Linearize PDFs in processing

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  • ¿Algo no está bien?
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Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
48/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
python
Área
backend

Línea de trabajo

The processing steps live under documentcloud/documents/processing/info_and_image, which the issue links as the place where PDFs are handled. Read that code to find where the PDF is written after processing, then check how pikepdf's Pdf.save is called there. Done means processed PDFs are saved in linearized form, with a test or manual check that the output is linearized. Whether the S3 bucket needs configuration for range requests is still open and should be settled first.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

processing

This would help loading large PDFs, building on this work in the viewer:

The one performance benefit of rendering PDF pages as images—instead of downloading the PDF and rendering it with PDF.js—is that very large files can be incrementally downloaded and rendered. In the majority of cases, downloading and rendering the PDF is faster and more performant than rendering an image for each page.

It appears to me that PDF.js supports partial rendering of linearized PDFs by default. In this demo, we can see in the network tab how each page is being independently fetched and rendered with 206 Partial Content responses. Linearizing a PDF requires additional steps during PDF creation (in Acrobat, there's a separate checkbox for "Fast Web View," which is a user-friendly name for linearization).

In a quick examination of DocumentCloud's processing pipeline, it doesn't appear to me that we perform linearization as a step in the process. While QPDF and pikepdf both support linearization, it's an opt-in feature that's disabled by default. It's unclear whether we need any special configuration to the S3 bucket to support partial requests, or if HTTP Range Requests are supported by default.

Lenguaje dominante
Python
Estrellas
55
Forks
10
Merge medio
1 d 13 h
PR fusionados (30 d)
22

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