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pdf_rotate.go
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pdf_rotate.go
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/*
* Rotate pages in a PDF file. Degrees needs to be a multiple of 90.
* Example of how to manipulate pages with the pdf creator.
*
* Run as: go run pdf_rotate.go output.pdf <angle> input.pdf
* The angle is specified in degrees.
*/
package main
import (
"errors"
"fmt"
"os"
"strconv"
unicommon "github.com/unidoc/unipdf/v3/common"
"github.com/unidoc/unipdf/v3/creator"
pdf "github.com/unidoc/unipdf/v3/model"
)
func init() {
// Use debug-mode log level.
unicommon.SetLogger(unicommon.NewConsoleLogger(unicommon.LogLevelDebug))
}
func main() {
if len(os.Args) < 4 {
fmt.Printf("Usage: go run pdf_rotate.go input.pdf <angle> output.pdf\n")
os.Exit(1)
}
inputPath := os.Args[1]
outputPath := os.Args[3]
degrees, err := strconv.ParseInt(os.Args[2], 10, 64)
if err != nil {
fmt.Printf("Invalid degrees: %v\n", err)
os.Exit(1)
}
if degrees%90 != 0 {
fmt.Printf("Degrees needs to be a multiple of 90\n")
os.Exit(1)
}
err = rotatePdf(inputPath, degrees, outputPath)
if err != nil {
fmt.Printf("Error: %v\n", err)
os.Exit(1)
}
fmt.Printf("Complete, see output file: %s\n", outputPath)
}
// Rotate all pages by 90 degrees.
func rotatePdf(inputPath string, degrees int64, outputPath string) error {
c := creator.New()
f, err := os.Open(inputPath)
if err != nil {
return err
}
defer f.Close()
pdfReader, err := pdf.NewPdfReader(f)
if err != nil {
return err
}
isEncrypted, err := pdfReader.IsEncrypted()
if err != nil {
return err
}
// Try decrypting both with given password and an empty one if that fails.
if isEncrypted {
auth, err := pdfReader.Decrypt([]byte(""))
if err != nil {
return err
}
if !auth {
return errors.New("Unable to decrypt pdf with empty pass")
}
}
numPages, err := pdfReader.GetNumPages()
if err != nil {
return err
}
for i := 0; i < numPages; i++ {
pageNum := i + 1
page, err := pdfReader.GetPage(pageNum)
if err != nil {
return err
}
err = c.AddPage(page)
if err != nil {
return err
}
_ = c.RotateDeg(degrees)
}
err = c.WriteToFile(outputPath)
return err
}