feat(pdfengines): add watermark and stamp feature

pkg/modules/libreoffice/api/api.go

@@ -147,6 +147,29 @@ type Options struct {
 	// Possible values are: 75, 150, 300, 600 and 1200.
 	MaxImageResolution int
 
+	// NativeWatermarkText specifies the text for a watermark to be drawn on
+	// every page of the exported PDF file.
+	// See https://help.libreoffice.org/latest/en-US/text/shared/guide/pdf_params.html.
+	NativeWatermarkText string
+
+	// NativeWatermarkColor specifies the color for the watermark text as a
+	// decimal long value. Default is 8388223 (light green).
+	NativeWatermarkColor int
+
+	// NativeWatermarkFontHeight specifies the font size for the watermark text.
+	NativeWatermarkFontHeight int
+
+	// NativeWatermarkRotateAngle specifies the rotation angle for the watermark
+	// text in tenths of a degree (e.g., 450 = 45°).
+	NativeWatermarkRotateAngle int
+
+	// NativeWatermarkFontName specifies the font name for the watermark text.
+	// Default is "Helvetica".
+	NativeWatermarkFontName string
+
+	// NativeTiledWatermarkText specifies the tiled watermark text.
+	NativeTiledWatermarkText string
+
 	// PdfFormats allows to convert the resulting PDF to PDF/A-1b, PDF/A-2b,
 	// PDF/A-3b and PDF/UA.
 	PdfFormats gotenberg.PdfFormats
@@ -178,6 +201,12 @@ func DefaultOptions() Options {
 		Quality:                         90,
 		ReduceImageResolution:           false,
 		MaxImageResolution:              300,
+		NativeWatermarkText:             "",
+		NativeWatermarkColor:            8388223,
+		NativeWatermarkFontHeight:       0,
+		NativeWatermarkRotateAngle:      0,
+		NativeWatermarkFontName:         "Helvetica",
+		NativeTiledWatermarkText:        "",
 		PdfFormats: gotenberg.PdfFormats{
 			PdfA:  "",
 			PdfUa: false,

pkg/modules/libreoffice/api/libreoffice.go

@@ -302,6 +302,30 @@ func (p *libreOfficeProcess) pdf(ctx context.Context, logger *zap.Logger, inputP
 	args = append(args, "--export", fmt.Sprintf("ReduceImageResolution=%t", options.ReduceImageResolution))
 	args = append(args, "--export", fmt.Sprintf("MaxImageResolution=%d", options.MaxImageResolution))
 
+	if options.NativeWatermarkText != "" {
+		args = append(args, "--export", fmt.Sprintf("Watermark=%s", options.NativeWatermarkText))
+	}
+
+	if options.NativeWatermarkColor != 0 {
+		args = append(args, "--export", fmt.Sprintf("WatermarkColor=%d", options.NativeWatermarkColor))
+	}
+
+	if options.NativeWatermarkFontHeight > 0 {
+		args = append(args, "--export", fmt.Sprintf("WatermarkFontHeight=%d", options.NativeWatermarkFontHeight))
+	}
+
+	if options.NativeWatermarkRotateAngle != 0 {
+		args = append(args, "--export", fmt.Sprintf("WatermarkRotateAngle=%d", options.NativeWatermarkRotateAngle))
+	}
+
+	if options.NativeWatermarkFontName != "" && options.NativeWatermarkFontName != "Helvetica" {
+		args = append(args, "--export", fmt.Sprintf("WatermarkFontName=%s", options.NativeWatermarkFontName))
+	}
+
+	if options.NativeTiledWatermarkText != "" {
+		args = append(args, "--export", fmt.Sprintf("TiledWatermark=%s", options.NativeTiledWatermarkText))
+	}
+
 	switch options.PdfFormats.PdfA {
 	case "":
 	case gotenberg.PdfA1b:

pkg/modules/libreoffice/pdfengine/pdfengine.go

@@ -116,6 +116,16 @@ func (engine *LibreOfficePdfEngine) EmbedFiles(ctx context.Context, logger *zap.
 	return fmt.Errorf("embed files with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// Watermark is not available in this implementation.
+func (engine *LibreOfficePdfEngine) Watermark(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+	return fmt.Errorf("watermark PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// Stamp is not available in this implementation.
+func (engine *LibreOfficePdfEngine) Stamp(ctx context.Context, logger *zap.Logger, inputPath string, stamp gotenberg.Stamp) error {
+	return fmt.Errorf("stamp PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*LibreOfficePdfEngine)(nil)

pkg/modules/libreoffice/routes.go

@@ -32,6 +32,10 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 			metadata := pdfengines.FormDataPdfMetadata(form, false)
 			userPassword, ownerPassword := pdfengines.FormDataPdfEncrypt(form)
 			embedPaths := pdfengines.FormDataPdfEmbeds(form)
+			watermark := pdfengines.FormDataPdfWatermark(form, false)
+			watermarkFiles := pdfengines.FormDataPdfWatermarkFiles(form)
+			stamp := pdfengines.FormDataPdfStamp(form, false)
+			stampFiles := pdfengines.FormDataPdfStampFiles(form)
 
 			zeroValuedSplitMode := gotenberg.SplitMode{}
 
@@ -60,6 +64,12 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				quality                         int
 				reduceImageResolution           bool
 				maxImageResolution              int
+				nativeWatermarkText             string
+				nativeWatermarkColor            int
+				nativeWatermarkFontHeight       int
+				nativeWatermarkRotateAngle      int
+				nativeWatermarkFontName         string
+				nativeTiledWatermarkText        string
 				nativePdfFormats                bool
 				merge                           bool
 				flatten                         bool
@@ -128,6 +138,48 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 					maxImageResolution = intValue
 					return nil
 				}).
+				String("nativeWatermarkText", &nativeWatermarkText, defaultOptions.NativeWatermarkText).
+				Custom("nativeWatermarkColor", func(value string) error {
+					if value == "" {
+						nativeWatermarkColor = defaultOptions.NativeWatermarkColor
+						return nil
+					}
+					intValue, err := strconv.Atoi(value)
+					if err != nil {
+						return err
+					}
+					nativeWatermarkColor = intValue
+					return nil
+				}).
+				Custom("nativeWatermarkFontHeight", func(value string) error {
+					if value == "" {
+						nativeWatermarkFontHeight = defaultOptions.NativeWatermarkFontHeight
+						return nil
+					}
+					intValue, err := strconv.Atoi(value)
+					if err != nil {
+						return err
+					}
+					if intValue < 0 {
+						return errors.New("value is inferior to 0")
+					}
+					nativeWatermarkFontHeight = intValue
+					return nil
+				}).
+				Custom("nativeWatermarkRotateAngle", func(value string) error {
+					if value == "" {
+						nativeWatermarkRotateAngle = defaultOptions.NativeWatermarkRotateAngle
+						return nil
+					}
+					intValue, err := strconv.Atoi(value)
+					if err != nil {
+						return err
+					}
+					nativeWatermarkRotateAngle = intValue
+					return nil
+				}).
+				String("nativeWatermarkFontName", &nativeWatermarkFontName, defaultOptions.NativeWatermarkFontName).
+				String("nativeTiledWatermarkText", &nativeTiledWatermarkText, defaultOptions.NativeTiledWatermarkText).
 				Bool("nativePdfFormats", &nativePdfFormats, true).
 				Bool("merge", &merge, false).
 				Bool("flatten", &flatten, false).
@@ -136,6 +188,13 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
+			if (watermark.Source == gotenberg.StampSourceImage || watermark.Source == gotenberg.StampSourcePDF) && len(watermarkFiles) > 0 {
+				watermark.Expression = watermarkFiles[0]
+			}
+			if (stamp.Source == gotenberg.StampSourceImage || stamp.Source == gotenberg.StampSourcePDF) && len(stampFiles) > 0 {
+				stamp.Expression = stampFiles[0]
+			}
+
 			outputPaths := make([]string, len(inputPaths))
 			for i, inputPath := range inputPaths {
 				outputPaths[i] = ctx.GeneratePath(".pdf")
@@ -163,6 +222,12 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 					Quality:                         quality,
 					ReduceImageResolution:           reduceImageResolution,
 					MaxImageResolution:              maxImageResolution,
+					NativeWatermarkText:             nativeWatermarkText,
+					NativeWatermarkColor:            nativeWatermarkColor,
+					NativeWatermarkFontHeight:       nativeWatermarkFontHeight,
+					NativeWatermarkRotateAngle:      nativeWatermarkRotateAngle,
+					NativeWatermarkFontName:         nativeWatermarkFontName,
+					NativeTiledWatermarkText:        nativeTiledWatermarkText,
 				}
 
 				if nativePdfFormats && splitMode == zeroValuedSplitMode {
@@ -253,6 +318,16 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				}
 			}
 
+			err = pdfengines.WatermarkStub(ctx, engine, watermark, outputPaths)
+			if err != nil {
+				return fmt.Errorf("watermark PDFs: %w", err)
+			}
+
+			err = pdfengines.StampStub(ctx, engine, stamp, outputPaths)
+			if err != nil {
+				return fmt.Errorf("stamp PDFs: %w", err)
+			}
+
 			err = pdfengines.EmbedFilesStub(ctx, engine, embedPaths, outputPaths)
 			if err != nil {
 				return fmt.Errorf("embed files into PDFs: %w", err)