\n",CkPdf_lastErrorText(pdf));
CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);
return;
}
printf("The PDF has been successfully cryptographically signed.\n");
// The appearance of the signature appears in Adobe Acrobat as shown here:
// ----------------------------------------------------------------------------------------------------
// *** Scroll down for information about specifying the PDF signature x,y location in user space coordinates.
// ----------------------------------------------------------------------------------------------------
// (image:https://example-code.com/images/bottom_middle_signature.jpg/endImage)
// The x,y coordinates of a PDF page are in "user space", called "points", and there are 72 pointes per inch.
// A PDF page (8.5" x 11") is 612 points wide and 792 points high.
// The bottom left is at 0,0. The top right is at 612,792.
//
// To specify the location of a signature rectangle, the "appearance.y" is the y coordinate of the top of the signature rectangle,
// and the "appearance.x" is the x coordinate of the left of the signature rectangle.
// Therefore, to position the signature rectangle at the exact top/left of the page, we do this:
CkJsonObject_UpdateString(json,"appearance.y","792");
CkJsonObject_UpdateString(json,"appearance.x","0");
CkJsonObject_UpdateString(json,"appearance.text[0]","Digitally signed again by: cert_cn");
CkJsonObject_UpdateString(json,"appearance.text[1]","current_dt");
CkJsonObject_UpdateString(json,"appearance.image","document-accepted");
CkJsonObject_UpdateString(json,"appearance.imagePlacement","right");
pdf2 = CkPdf_Create();
success = CkPdf_LoadFile(pdf2,"qa_output/hello_signed.pdf");
success = CkPdf_SetSigningCert(pdf2,cert);
success = CkPdf_SignPdf(pdf2,json,"qa_output/hello_signed2.pdf");
if (success == FALSE) {
printf("%s\n",CkPdf_lastErrorText(pdf2));
CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);
CkPdf_Dispose(pdf2);
return;
}
printf("The PDF has been successfully cryptographically signed again.\n");
// Here we have the PDF with the signature just added at the exact top/left.
// (image:https://example-code.com/images/pdf_signature_top_left.jpg/endImage)
CkPdf_Dispose(pdf);
CkJsonObject_Dispose(json);
CkCert_Dispose(cert);
CkPdf_Dispose(pdf2);
}