PDFium for Web Assembly is working and has a web demo

Paulo Coutinho

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Jan 31, 2021, 5:07:20 AM1/31/21

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Hi,

It is working on my project here:

https://github.com/paulo-coutinho/pdfium-lib

And you can test on web here:

https://paulo-coutinho.github.io/pdfium-lib/

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Problems:

Some images are blue and i don't know why. Anyone understand why and can help?

Thanks.

Paulo Coutinho

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Jan 31, 2021, 6:45:21 AM1/31/21

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Hi,

I have fixed the color problem.

Daniel Hosseinian

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Feb 1, 2021, 3:32:51 PM2/1/21

to Paulo Coutinho, pdfium

Hi Paulo,

Neat project!

Glad to see you figured out the color problem. Were the images coming out blue because of the byte order? FPDF_REVERSE_BYTE_ORDER is helpful for switching from BGRA to RGBA when rendering to bitmaps.

Best,

Daniel

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Paulo Coutinho

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Feb 1, 2021, 3:44:06 PM2/1/21

to Daniel Hosseinian, pdfium

Wow nice man! Much more fast than my loop to change the bytes.

I see these options but don't see this exact option to revert it.

Thanks man.

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Atenciosamente,

Paulo Coutinho.

PRS - Soluções Inteligentes

Site: www.prsolucoes.com

Blog: www.pcoutinho.com
Skype: paulo.prsolucoes

Telefone: +55 21 99386-0010

Daniel Hosseinian

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Feb 1, 2021, 3:50:55 PM2/1/21

to Paulo Coutinho, pdfium

I'm not sure if I understood your concern exactly :)

You can use that flag in the `flag` parameter of methods like `FPDF_RenderPageBitmap()`. Here's an example where Chromium calls PDFium [1].

[1] https://source.chromium.org/chromium/chromium/src/+/master:pdf/pdfium/pdfium_page.cc;l=1519;drc=0b0661a20fa604ad87368572cd1e513b7e2abdd4

Paulo Coutinho

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Feb 1, 2021, 4:15:58 PM2/1/21

to Daniel Hosseinian, pdfium

Yes, I understand and i'm using it now.

I sad that I see this options/flags in the past but i don't remember about this option to revert bytes.

Im making now a better PDF modal in javascript to show the images without stretch the images.

Thanks.

Paulo Coutinho

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Feb 1, 2021, 8:06:14 PM2/1/21

to Daniel Hosseinian, pdfium

Hey man,

I have added a lot of functions now:

https://pdfviewer.github.io

or direct with PDF:

https://pdfviewer.github.io/?title=Demo%20PDF%20with%201MB&url=https://file-examples-com.github.io/uploads/2017/10/file-example_PDF_1MB.pdf

Im making a public viewer for any PDF.

Can you test?

I have tested with big/small PDF, with and without complex images, but only one PDF don't render images in my test. I will attach here. Can you help me understand why these images not render, but only the test?

Thanks.

sample-pdf-with-images.pdf

Daniel Hosseinian

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Feb 1, 2021, 8:28:38 PM2/1/21

to Paulo Coutinho, pdfium

Hi Paulo,

Again -- neat website! I'm glad to see developers put PDFium to great use!

Regarding your problem -- I'm not sure why the images are missing but I recommend that you try rendering the document with `pdfium_test` [1]. If it does render (which I think it should), then compare that code to yours. I took a quick look at your code [2] and I didn't see anything wrong with it. But then again, I didn't have time for a deep debug.

Please let me know if I can forward you to any other resources.

Cheers,

Danie;

[1] https://source.chromium.org/chromium/chromium/src/+/master:third_party/pdfium/samples/pdfium_test.cc

[2] https://github.com/paulo-coutinho/pdfium-lib/blob/master/sample/src/main.cpp

Paulo Coutinho

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Feb 1, 2021, 11:33:06 PM2/1/21

to Daniel Hosseinian, pdfium

Hi,

The source code is here:

https://github.com/paulo-coutinho/pdfium-lib/blob/master/extras/wasm/utils/custom.c

I have compared to your file (pdfium_test) and changed to version 3 only, but make no difference.

I see the render function too and don't see differences, only that you can enable v8, but i don't know if it is the problem.

I will test pdfium_test after.

Thanks anyway.

Daniel Hosseinian

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Feb 2, 2021, 12:18:05 PM2/2/21

to Paulo Coutinho, pdfium

Yup, give pdfium_test a try. By the way, pdfium_test has runtime flags for disabling V8, although I doubt that this PDF embeds any JavaScript.

Paulo Coutinho

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Feb 5, 2021, 2:18:57 PM2/5/21

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Hi,

After test with pdfium_test program, i have some conclusions:

- the page was exported with success (image is attached) with command:

./pdfium_test --png --pages=0 ~/Documents/PDF/sample-pdf-with-images.pdf

- there is no problem in render process of pdfium for desktop (ex: macos)

- something or is not compiled for wasm or some code are necessary to render it like in desktop program

I only need understand what is wrong now to finish it.

sample-pdf-with-images.pdf.0.png

sample-pdf-with-images.pdf

Paulo Coutinho

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Mar 26, 2021, 1:57:44 AM3/26/21

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Hi,

Can anyone help me on this?

Thanks.

Paulo Coutinho

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May 14, 2021, 3:27:10 PM5/14/21

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Hi,

We discovered some tips about the problem:

https://github.com/paulo-coutinho/pdfium-lib/issues/26

[attached]

It is related to "Jpeg Decoding".

Thanks for any help.

118282704-dda87700-b4ce-11eb-961a-df184c968787.png

Paulo Coutinho

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May 15, 2021, 2:42:16 PM5/15/21

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Hi,

Finally make it work.

The full issue history is here:

https://github.com/paulo-coutinho/pdfium-lib/issues/26

The repository updated is here:

https://github.com/paulo-coutinho/pdfium-lib

And the web demo is here:

https://pdfviewer.github.io/

Thanks.

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