anyone use pdfium from golang?

[Ryan Pendergast]

Wondering if anyone has experience using pdfium from go.  I know you can compile go programs to use c[++] libs via cgo, however I haven't used c[++] in forever and can't figure out how to write a go program to utilize the pdfium lib.

ninja -C out/build pdfium

produces a obj/libpdfium.a file.  Does anyone have experience with this, that can give me a small example of how I would include libpdfium.a into my go program and call a function?  An example using cgo to compile said program would also be very helpful.

My end goal is to fill out FDF fields in a PDF using go.

thanks in advance

[Phil Richards]

Here's a sample - it provides a pdfium.Context Go type (which has a Close method) and a NewContext ctor. NewContext calls FPDF_InitLibrary and Context.Close calls FPDF_DestroyLibrary. 

package pdfium

/*

#cgo CXXFLAGS: -I${SRCDIR}/include -std=c++11

#cgo CFLAGS: -I${SRCDIR}/include

#cgo LDFLAGS: -L${SRCDIR}/libs -lpdfium

#include <fpdfview.h>

#include <fpdf_edit.h>

#include <fpdf_doc.h>

#include <stdlib.h>

*/

import "C"

import (

"github.com/pkg/errors"

"sync"

)

var mut sync.Mutex

type Context struct{}

func NewContext() *Context {

mut.Lock()

defer mut.Unlock()

C.FPDF_InitLibrary()

return &Context{}

}

func (c *Context) Close() error {

mut.Lock()

defer mut.Unlock()

C.FPDF_DestroyLibrary()

return nil

}

//func (c *Context) NewDoc() *Doc {

// mut.Lock()

// defer mut.Unlock()

//

// return &Doc{

// cdoc: C.FPDF_CreateNewDocument(),

// }

//}

The lines above 'import "C"' tell the go tool where to look for headers and library files; 'SRCDIR' refers to the directory that contains the above file. Hopefully that should get you started :)

[Jonas Brunsgaard]

I just started working on it.

https://github.com/brunsgaard/go-pdfium-render/

[Rodrigo Aliste]

We use it for rendering page bitmaps into PNG and for metadata extraction. We basically implemented what Jonas already shared, but we took a subprocess approach as we needed random document access and high concurrency (we use it as part of an RPC system).

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[Vignan E-Giants]

The one provided by Jonas is a great starting point to parse pdfs into images.  Wondering if anyone here can provide something similar with FPDF_SaveAsCopy functionality in Go.

On Tuesday, October 23, 2018 at 5:51:40 PM UTC-4, Rodrigo Aliste wrote:

We use it for rendering page bitmaps into PNG and for metadata extraction. We basically implemented what Jonas already shared, but we took a subprocess approach as we needed random document access and high concurrency (we use it as part of an RPC system).

El mar., 23 oct. 2018 a las 18:28, Jonas Brunsgaard (<jonas.b...@gmail.com>) escribió:

I just started working on it.

https://github.com/brunsgaard/go-pdfium-render/



On Thursday, 26 April 2018 22:31:14 UTC+2, Ryan Pendergast wrote:

Wondering if anyone has experience using pdfium from go.  I know you can compile go programs to use c[++] libs via cgo, however I haven't used c[++] in forever and can't figure out how to write a go program to utilize the pdfium lib.

ninja -C out/build pdfium

produces a obj/libpdfium.a file.  Does anyone have experience with this, that can give me a small example of how I would include libpdfium.a into my go program and call a function?  An example using cgo to compile said program would also be very helpful.

My end goal is to fill out FDF fields in a PDF using go.

thanks in advance

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[Jeroen Bobbeldijk]

Anyone passing by might want to check this out: https://github.com/klippa-app/go-pdfium

It's a Go implementation of PDFium that handles all the cgo stuff for you, and it also allows you to use it in the same process or multi-threaded using a sub-process approach.

I'm working on implementing the full API, but the most important stuff is in there.

FPDF_SaveAsCopy is also implemented here, as is FPDF_CreateNewDocument and FPDF_ImportPages, so you can also use it to merge/split pages, which is probably what the person above me wants to do.