Watermarks in Flutter PDF

10 Oct 20222 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();