Straightening documents with the Linux Document Scanner

The Document Enhancer can straighten scanned documents by removing paper deformations such as creases, curl, folds, and crinkles, and correcting perspective distortion.

It supports two straightening modes:

Mode	Description
NONE	Crops the document based on estimated perspective distortion. Very fast.
STRAIGHTEN	Removes paper deformations in addition to perspective correction.

Straightening an image

You can also straighten an image directly using the DocumentEnhancer API, providing full control over the enhancement process.

Python

straightening document

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See full example on GitHub

Java

straightening document

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NodeJS

straightening document

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C

straightening document

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Configuration options

The DocumentStraighteningParameters class provides the following options:

Python

Parameter	Type	Default	Description
straightening_mode	DocumentStraighteningMode	DocumentStraighteningMode.STRAIGHTEN	The type of straightening to apply.
aspect_ratios	list[AspectRatio]	Empty	Expected aspect ratios for the document. The closest matching ratio from the list is used.

Java

Parameter	Type	Default	Description
straighteningMode	DocumentStraighteningMode	DocumentStraighteningMode.STRAIGHTEN	The type of straightening to apply.
aspectRatios	List<AspectRatio>	Empty	Expected aspect ratios for the document. The closest matching ratio from the list is used.

NodeJS

Parameter	Type	Default	Description
straighteningMode	DocumentStraighteningMode	"STRAIGHTEN"	The type of straightening to apply.
aspectRatios	AspectRatio[]	Empty	Expected aspect ratios for the document. The closest matching ratio from the list is used.

C

Parameter	Type	Default	Description
straighteningMode	scanbotsdk_document_straightening_mode_t	SCANBOTSDK_DOCUMENT_STRAIGHTENING_MODE_STRAIGHTEN	The type of straightening to apply.
aspect_ratios	scanbotsdk_aspect_ratio_t**	Empty	Expected aspect ratios for the document. The closest matching ratio from the list is used.

Aspect ratios

By default, the aspect ratio of the straightened document is automatically determined from the detected document corners. If the document is significantly deformed, the estimated aspect ratio may be inaccurate.

Python

In such cases, you can provide a list of expected aspect ratios using params.aspect_ratios to improve accuracy. Note that if you want to support both portrait and landscape orientations for a given paper format, provide both aspect ratios, for example AspectRatio(width=21.0, height=29.7) and AspectRatio(width=29.7, height=21.0) for A4.

Java

In such cases, you can provide a list of expected aspect ratios using params.setAspectRatios(...) to improve accuracy. Note that if you want to support both portrait and landscape orientations for a given paper format, provide both aspect ratios, for example new AspectRatio(21.0, 29.7) and new AspectRatio(29.7, 21.0) for A4.

NodeJS

In such cases, you can provide a list of expected aspect ratios using params.aspectRatios to improve accuracy. Note that if you want to support both portrait and landscape orientations for a given paper format, provide both aspect ratios, for example new AspectRatio({ width: 21.0, height: 29.7 }) and new AspectRatio({ width: 29.7, height: 21.0 }) for A4.

C

In such cases, you can provide a list of expected aspect ratios when creating scanbotsdk_document_straightening_parameters_t to improve accuracy. Note that if you want to support both portrait and landscape orientations for a given paper format, provide both aspect ratios, for example by creating scanbotsdk_aspect_ratio_t values for 21.0 x 29.7 and 29.7 x 21.0 for A4.

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Scanbot SDK is part of the Apryse SDK product family

A mobile scan is just the start. With Apryse SDKs, you can expand mobile workflows into full cross‑platform document processing. Whether you need to edit PDFs, add secure digital signatures, or use a fast, customizable document viewer and editor, Apryse gives you the tools to build powerful features quickly.

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