Watermarks in Flutter PDF

14 Dec 20242 minutes to read

The Syncfusion^® Flutter PDF provides support for adding watermarks to a PDF document using PdfGraphics.

Adding text watermark to a PDF document

The Syncfusion^® Flutter PDF allows you draw the text watermark to the PDF document using graphics elements.

The following code example explains how to draw the text watermark to the PDF document.

//Create a new PDF document
PdfDocument document = PdfDocument();

//Add a page to the document and get page graphics
PdfGraphics graphics = document.pages.add().graphics;

//Watermark text
PdfGraphicsState state = graphics.save();

//Set transparency and rotation 
graphics.setTransparency(0.25);

graphics.rotateTransform(-40);

//Add text watermark 
graphics.drawString('Imported using Essential PDF',
    PdfStandardFont(PdfFontFamily.helvetica, 20),
    pen: PdfPens.red,
    brush: PdfBrushes.red,
    bounds: Rect.fromLTWH(-150, 450, 0, 0));

//Restore graphics state
graphics.restore(state);

//Save and dispose the PDF document
File('SampleOutput.pdf').writeAsBytes(await document.save());
document.dispose();

Adding image watermark to a PDF document

To add the image watermark to a PDF document, you can draw the image with transparency in PdfGraphics.

The following code example explains how to draw an image watermark to the PDF document.

DART

//Create a new PDF document
PdfDocument document = PdfDocument();

//Add a page to the document and get page graphics
PdfGraphics graphics = document.pages.add().graphics;

//Get image data
File imageFile = File('image.jpg'); 
Uint8List imagebytes = await imageFile.readAsBytes();
String imageBase64 = base64.encode(imagebytes);

//Watermark image
PdfGraphicsState state = graphics.save();
graphics.setTransparency(0.25);
graphics.drawImage(
    PdfBitmap.fromBase64String(imageBase64),
    Rect.fromLTWH(
        0, 0, graphics.clientSize.width, graphics.clientSize.height));
graphics.restore(state);

//Save and dispose the PDF document
File('SampleOutput.pdf').writeAsBytes(await document.save());
document.dispose();