Showing image on a acro text field position

问题

I had a PDF document which has acro text fields which is already shared to the client. Now the client wants to insert signature image in one of the text fields. My manager asked me to try a way to do the same.My idea is to replace an image on top of the text field position and resize the text field as image size.

For replacing acro text field of pdf into image, i am trying as below

1.Finding the text field by its field id 

String position = null; 
List<FieldPosition> fieldPositons = form.getFieldPositions("50106");
                    for (FieldPosition position :fieldPositons) {
                        this.position = position.position;
                    }
2. Setting the image into that position of text field
     Image image = Image.getInstance("ImageFileName");
Float dimensions = position.split("x");
image.setAbsolutePosition(dimensions[0], dimensions[1]);    
content.addImage(image);

Based on the given image width and height i need to change the width and height of acro text field.

Can any one tried as below, Is my logic works with itext pdf library. Let me know if any idea to replace acro text field with image

回答1:

It is never a good idea to change the dimensions of an AcroField as all the content in a PDF is added at absolute positions. When you change the dimension of a field, you risk that it will overlap with other content.

Hence, your best option is to adapt the size of the image to the size of the AcroField. As you already indicated, you can get the field position like this:

AcroFields.FieldPosition f = form.GetFieldPositions("50106")[0];

Note that it's not a good idea to make this a string. You can use the FieldPosition object like this:

int page = f.page;
Rectangle rect = f.position;

You can scale and position the image like this:

Image image = Image.getInstance("ImageFileName");
image.ScaleToFit(rect.Width, rect.Height);
image.SetAbsolutePosition(rect.Left, rect.Bottom);

The ScaleToFit() method will scale the image in such a way that it will fit the dimensions of the form field, respecting the original aspect ratio of the image (you don't want to add a stretched image).

You need to page variable to add the image to the correct page:

PdfContentByte canvas = stamper.GetOverContent(page);
canvas.AddImage(image);

Important:

• If you add the image as described above, you need to remove the field (this happens automatically if you flatten the form).
• If the form field is a button, then you shouldn't use the above code. Instead you should replace the icon of the button. This is described in my answer to the question How to change a Button Icon of a PDF Formular with itextsharp? This answer explains the standard way to do what you're trying to do, but it requires that the field where you want to add the image is a button field (and based on your question, it seems that it's a text field).

来源：https://stackoverflow.com/questions/33596564/showing-image-on-a-acro-text-field-position