rotate image signature in acro_form

[WSPDV]

hi, mas @gettalong I am stuck on the rotation image using the signature field. There is no error, but the signature image does not appear in the result.

        field = @doc.acro_form(create: true) .create_signature_field(SecureRandom.uuid)

        widget = field.create_widget(@doc.pages[0], defaults: false, Rect: [0, 0, 364, 146], rotation: 90)
        image = widget.create_appearance
                      .canvas
                      .xobject(@image_path, at: [0, 0], width: 364, height: 146)
        image[:Resources] = {}

[gettalong]

Please have a look at https://hexapdf.gettalong.org/documentation/api/HexaPDF/Type/AcroForm/Field/index.html#method-i-create_widget - the :rotation key is not a valid dictionary entry for a widget annotation.

If you want to rotate the image, you should use the rotated image size in the Rect value and use the canvas.rotate command before placing the image.

[WSPDV]

 widget = field.create_widget(@page, defaults: false, Rect: [0, 0, 146, 364])
        image = widget.create_appearance
                      .canvas.rotate(90)
                      .xobject(@image_path, at: [0, 0], width: 146, height: 364)
        image[:Resources] = {}
        field

rotate like this @gettalong ?

the Rect is correct but the image is still not appear

[gettalong]

Can you please provide a complete sample script that shows the problem?

FYI: The rect you specify is in the lower-left corner of the page, is that correct?

[WSPDV]

this is a picture of signature

and this is a full code

class Trial4
      require 'hexapdf'
      require HexaPDF.data_dir + '/cert/demo_cert.rb'

      def initialize(pdf_path)
        @signed_pdf_path = "tmp/img_signed_#{Time.now.to_i}.pdf"
        @pdf_path = pdf_path
        @doc = HexaPDF::Document.open(pdf_path)
        @image_path = 'spec/fixtures/files/signature.png'
      end

      def call
        @doc.sign(@signed_pdf_path, reason: 'Some reason',
                                    location: 'Hatimu',
                                    contact_info: 'wspdv@tampan.coeg',
                                    signature: field_signature,
                                    certificate: HexaPDF.demo_cert.cert,
                                    key: HexaPDF.demo_cert.key,
                                    certificate_chain: [HexaPDF.demo_cert.sub_ca,
                                                        HexaPDF.demo_cert.root_ca])
      end

      def image
        @image ||= Magick::Image.read(@image_path).first
      end

      def field_signature
        field = @doc.acro_form(create: true)
                    .create_signature_field('AQ')

        widget = field.create_widget(@doc.pages[0], defaults: false,
                                                    Rect: [0, 0, image.columns, image.rows])
        img_sig = widget.create_appearance
                        .canvas
                        .xobject(@image_path, at: [0, 0], width: image.columns, height: image.rows)
        img_sig[:Resources] = {}
        field
      end
    end

and the result like below (this coordinate is expected because I set the coordinate in 0, 0 in the document that has 180 rotate). see the picture of the signature (the picture is rotated, different from the original picture).

i want to set the rotation image (the position image kept like an original picture). then i wrote code like this (override the method field_signature)

      def field_signature
        field = @doc.acro_form(create: true)
                    .create_signature_field('AQ')

        widget = field.create_widget(@doc.pages[0], defaults: false,
                                                    Rect: [0, 0, image.columns, image.rows])
        img_sig = widget.create_appearance
                        .canvas.rotate(180)
                        .xobject(@image_path, at: [0, 0], width: image.columns, height: image.rows)
        img_sig[:Resources] = {}
        field
      end

then the result is image does not appear

[gettalong]

So the problem here is that once the canvas is rotated, everything is upside down, including the coordinate system. So the positive x direction will now go to the left and the positive y direction will now go down. And note that the origin did not change its location, it is still at the bottom-left corner of the rectangle. To remedy that you need to move the origin to the upper-right corner.

Here is an example:

require 'hexapdf'

doc = HexaPDF::Document.new
canvas = doc.pages.add([0, 0, 200, 200]).canvas
canvas.save_graphics_state do
  canvas.stroke_color("grey").line_width(0.5).
    line(100, 0, -100, 0).line(0, -100, 0, 100).stroke
end
canvas.rotate(180) do
  canvas.rectangle(0, 0, 80, 40).stroke
end
canvas.rotate(180) do
  canvas.translate(-200, -200) # move origin to the upper-right corner
  canvas.stroke_color("hp-blue").
    rectangle(0, 0, 80, 40).stroke
end
doc.write('rotation.pdf')

Here is the result:

You can only see the second rectangle, the blue one, in the image because the other one, the first one, is out of view below the bottom-left corner.

In your case you would need to use .rotate(180).translate(image.columns, image.rows).

[WSPDV]

if using canvas means can break the PDF content, I already have a code using canvas, and it works. so I need it for the signature field only.

i already added the code that you suggested, but the image still not showing

def field_signature
        field = @doc.acro_form(create: true)
                    .create_signature_field('AQ')

        widget = field.create_widget(@doc.pages[0], defaults: false,
                                                    Rect: [0, 0, image.rows, image.columns])
        img_sig = widget.create_appearance
                        .canvas
                        .rotate(270).translate(image.rows, image.columns)
                        .xobject(@image_path, at: [0, 0], width: image.rows, height: image.columns)
        img_sig[:Resources] = {}
        field
      end

if without .rotate(270).translate(image.rows, image.columns)

image showing, but the rotation for the image is not true.

I need the image still like the original

like this

[gettalong]

If you rotate by 270 degrees, you have to adjust the translation arguments as well as the width/height arguments for the #xobject call.

You might also need to use the :no_rotate flag, i.e. widget.flag(:no_rotate) to avoid the viewer rotating the annotation if the page has the /Rotate key set.

[WSPDV]

translation argument height and width are correct when I click on the signature panel, it will show the box where the signature is placed (only the dots in frame) like the picture below (in the bottom right). I assumed this is already correct.

for this is code -> widget.flag(:no_rotate) where is the right placed ? I already added widget.flag(:no_rotate) after create_widget:

        field = @doc.acro_form(create: true)
                    .create_signature_field('AQ')

        widget = field.create_widget(@doc.pages[0], defaults: false, Rect: [0, 0, 512, 908], flag: :no_rotate)
        widget.flag(:no_rotate)

        image = widget.create_appearance
                      .canvas
                      .xobject(image_signature, at: [0, 0])

        widget.flag(:no_rotate)
        field

but the image is still now shown. I also tried to larger the width and height of the signature field (to be full of pages), and try rearrange this section -> .xobject(image_signature, at: [100, 100]) but still not appear

[gettalong]

Here is a self-contained example based on your code:

require 'hexapdf'
require HexaPDF.data_dir + '/cert/demo_cert.rb'

doc = HexaPDF::Document.new
doc.pages.add.canvas.
  font("Helvetica", size: 10).
  text("Top-left", at: [20, 800])
doc.pages[0].rotate(180)

image = doc.add({Type: :XObject, Subtype: :Form, BBox: [0, 0, 200, 100]})
image.canvas.font("Helvetica", size: 10).text('Signature', at: [20, 20])

field = doc.acro_form(create: true).create_signature_field('AQ')
widget = field.create_widget(doc.pages[0], defaults: false,
                                            Rect: [0, 0, image.width, image.height])
img_sig = widget.create_appearance.
                canvas.
                save_graphics_state.fill_color("ffddff").rectangle(0, 0, image.width, image.height).fill.restore_graphic_state.
                xobject(image, at: [0, 0], width: image.width, height: image.height)
img_sig[:Resources] = {}

doc.sign('signed.pdf', reason: 'Some reason',
                            location: 'Hatimu',
                            contact_info: 'wspdv@tampan.coeg',
                            signature: field,
                            certificate: HexaPDF.demo_cert.cert,
                            key: HexaPDF.demo_cert.key,
                            certificate_chain: [HexaPDF.demo_cert.sub_ca,
                                                HexaPDF.demo_cert.root_ca])

resulting in this:

• In this case the :no_rotate flag is not needed. If you still use it, the signature widget annotation will still be at the top-right of the page (i.e. where (0,0) is located) but extends to the left and top, out of the bounds of the page.

• You can use image.width and image.height to get the width and height of the image, so no need to use Magick::Image.

• If you want to have the signature widget correctly rotated, you need to insert rotate(180).translate(-image.width, -image.height). after the canvas. call. This will then result in this:

• If the page has another rotation, you will need to appropriately size the widget and rotate and translate the canvas before placing the image. You could also just call page.rotate(0, flatten: true) before doing anything to remove the /Rotate key from the page and embed the rotation into the content stream. This could make it easier for you to place the signature field.

[WSPDV]

Thanks, mas @gettalong

the simple choice is using page.rotate(0, flatten: true) but if the document already has a certificate, it will break the certificate before, because it will modify the content/page.

i already tried that and I also tried use rotate(180).translate(-image.width, -image.height). the second is work (not breaking the certificate before if the document has a certificate). Could you let me know the rules/formula for the value from .translate().?

[gettalong]

The rules are just basic geometry. You can visualize it:

require 'hexapdf'

doc = HexaPDF::Document.new
canvas = doc.pages.add.canvas
canvas.font('Helvetica', size: 8)
iw, ih = 100, 60
[0, 90, 180, 270].each_with_index do |rotation, index|
  canvas.save_graphics_state do
    # Simulate page rotation
    canvas.translate(220, 700 - index * 150)
    canvas.rotate(rotation)
    canvas.rectangle(0, 0, iw, ih).stroke
    canvas.text("Text", at: [5, 5])
    canvas.fill_color("hp-blue").circle(0, 0, 2).fill

    case rotation
    when 0 then #nothing
    when 90 then canvas.rotate(-90).translate(-ih, 0)
    when 180 then canvas.rotate(-180).translate(-iw, -ih)
    when 270 then canvas.rotate(-270).translate(0, -iw)
    end
    canvas.fill_color("hp-orange").circle(0, 0, 2).fill
    canvas.stroke_color("hp-teal").rectangle(0, 0, iw, ih).stroke
    canvas.text("Text", at: [5, 5])
  end
end
doc.write('visualize.pdf')

The result is this: visualize.pdf

[WSPDV]

Your answer is very helpful. I will try in my local. Hopefully, it can work. I'll close this discussion. Thank you mas @gettalong 🙏🏿