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main.go
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main.go
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// seehuhn.de/go/pdf - a library for reading and writing PDF files
// Copyright (C) 2024 Jochen Voss <voss@seehuhn.de>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package main
import (
"bytes"
"io"
"log"
"seehuhn.de/go/pdf"
"seehuhn.de/go/pdf/document"
"seehuhn.de/go/pdf/font/type1"
"seehuhn.de/go/pdf/graphics"
"seehuhn.de/go/pdf/graphics/form"
"seehuhn.de/go/pdf/graphics/matrix"
"seehuhn.de/go/pdf/pagetree"
)
func main() {
err := run()
if err != nil {
log.Fatal(err)
}
}
func run() error {
paper := document.A4
page, err := document.CreateSinglePage("test.pdf", paper, pdf.V1_7, nil)
if err != nil {
return err
}
B, err := type1.TimesBold.Embed(page.Out, nil)
if err != nil {
return err
}
F, err := type1.TimesRoman.Embed(page.Out, nil)
if err != nil {
return err
}
figure, bbox, err := LoadFigure("fig.pdf", page.Out)
if err != nil {
return err
}
width := bbox.Dx()
height := bbox.Dy()
base := paper.URy - 72 - height
left := paper.LLx + 0.5*(paper.Dx()-width)
page.PushGraphicsState()
page.Transform(matrix.Translate(left-bbox.LLx, base-bbox.LLy))
page.DrawXObject(figure)
page.PopGraphicsState()
base -= 12
page.TextStart()
page.TextFirstLine(72, base)
page.TextSetFont(B, 10)
page.TextShow("Figure 1. ")
page.TextSetFont(F, 10)
page.TextShow("A grid of pair scatter plots for R's built-in iris dataset. The plot illustrates the joint distribution")
page.TextSecondLine(0, -12)
page.TextShow("of sepal length, sepal width, petal length, and petal width for three species of iris.")
page.TextEnd()
err = page.Close()
if err != nil {
return err
}
return nil
}
func LoadFigure(fname string, w pdf.Putter) (*graphics.XObject, *pdf.Rectangle, error) {
r, err := pdf.Open(fname, nil)
if err != nil {
return nil, nil, err
}
dict, err := pagetree.GetPage(r, 0)
if err != nil {
return nil, nil, err
}
cropBox := dict["CropBox"]
if cropBox == nil {
cropBox = dict["MediaBox"]
}
bbox, err := pdf.GetRectangle(r, cropBox)
if err != nil {
return nil, nil, err
}
copier := NewCopier(w, r)
origResources, err := pdf.GetDict(r, dict["Resources"])
if err != nil {
return nil, nil, err
}
resourceObj, err := copier.Copy(origResources)
resourceDict := resourceObj.(pdf.Dict)
resources := &pdf.Resources{}
err = pdf.DecodeDict(nil, resources, resourceDict)
if err != nil {
return nil, nil, err
}
body := &bytes.Buffer{}
contents, err := pdf.Resolve(r, dict["Contents"])
switch x := contents.(type) {
case *pdf.Stream:
stm, err := pdf.DecodeStream(r, x, 0)
if err != nil {
return nil, nil, err
}
_, err = io.Copy(body, stm)
if err != nil {
return nil, nil, err
}
case pdf.Array:
for _, ref := range x {
obj, err := pdf.GetStream(r, ref)
if err != nil {
return nil, nil, err
}
stm, err := pdf.DecodeStream(r, obj, 0)
if err != nil {
return nil, nil, err
}
_, err = io.Copy(body, stm)
if err != nil {
return nil, nil, err
}
}
}
err = r.Close()
if err != nil {
return nil, nil, err
}
figure := &form.FormProperties{
BBox: bbox,
}
obj, err := form.Raw(w, figure, body.Bytes(), resources)
if err != nil {
return nil, nil, err
}
return obj, bbox, nil
}
type copier struct {
trans map[pdf.Reference]pdf.Reference
w pdf.Putter
r pdf.Getter
}
func NewCopier(w pdf.Putter, r pdf.Getter) *copier {
res := &copier{
trans: make(map[pdf.Reference]pdf.Reference),
w: w,
r: r,
}
return res
}
func (w *copier) Copy(obj pdf.Object) (pdf.Object, error) {
switch x := obj.(type) {
case pdf.Dict:
res := pdf.Dict{}
for key, val := range x {
repl, err := w.Copy(val)
if err != nil {
return nil, err
}
res[key] = repl
}
return res, nil
case pdf.Array:
var res pdf.Array
for _, val := range x {
repl, err := w.Copy(val)
if err != nil {
return nil, err
}
res = append(res, repl)
}
return res, nil
case *pdf.Stream:
res := &pdf.Stream{
Dict: make(pdf.Dict),
R: x.R,
}
for key, val := range x.Dict {
repl, err := w.Copy(val)
if err != nil {
return nil, err
}
res.Dict[key] = repl
}
return res, nil
case pdf.Reference:
other, ok := w.trans[x]
if ok {
return other, nil
}
other = w.w.Alloc()
w.trans[x] = other
val, err := pdf.Resolve(w.r, x)
if err != nil {
return nil, err
}
trans, err := w.Copy(val)
if err != nil {
return nil, err
}
err = w.w.Put(other, trans)
if err != nil {
return nil, err
}
return other, nil
}
return obj, nil
}