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pdf_annotate_add_text.go
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pdf_annotate_add_text.go
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/*
* Annotate/mark up pages of a PDF file.
* Adds a text annotation with a user specified string to a fixed location on every page.
*
* Run as: go run pdf_annotate_add_text.go input.pdf output.pdf text
*/
package main
import (
"fmt"
"os"
"github.com/unidoc/unipdf/v3/common/license"
"github.com/unidoc/unipdf/v3/core"
"github.com/unidoc/unipdf/v3/model"
)
func init() {
// Make sure to load your metered License API key prior to using the library.
// If you need a key, you can sign up and create a free one at https://cloud.unidoc.io
err := license.SetMeteredKey(os.Getenv(`UNIDOC_LICENSE_API_KEY`))
if err != nil {
panic(err)
}
}
func main() {
if len(os.Args) < 4 {
fmt.Printf("go run pdf_annotate_add_text.go input.pdf output.pdf text\n")
os.Exit(1)
}
inputPath := os.Args[1]
outputPath := os.Args[2]
annotationText := os.Args[3]
err := annotatePdfAddText(inputPath, outputPath, annotationText)
if err != nil {
fmt.Printf("Error: %v\n", err)
os.Exit(1)
}
fmt.Printf("Complete, see output file: %s\n", outputPath)
}
// Annotate pdf file.
func annotatePdfAddText(inputPath string, outputPath string, annotationText string) error {
// Read the input pdf file.
f, err := os.Open(inputPath)
if err != nil {
return err
}
defer f.Close()
pdfReader, err := model.NewPdfReader(f)
if err != nil {
return err
}
// Process each page using the following callback
// when generating PdfWriter.
opt := &model.ReaderToWriterOpts{
PageProcessCallback: func(pageNum int, page *model.PdfPage) error {
// New text annotation.
textAnnotation := model.NewPdfAnnotationText()
textAnnotation.Contents = core.MakeString(annotationText)
// The rect specifies the location of the markup.
textAnnotation.Rect = core.MakeArray(core.MakeInteger(20), core.MakeInteger(100), core.MakeInteger(10+50), core.MakeInteger(100+50))
// Add to the page annotations.
page.AddAnnotation(textAnnotation.PdfAnnotation)
return nil
},
}
// Generate a PdfWriter instance from existing PdfReader.
pdfWriter, err := pdfReader.ToWriter(opt)
if err != nil {
return err
}
// Write to file.
err = pdfWriter.WriteToFile(outputPath)
if err != nil {
return err
}
return nil
}