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booklet.go
60 lines (54 loc) · 1.75 KB
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booklet.go
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package pdf
import (
"bytes"
"context"
"fmt"
"github.com/pdfcpu/pdfcpu/pkg/api"
"github.com/pdfcpu/pdfcpu/pkg/pdfcpu"
"go.opentelemetry.io/otel"
)
var bookletTracer = otel.GetTracerProvider().Tracer("booklet")
func makePrintableBooklet(ctx context.Context, pages *bytes.Buffer) (printablePages bytes.Buffer, err error) {
_, span := bookletTracer.Start(ctx, "makePrintableBooklet")
defer span.End()
config := pdfcpu.NewDefaultConfiguration()
pageCount, _ := api.PageCount(bytes.NewReader(pages.Bytes()), config)
// Add empty pages to make leaflet to be printable
if pageCount%4 > 0 {
for i := 0; i < (4 - pageCount%4); i++ {
printablePages.Reset()
err := api.InsertPages(bytes.NewReader(pages.Bytes()), &printablePages, []string{fmt.Sprintf("%d", pageCount)}, false, config)
if err != nil {
fmt.Printf("Error at InsertPages: %v\n", err)
}
*pages = printablePages
}
}
pageCount, _ = api.PageCount(bytes.NewReader(pages.Bytes()), config)
printablePages.Reset()
err = api.Collect(bytes.NewReader(pages.Bytes()), &printablePages, calculatePageOrder(pageCount), config)
if err != nil {
fmt.Printf("Error at Collect: %v\n", err)
}
*pages = printablePages
printablePages.Reset()
nupConfig, err := pdfcpu.PDFGridConfig(1, 2, "")
if err != nil {
fmt.Printf("Error at PDFGridConfig: %v\n", err)
}
err = api.NUp(bytes.NewReader(pages.Bytes()), &printablePages, nil, nil, nupConfig, config)
if err != nil {
fmt.Printf("Error at NUp: %v\n", err)
}
return
}
func calculatePageOrder(pageCount int) (pageOrder []string) {
for i := 0; i < pageCount/2; i++ {
if i%2 == 0 {
pageOrder = append(pageOrder, fmt.Sprint(pageCount-i), fmt.Sprint(i+1))
} else {
pageOrder = append(pageOrder, fmt.Sprint(i+1), fmt.Sprint(pageCount-i))
}
}
return
}