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[US-800] Watermark examples. (#264)
* Watermark examples. * Simplified pdf_watermark_image.go * Updated unipdf version. * updated README.md
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‎go.mod‎

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@@ -13,7 +13,7 @@ require (
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github.com/unidoc/globalsign-dss v0.0.0-20220330092912-b69d85b63736
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github.com/unidoc/pkcs7 v0.2.0
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github.com/unidoc/unichart v0.3.0
16-
github.com/unidoc/unipdf/v3 v3.62.0
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github.com/unidoc/unipdf/v3 v3.65.0
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golang.org/x/crypto v0.31.0
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golang.org/x/image v0.18.0
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golang.org/x/text v0.21.0
@@ -50,7 +50,7 @@ require (
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github.com/unidoc/timestamp v0.0.0-20200412005513-91597fd3793a // indirect
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github.com/unidoc/unitype v0.4.0 // indirect
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go.opencensus.io v0.24.0 // indirect
53-
golang.org/x/net v0.24.0 // indirect
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golang.org/x/net v0.33.0 // indirect
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golang.org/x/oauth2 v0.7.0 // indirect
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golang.org/x/sys v0.28.0 // indirect
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golang.org/x/xerrors v0.0.0-20231012003039-104605ab7028 // indirect

‎go.sum‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -128,8 +128,8 @@ github.com/unidoc/timestamp v0.0.0-20200412005513-91597fd3793a h1:RLtvUhe4DsUDl6
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github.com/unidoc/timestamp v0.0.0-20200412005513-91597fd3793a/go.mod h1:j+qMWZVpZFTvDey3zxUkSgPJZEX33tDgU/QIA0IzCUw=
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github.com/unidoc/unichart v0.3.0 h1:VX1j5yzhjrR3f2flC03Yat6/WF3h7Z+DLEvJLoTGhoc=
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github.com/unidoc/unichart v0.3.0/go.mod h1:8JnLNKSOl8yQt1jXewNgYFHhFm5M6/ZiaydncFDpakA=
131-
github.com/unidoc/unipdf/v3 v3.62.0 h1:CVsxq6k1SSIrprotlFvq6iBhA+5745dWaApB0LKtGcc=
132-
github.com/unidoc/unipdf/v3 v3.62.0/go.mod h1:0OIzSHHno23Y8WzaK+852abK8d3AxUZ1GQkMqpyCzu8=
131+
github.com/unidoc/unipdf/v3 v3.65.0 h1:ye3PP9JuUJnQd4BqRR4wJO/EN9EpHRGusMOruDjCS74=
132+
github.com/unidoc/unipdf/v3 v3.65.0/go.mod h1:tTbloOTKtGGi6z5doJshesDpQYktePhR+7r+WGCkooU=
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github.com/unidoc/unitype v0.4.0 h1:/TMZ3wgwfWWX64mU5x2O9no9UmoBqYCB089LYYqHyQQ=
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github.com/unidoc/unitype v0.4.0/go.mod h1:HV5zuUeqMKA4QgYQq3KDlJY/P96XF90BQB+6czK6LVA=
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go.opencensus.io v0.24.0 h1:y73uSU6J157QMP2kn2r30vwW1A2W2WFwSCGnAVxeaD0=
@@ -153,8 +153,8 @@ golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn
153153
golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
154154
golang.org/x/net v0.0.0-20201110031124-69a78807bb2b/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
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golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd/go.mod h1:CfG3xpIq0wQ8r1q4Su4UZFWDARRcnwPjda9FqA0JpMk=
156-
golang.org/x/net v0.24.0 h1:1PcaxkF854Fu3+lvBIx5SYn9wRlBzzcnHZSiaFFAb0w=
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golang.org/x/net v0.24.0/go.mod h1:2Q7sJY5mzlzWjKtYUEXSlBWCdyaioyXzRB2RtU8KVE8=
156+
golang.org/x/net v0.33.0 h1:74SYHlV8BIgHIFC/LrYkOGIwL19eTYXQ5wc6TBuO36I=
157+
golang.org/x/net v0.33.0/go.mod h1:HXLR5J+9DxmrqMwG9qjGCxZ+zKXxBru04zlTvWlWuN4=
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golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
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golang.org/x/oauth2 v0.7.0 h1:qe6s0zUXlPX80/dITx3440hWZ7GwMwgDDyrSGTPJG/g=
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golang.org/x/oauth2 v0.7.0/go.mod h1:hPLQkd9LyjfXTiRohC/41GhcFqxisoUQ99sCUOHO9x4=

‎image/README.md‎

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Original file line numberDiff line numberDiff line change
@@ -9,4 +9,5 @@ Having the ability to play around with images allows for the creation of attract
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- [pdf_images_to_pdf.go](pdf_images_to_pdf.go) explains how to add multiple images in a PDF document, one image per page.
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- [pdf_list_images.go](pdf_list_images.go) explains how to list images in a PDF file. Passes through each page, goes through the content stream and finds instances of both. XObject Images and inline images. Also handles images referred within XObject Form content streams.
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- [pdf_watermark_image.go](pdf_watermark_image.go) explains how to add watermark image to each page of a PDF file.
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- [pdf_remove_watermark_image.go](pdf_remove_watermark_image.go) explains how to remove watermark image from a PDF file.
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- Image extraction example can be found in [../extract](extract) example subfolder.

‎image/pdf_remove_watermark_image.go‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,81 @@
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/*
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* Remove watermark image to each page of a PDF file.
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*
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* Run as: go run pdf_remove_watermark_image.go input.pdf output.pdf
5+
*/
6+
7+
package main
8+
9+
import (
10+
"fmt"
11+
"os"
12+
13+
"github.com/unidoc/unipdf/v3/common/license"
14+
"github.com/unidoc/unipdf/v3/model"
15+
)
16+
17+
func init() {
18+
// Make sure to load your metered License API key prior to using the library.
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// If you need a key, you can sign up and create a free one at https://cloud.unidoc.io
20+
err := license.SetMeteredKey(os.Getenv(`UNIDOC_LICENSE_API_KEY`))
21+
if err != nil {
22+
panic(err)
23+
}
24+
}
25+
26+
func main() {
27+
if len(os.Args) < 3 {
28+
fmt.Printf("go run pdf_remove_watermark_image.go input.pdf output.pdf\n")
29+
os.Exit(1)
30+
}
31+
32+
inputPath := os.Args[1]
33+
outputPath := os.Args[2]
34+
35+
pdfReader, f, err := model.NewPdfReaderFromFile(inputPath, nil)
36+
if err != nil {
37+
fmt.Printf("Error: %v\n", err)
38+
os.Exit(1)
39+
}
40+
defer f.Close()
41+
42+
numPages, err := pdfReader.GetNumPages()
43+
if err != nil {
44+
fmt.Printf("Error: %v\n", err)
45+
os.Exit(1)
46+
}
47+
48+
for i := 0; i < numPages; i++ {
49+
pageNum := i + 1
50+
51+
// Read the page.
52+
page, err := pdfReader.GetPage(pageNum)
53+
if err != nil {
54+
fmt.Printf("Error: %v\n", err)
55+
os.Exit(1)
56+
}
57+
58+
// For watermarks applied by Adobe, just pass nil as argument.
59+
// For custom watermarks use pdf_list_images.go to figure out the name of watermark object.
60+
err = page.RemoveWatermarkImage("Img1")
61+
if err != nil {
62+
fmt.Printf("Error: %v\n", err)
63+
os.Exit(1)
64+
}
65+
}
66+
67+
// Generate a PDFWriter from PDFReader.
68+
pdfWriter, err := pdfReader.ToWriter(nil)
69+
if err != nil {
70+
fmt.Printf("Error: %v\n", err)
71+
os.Exit(1)
72+
}
73+
74+
err = pdfWriter.WriteToFile(outputPath)
75+
if err != nil {
76+
fmt.Printf("Error: %v\n", err)
77+
os.Exit(1)
78+
}
79+
80+
fmt.Printf("Complete, see output file: %s\n", outputPath)
81+
}

‎image/pdf_watermark_image.go‎

Lines changed: 27 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -8,11 +8,11 @@ package main
88

99
import (
1010
"fmt"
11+
"image"
1112
"os"
1213

1314
"github.com/unidoc/unipdf/v3/common"
1415
"github.com/unidoc/unipdf/v3/common/license"
15-
"github.com/unidoc/unipdf/v3/creator"
1616
"github.com/unidoc/unipdf/v3/model"
1717
)
1818

@@ -49,13 +49,25 @@ func addWatermarkImage(inputPath string, outputPath string, watermarkPath string
4949
common.Log.Debug("Input PDF: %v", inputPath)
5050
common.Log.Debug("Watermark image: %s", watermarkPath)
5151

52-
c := creator.New()
52+
// Create the watermark image from file.
53+
wImgFile, err := os.Open(watermarkPath)
54+
if err != nil {
55+
return err
56+
}
57+
defer wImgFile.Close()
58+
59+
watermarkImg, _, err := image.Decode(wImgFile)
60+
if err != nil {
61+
return err
62+
}
5363

54-
watermarkImg, err := c.NewImageFromFile(watermarkPath)
64+
image, err := model.DefaultImageHandler{}.NewImageFromGoImage(watermarkImg)
5565
if err != nil {
5666
return err
5767
}
5868

69+
xImage, err := model.NewXObjectImageFromImage(image, nil, nil)
70+
5971
// Read the input pdf file.
6072
f, err := os.Open(inputPath)
6173
if err != nil {
@@ -82,21 +94,19 @@ func addWatermarkImage(inputPath string, outputPath string, watermarkPath string
8294
return err
8395
}
8496

85-
// Add to creator.
86-
c.AddPage(page)
87-
88-
watermarkImg.ScaleToWidth(c.Context().PageWidth)
89-
watermarkImg.SetPos(0, (c.Context().PageHeight-watermarkImg.Height())/2)
90-
watermarkImg.SetOpacity(0.5)
91-
_ = c.Draw(watermarkImg)
97+
// Add watermark with options.
98+
page.AddWatermarkImage(xImage, model.WatermarkImageOptions{Alpha: 0.5, FitToWidth: true})
9299
}
93100

94-
// Add reader outline tree to the creator.
95-
c.SetOutlineTree(pdfReader.GetOutlineTree())
96-
97-
// Add reader AcroForm to the creator.
98-
c.SetForms(pdfReader.AcroForm)
101+
// Generate a PDFWriter from PDFReader.
102+
pdfWriter, err := pdfReader.ToWriter(nil)
103+
if err != nil {
104+
return err
105+
}
99106

100-
err = c.WriteToFile(outputPath)
101-
return err
107+
err = pdfWriter.WriteToFile(outputPath)
108+
if err != nil {
109+
return err
110+
}
111+
return nil
102112
}

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