Filters and Image Processing

Apply Image Filters

ScanbotSDK.applyImageFilters({ imageFileUri: string, filters: ParametricFilter[] })

Applies filters to an image. As input, a file URI of the image must be passed. The output image will be a new file. The input image file will not be modified.

Apply Image Filters usage example

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See full example on GitHub

Parameters

• imageFileUri - file URI of the image to rotate
• filters - array of ParametricFilter

Returns

Apply Image Filter Result

Apply Image Filters on Page

ScanbotSDK.applyImageFiltersOnPage({ page: Page, filters: ParametricFilter[] })

Applies an image filter to the hi-res document image of a Page (documentImageFileUri) and refreshes the corresponding preview image (documentPreviewImageFileUri). The original, uncropped image of a Page (originalImageFileUri) will not be modified.

Apply Image Filters on Page usage example

loading...

See full example on GitHub

Parameters

• imageFileUri - file URI of the image to rotate
• filters - array of ParametricFilter

Returns

Apply Image Filter on Page Result

Supported Image Filters

• ColorDocumentFilter
• ScanbotBinarizationFilter
• CustomBinarizationFilter
• BrightnessFilter
• ContrastFilter
• GrayscaleFilter
• WhiteBlackPointFilter
• LegacyFilter

Page Processing

All SDK components (UI and non-UI) which generate or modify scanned documents use the notion of a Page as a data model.

A Page object represents a scanned or imported document page.

Pages are stored in an internal page file storage, where the pageId serves as a name prefix for the stored image files. Operations that modify pages work in-place. That is, for example, rotatePage() overwrites the page's image files with their rotated versions. This behavior differs from the behavior of raw image functions like rotateImage() which always create a new file. All URI properties of a page have a ?minihash= query parameter appended to them with the hash of a portion of the image file. Different images will almost always have a different hash and therefore a different URI, which will force the WebView to reload the page's images when changed.

caution

Some file system operations require decoding of the URI before utilization. URI strings are ENCODED by default.

Persistence of Page Objects

Scanbot SDK does not persist page objects, only the image files (.jpg or .png). The management of page objects and the persistence of the page metadata is left to the app. Depending on the use case, it may be necessary to persist the data of the page objects in the app (e.g. as JSON in a local SQLite database). If this is the case, the following must be considered.

The Page objects contain absolute paths to the image files:

{
  "pageId": "60426F47-4119-48F8-ADA9-F7E60D583CB4",
  "documentPreviewImageFileUri": "file:///var/mobile/Containers/Data/Application/54286F82-A8F7-4850-A684-8D3487726A4D/Library/Application%20Support/net.doo.ScanbotSDK/SBSDK_ImageStorage_Default/PageFileStorage/JPEG/documents/60426F47-4119-48F8-ADA9-F7E60D583CB4_preview.jpg?minihash=a236a8ba5510cd0f4e88bd2045f52c4e",
  "originalImageFileUri": "file:///var/mobile/Containers/Data/Application/54286F82-A8F7-4850-A684-8D3487726A4D/Library/Application%20Support/net.doo.ScanbotSDK/SBSDK_ImageStorage_Default/PageFileStorage/JPEG/originals/60426F47-4119-48F8-ADA9-F7E60D583CB4.jpg?minihash=4e9f0446421343eaaa1e415fdb446a12",
  "originalPreviewImageFileUri": "file:///var/mobile/Containers/Data/Application/54286F82-A8F7-4850-A684-8D3487726A4D/Library/Application%20Support/net.doo.ScanbotSDK/SBSDK_ImageStorage_Default/PageFileStorage/JPEG/originals/60426F47-4119-48F8-ADA9-F7E60D583CB4_preview.jpg?minihash=da888cd42db07e52b15a6ada29a37b63",
  "documentImageFileUri": "file:///var/mobile/Containers/Data/Application/54286F82-A8F7-4850-A684-8D3487726A4D/Library/Application%20Support/net.doo.ScanbotSDK/SBSDK_ImageStorage_Default/PageFileStorage/JPEG/documents/60426F47-4119-48F8-ADA9-F7E60D583CB4.jpg?minihash=f9aab62cc37fec555abe94c83406a1b3",
  ...
}

The page image files are stored in corresponding storage locations - also see the Storage section. By default, the Scanbot SDK Android uses the internal files directory of the app, whereas the Scanbot SDK iOS uses the "Application Support" folder. Those storage folders are secure and are not affected by an app update.

However, on iOS, the absolute file path of the "Application Support" folder is not reliable. For each fresh install of an app, a new UUID is generated, in the following format: /var/mobile/Containers/Data/Application/{UUID}. That is where application data is stored. When updating the app, the uuid may change. For example:

Before an app update:

file:///var/mobile/Containers/Data/Application/54286F82-A8F7-4850-A684-8D3487726A4D/Library/Application%20Support/net.doo.ScanbotSDK/SBSDK_ImageStorage_Default/PageFileStorage/JPEG/documents/60426F47-4119-48F8-ADA9-F7E60D583CB4.jpg

After the app update:

file:///var/mobile/Containers/Data/Application/C9181555-252A-4665-892F-793008ED0EDD/Library/Application%20Support/net.doo.ScanbotSDK/SBSDK_ImageStorage_Default/PageFileStorage/JPEG/documents/60426F47-4119-48F8-ADA9-F7E60D583CB4.jpg

Please note that the actual image files are still there, only the absolute file paths change.

To get the new absolute paths, please use API method refreshImageUris({pages: Page []}) to refresh all image file URIs from affected pages:

import { ScanbotSDK } from 'capacitor-plugin-scanbot-sdk';

// Always make sure you have a valid license on runtime via ScanbotSDK.getLicenseInfo()
if (!(await this.isLicenseValid())) {
    return;
}

const result = await ScanbotSDK.refreshImageUris({pages: loadedPages});
const refreshedPages = result.pages;

It is highly recommended using this method whenever you have to (re-)load JSON Page objects from the database of your app, regardless of whether there was an app update or not.

Page Operations

Create Page

ScanbotSDK.createPage(args:{ imageUri: string })

Creates a Page object from an image file (presumably the original image of an uncropped document) and returns the created page object.

As the page has not been cropped yet, the documentImageFileUri and documentPreviewImageFileUri properties will be empty.

Set Document Image

ScanbotSDK.setDocumentImage(args:{ page: Page, imageFileUri: string })

Replaces the document image of a page. The passed image file will be copied into the internal page file storage.

Returns the updated page.

Remove Page

ScanbotSDK.removePage(args:{ page: Page })

Removes a page with all its files (original image, document image, thumbnails, filtered images, etc) from the internal file storage.

This method does not remove any export files (PDF, TIFF) which were generated based on this page object.

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