Python: Add Image Watermarks to PDF Documents

Image watermarks are frequently found on shared documents. Unlike text watermarks, image watermarks provide a simpler and less intrusive way to emphasize copyright, ownership, and confidentiality by displaying company logos, trademarks, warning icons, etc. In addition, adding image watermarks to PDF documents can also help brand promotion and enhance the visual appeal of the documents. This article will explain how to insert image watermarks to PDF documents using Spire.PDF for Python in Python programs.

• Add Single Image Watermarks to PDF Documents
• Add Repeating Image Watermarks to PDF Documents

Install Spire.PDF for Python

This scenario requires Spire.PDF for Python and plum-dispatch v1.7.4. They can be easily installed in your Windows through the following pip commands.

pip install Spire.PDF

If you are unsure how to install, please refer to this tutorial: How to Install Spire.PDF for Python on Windows

Add Single Image Watermarks to PDF Documents

Single image watermarks are transparent images at the center of PDF pages. With Spire.PDF for Python, users can draw a specified image as a watermark on any PDF page. The detailed steps are as follows:

• Create an object of PdfDocument class.
• Load a PDF document using PdfDocument.LoadFromFile() method.
• Load the watermark image using PdfImage.FromFile() method.
• Loop through the pages in the document to add the watermark.
• Get a page using PdfDocument.Pages.get_Item() method.
• Set the transparency of the watermark using PdfPageBase.Canvas.SetTransparency() method.
• Draw the watermark image in the center of the page using PdfPageBase.Canvas.DrawImage() method.
• Save the document using PdfDocument.SaveToFile() method.

from spire.pdf import *
from spire.pdf.common import *

# Create an object of PdfDocument class
pdf = PdfDocument()

# Load a PDF document
pdf.LoadFromFile("Sample.pdf")

# Load the watermark image
image = PdfImage.FromFile("watermark.png")

# Get the width and height of the image
imageWidth = float(image.Width)
imageHeight = float(image.Height)

# Loop through the pages in the document
for i in range(pdf.Pages.Count):
    # Get a page
    page = pdf.Pages.get_Item(i)
    # Set the transparency of the watermark
    page.Canvas.SetTransparency(0.3)
    # Get the width and height of the page
    pageWidth = page.ActualSize.Width
    pageHeight = page.ActualSize.Height
    # Draw the watermark image on the page
    page.Canvas.DrawImage(image, pageWidth/2 - imageWidth/2, pageHeight/2 - imageHeight/2, imageWidth, imageHeight)

# Save the document
pdf.SaveToFile("output/SingleImageWatermark.pdf")
pdf.Close()

Add Repeating Image Watermarks to PDF Documents

Repeating image watermarks are images repeated regularly on PDF pages. Drawing repeated image watermarks on PDF pages with Spire.PDF for Python involves the use of the PdfTillingBrush class. Below are the detailed steps:

• Create an object of PdfDocument class.
• Load a PDF document using PdfDocument.LoadFromFile() method.
• Load the watermark image using PdfImage.FromFile() method.
• Loop through the pages in the document to add the watermark.
• Get a page using PdfDocument.Pages.get_Item() method.
• Create an object of PdfTilingBrush class and set its size to determine the number of repetitions of the watermark.
• Set the transparency of the watermark using PdfTillingBrush.Graphics.SetTransparency() method.
• Translate the coordinate system to the specified position using PdfTillingBrush.Graphics.TranslateTransform() method to make the watermark displayed in the center of each repetition.
• Draw the watermark image on the tilling brush using PdfTillingBrush.Graphics.DrawImage() method.
• Draw the watermark on the page using PdfPageBase.Canvas.DrawRectangle() method.
• Save the document using PdfDocument.SaveToFile() method.

from spire.pdf.common import *
from spire.pdf import *

# Create an object of PdfDocument class
pdf = PdfDocument()

# Load a PDF document
pdf.LoadFromFile("Sample.pdf")

# Load the watermark image
image = PdfImage.FromFile("watermark.png")

# Loop through the pages of the document
for i in range(pdf.Pages.Count):
    # Get a page
    page = pdf.Pages.get_Item(i)
    # Create an object of PdfTilingBrush class and set its size
    brush = PdfTilingBrush(SizeF(page.Canvas.Size.Width / float(3), page.Canvas.Size.Height / float(3)))
    # Set the transparency of the watermark
    brush.Graphics.SetTransparency(0.3)
    brush.Graphics.Save()
    # Translate the coordinate to the specified position
    brush.Graphics.TranslateTransform(brush.Size.Width/2 - image.Width/2, brush.Size.Height/2 - image.Height/2)
    # Draw the watermark image on the brush
    brush.Graphics.DrawImage(image, 0.0, 0.0, float(image.Width), float(image.Height))
    brush.Graphics.Restore()
    # Draw the watermark on the page
    page.Canvas.DrawRectangle(brush, RectangleF(PointF(0.0, 0.0), page.Canvas.Size))

# Save the PDF document
pdf.SaveToFile("output/RepeatingImageWatermark.pdf", FileFormat.PDF)
pdf.Close()

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