Objective-C

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. Objective-C

#import <CkoPdf.h>
#import <CkoJsonObject.h>
#import <CkoCert.h>

BOOL success = NO;

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

CkoPdf *pdf = [[CkoPdf alloc] init];

// 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 == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

// Options for signing are specified in JSON.
CkoJsonObject *json = [[CkoJsonObject alloc] init];

// In most cases, the signingCertificateV2 and signingTime attributes are required.
[json UpdateInt: @"signingCertificateV2" value: [NSNumber numberWithInt: 1]];
[json UpdateInt: @"signingTime" value: [NSNumber numberWithInt: 1]];

// Put the signature on page 1, top left
[json UpdateInt: @"page" value: [NSNumber numberWithInt: 1]];
[json UpdateString: @"appearance.y" value: @"top"];
[json UpdateString: @"appearance.x" value: @"left"];

// Add some text.
[json UpdateString: @"appearance.text[0]" value: @"Digitally signed by: cert_cn"];
[json UpdateString: @"appearance.text[1]" value: @"current_dt"];

// Add a built-in SVG graphic to the right.
[json UpdateString: @"appearance.image" value: @"blue-check-mark"];
[json UpdateString: @"appearance.imagePlacement" value: @"right"];
[json UpdateString: @"appearance.imageOpacity" value: @"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" value: [NSNumber numberWithInt: (72 * 3)]];
[json UpdateInt: @"appearance.height" value: [NSNumber numberWithInt: 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. 
// (image:https://example-code.com/images/explicit_width_height.jpg/endImage)

// 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" value: [NSNumber numberWithInt: (72 * 4)]];
[json UpdateString: @"appearance.height" value: @"auto"];

// The signature would have this appearance: 
// (image:https://example-code.com/images/explicit_width_auto_height.jpg/endImage)

// 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" value: @"auto"];
[json UpdateInt: @"appearance.height" value: [NSNumber numberWithInt: 72]];

// The signature would have this appearance.
// (image:https://example-code.com/images/explicit_height_auto_width.jpg/endImage)

// 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.

CkoJsonObject *jAppearance = [[CkoJsonObject alloc] init];
[json ObjectOf2: @"appearance" jsonObj: jAppearance];

[jAppearance Delete: @"width"];
[jAppearance Delete: @"height"];
[json UpdateString: @"appearance.fontScale" value: @"10.0"];

// With fontScale = "10.0"
// (image:https://example-code.com/images/font_scale_10.jpg/endImage)

// Load the signing certificate. (Use your own certificate.)
CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadPfxFile: @"qa_data/pfx/myPdfSigningCert.pfx" password: @"pfx_password"];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// Tell the pdf object to use the certificate for signing.
success = [pdf SetSigningCert: cert];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

success = [pdf SignPdf: json outFilePath: @"qa_output/hello_signed.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

NSLog(@"%@",@"The PDF has been successfully cryptographically signed.");