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WebTwain Buffer Manage

Methods

       
ClearImageTags() RenameTag() RemoveTag() GetTagList()
FilterImagesByTag() ClearFilter() SetDefaultTag() TagImages()
GetImageBitDepth() GetImageSize() GetImageSizeWithSpecifiedType() GetSelectedImagesSize()
GetImageHeight() GetImageWidth() GetImagePartURL() GetImageURL()
GetImageXResolution() GetImageYResolution() GetSkewAngle() GetSkewAngleEx()
ImageIDToIndex() IndexToImageID() IsBlankImage() IsBlankImageExpress()
SelectAllImages() MoveImage() SwitchImage() RemoveImage()
RemoveAllImages() RemoveAllSelectedImages() SelectImages()  

Properties

       
BlankImageCurrentStdDev BlankImageMaxStdDev BlankImageThreshold BufferMemoryLimit
CurrentImageIndexInBuffer HowManyImagesInBuffer IfAllowLocalCache SelectedImagesIndices
MaxImagesInBuffer      

Events

       
OnBufferChanged OnBitmapChanged OnIndexChangeDragDropDone OnTopImageInTheViewChanged

IndexToImageID

Syntax

/**

* Return the imageId of an image specified by the index.
* @param index The index of the image.

*/
IndexToImageID(index: number): number;

ImageIDToIndex

Syntax

/**
 * Return the index of an image specified by the imageId.
 * @param imageId The imageId of the image.
 */
ImageIDToIndex(imageId: number): number;

Usage notes

An imageId is unique and won’t change as long as the Dynamsoft Service process is running. It’s a better way to keep track of an image than the index which changes easily.


RenameTag

Syntax

/**
 * Rename a tag.
 * @param oldName Specify the tag to change.
 * @param newName Specify the new tag name.
 */
RenameTag(oldName:string, newName:string): boolean;

RemoveTag

Syntax

/**
 * Remove the specified tag from one or more images(if not specified, remove from all). 
 * @param tagName Specify the new tag name.
 * @param indices Specify the index.
 */
RemoveTag(tagName: string, indices?: number[]):boolean 

Usage Notes If the index is null, it will remove the tag you specified. If the index is not null, it will remove the specified tag on the image you selected.


GetTagList

Syntax

/**
 * Return the status of all current tags. 
 */
GetTagList():Json 

Json 
[ 
   { 
        name: TagA,  
         imageIds:  
   }, 
   { 
        name: TagB,  
         imageIds:[239514082, 239514083] 
   }, 
] 
 

ClearImageTags

Syntax

/**
 * Remove all tags from the specified image.
 * @param index Specify the image.
 */
ClearImageTags(index: number): boolean;

FilterImagesByTag

Syntax

/**
 * Filter images by the specified tag.
 * @param tag The tag used as the filter. If nothing or an empty string is used, the filter is cleared.
 */
FilterImagesByTag(tag: string): boolean;

ClearFilter

Syntax

/**
 * Stop filtering images by tag.
 */
ClearFilter(): boolean;

SetDefaultTag

Syntax

/**
 * Set a default tag for newlay acquired images.
 * @param tag Specifies the tag.
 */
SetDefaultTag(tag: string): boolean;

TagImages

Syntax

/**
 * Add a tag to specified images.
 * @param indices Specifies images to be tagged.
 * @param tag Specify the tag.
 */
TagImages(indices: number[], tag: string): boolean;

GetImageBitDepth

Syntax

/**
 * Return the pixel bit depth of the specified image.
 * @param index Specify the image.
 */
GetImageBitDepth(index: number): number;

GetImageHeight

Syntax

/**
 * Return the height (in pixels) of the specified image.
 * @param index Specify the image.
 */
GetImageHeight(index: number): number;

GetImageWidth

Syntax

/**
 * Return the width (in pixels) of the specified image.
 * @param index Specify the image.
 */
GetImageWidth(index: number): number;

GetImageXResolution

Syntax

/**
 * Return the horizontal resolution of the specified image.
 * @param index Specify the image.
 */
GetImageXResolution(index: number): number;

GetImageYResolution

Syntax

/**
 * Return the vertical resolution of the specified image.
 * @param index Specify the image.
 */
GetImageYResolution(index: number): number;

GetSkewAngle

Syntax

/**
 * Return the skew angle of the specified image.
 * @param index Specify the image.
 * @param successCallback A callback function that is executed if the request succeeds.
 * @param failureCallback A callback function that is executed if the request fails.
 * @argument angle The skew angle.
 * @argument errorCode The error code.
 * @argument errorString The error string.
 */
GetSkewAngle(
    index: number,
    successCallback?: (
        angle: number) => void,
    failureCallback?: (
        errorCode: number, 
        errorString: string) => void
): number | void;

GetSkewAngleEx

Syntax

/**
 * Return the skew angle of the specified rectangle on the specified image.
 * @param index Specify the image.
 * @param left The x-coordinate of the upper-left corner of the rectangle.
 * @param top The y-coordinate of the upper-left corner of the rectangle.
 * @param right The x-coordinate of the lower-right corner of the rectangle.
 * @param bottom The y-coordinate of the lower-right corner of the rectangle.
 * @param successCallback A callback function that is executed if the request succeeds.
 * @param failureCallback A callback function that is executed if the request fails.
 * @argument angle The skew angle.
 * @argument errorCode The error code.
 * @argument errorString The error string.
 */
GetSkewAngleEx(
    index: number,
    left: number,
    top: number,
    right: number,
    bottom: number,
    successCallback?: (
        angle: number) => void,
    failureCallback?: (
        errorCode: number, 
        errorString: string) => void
): number | void;

Usage notes

After you get the skew angle of an image, you can rotate it with the method Rotate to perform deskewing.


GetImageSize

Syntax

/**
 * Calculate the size in bytes of the specified image assuming it's resized to the given dimensions.
 * @param index Specify the image.
 * @param width Specify the width.
 * @param height Specify the height.
 */ 
GetImageSize(index: number, width: number, height: number): number;

GetImageSizeWithSpecifiedType

Syntax

/**
 * Calculate the size in bytes of the specified image assuming an expected file type.
 * @param index Specify the image.
 * @param type Sepcify the expected file type.
 */ 
GetImageSizeWithSpecifiedType(index: number, type: Dynamsoft.DWT.EnumDWT_ImageType | number): number;

GetSelectedImagesSize

Syntax

/**
 * Calculate the size in bytes of all selected images assuming an expected file type.
 * @param type Sepcify the expected file type.
 */
GetSelectedImagesSize(type: Dynamsoft.DWT.EnumDWT_ImageType | number): number;

Usage notes

If the calculation fails, -1 is returned.


GetImagePartURL

Syntax

/**
 * Return the internal URL of the specified image. 
 * @param index Specify the image.
 * @param width The width of the image (>150).
 * @param height The height of the image (>150).
 */
GetImagePartURL(index: number, width?: number, height?: number): string;

Usage notes

If width and height are not specified, you get the original image, otherwise you get the image with specified width or height while keeping the same aspect ratio. The returned string is like this ‘dwt://dwt_trial_13000404/img?id=306159652&index=0&t=1502184632022’.


GetImageURL

Syntax

/**
 * Return the direct URL of the specified image. 
 * @param index Specify the image.
 * @param width The width of the image (>150).
 * @param height The height of the image (>150).
 */
GetImageURL(index: number, width?: number, height?: number): string;

Usage notes

If width or height is set to -1, you get the original image, otherwise you get the image with specified width or height while keeping the same aspect ratio.


SelectAllImages

Syntax

/**
 * Select all images and return the indices. Viewer will be scrolled to the last image.
 */
SelectAllImages(): number[];

SelectImages

Syntax


/**
 * Select the specified images.
 * @param indices Specify one or multiple images.
 */
SelectImages(indices: number[]): boolean;

MoveImage

Syntax

/**
 * Change the position of an image in the buffer.
 * @param from Specify the original position by index.
 * @param to Specify the target position by index.
 */
MoveImage(from: number, to: number): boolean;

SwitchImage

Syntax

/**
 * Exchange the positions of two images.
 * @param index1 Specify the 1st image.
 * @param index2 Specify the 2nd image.
 */
SwitchImage(index1: number, index2: number): boolean;

RemoveImage

Syntax

/**

* Remove the specified image.
* @param index Specify the image.

*/
RemoveImage(index: number): boolean;

RemoveAllImages

Syntax

/**
 * Remove all images.
 */
RemoveAllImages(): boolean;

RemoveAllSelectedImages

Syntax

/**
 * Remove all selected images.
 */
RemoveAllSelectedImages(): boolean;

CurrentImageIndexInBuffer

Syntax

/**
 * Return the index of the current image in the buffer or 
 * Set the image specified by index as the current image.
 */
CurrentImageIndexInBuffer: number;

HowManyImagesInBuffer

Syntax

/**
 * Return how many images are held in the buffer
 */
readonly HowManyImagesInBuffer: number;

MaxImagesInBuffer

Syntax

/**
 * Return or set how many images can be held in the buffer.
 */ 
MaxImagesInBuffer: number;

Usage notes

When acquiring images and the number of images goes beyond the value set to MaxImagesInBuffer , new images will replace old images starting from the 1st one.


SelectedImagesIndices

Syntax

/**
 * Return the indices of the selected images.
 */
readonly SelectedImagesIndices: number[];

SelectionRectAspectRatio

Syntax

/**
 * Specify a aspect ratio to be used when selecting a rectangle on an image.
 */
SelectionRectAspectRatio: number; 

BlankImageCurrentStdDev

Syntax

/**
 * Return the deviation of the pixels in the current image.
 */
readonly BlankImageCurrentStdDev: number;

BlankImageMaxStdDev

Syntax

/**
 * Return or set the maximum deviation of the pixels in an image which is used to determine whether the image is blank.
 */
BlankImageMaxStdDev: number;

BlankImageThreshold

Syntax

/**
 * Returns or sets the dividing line between black and white.
 */
BlankImageThreshold: number;

Usage notes

[0, 255] is the interval of allowed values, inclusive. The default value is 128. This property is only valid after IsBlankImageExpress is called.


BufferMemoryLimit

Syntax

/**
 * Return or set how much physical memory is allowed for storing images currently 
 * loaded in Dynamic Web TWAIN. Once the limit is reached, images will be cached on the hard disk.
 */
BufferMemoryLimit: number;

Usage notes

Set this property only when you have a very small physical memory (< 2GB) or a very big one (>4GB). The more memory is allowed, the better the performance will be. The default value is set to 800 (MB), anything beyond 800MB gets compressed, encrypted and cached on the local disk.

All cached data is encrypted and can only be read by Dynamic Web TWAIN and it will be destroyed when it is no longer used.


IsBlankImage

Syntax

/** 
 * Check whether the specified image is blank.
 * @param index Specify the image.
 */ 
IsBlankImage(index: number): boolean;

IsBlankImageExpress

Syntax

/** 
 * Check whether the specified image is blank.
 * @param index Specify the image.
 */
IsBlankImageExpress(index: number): boolean;

Usage notes

IsBlankImage is more accurate than IsBlankImageExpress but it works slower.

BlankImageCurrentStdDev should be read after either IsBlankImage() or IsBlankImageExpress .

If you believe an image should be blank but IsBlankImage() or IsBlankImageExpress is returning false , you can read BlankImageCurrentStdDev for that image and then set a bigger value to BlankImageMaxStdDev .

Both BlankImageCurrentStdDev and BlankImageMaxStdDev range from 0 to 100.


IfAllowLocalCache

Syntax

/**
 * Return or set whether the feature of disk caching is enabled.
 */
IfAllowLocalCache: boolean;

OnBufferChanged

Syntax

/**
 * An enhanced callback triggered when a change occurs in the buffer.
 * @argument bufferChangeInfo Details about the buffer change.
 */
RegisterEvent('OnBufferChanged',
    function (bufferChangeInfo: BufferChangeInfo) {}
): boolean;

interface BufferChangeInfo {
    /**
     * Action type includes 'add', 'remove', 'modify', 'shift' and 'filter'
     */
    action: string;
    /**
     * The image id (not the index) of the current page.
     */
    currentId: number;
    /**
     * All image ids.
     */
    imageIds: number[];
    /**
     * All selected image ids.
     */
    selectedIds: number[];
}

Usage notes

Action types include

  • add: New pages are added to the buffer.
  • remove: The existing pages are removed.
  • modify: The existing pages are modified.
  • shift: The existing pages are reordered.
  • filter: The existing pages are filtered by a tag.

OnBitmapChanged

Syntax

/**
 * A built-in callback triggered when a change occurs in the buffer.
 * @argument indexString A string of the changed index(indices).
 * @argument type Operation type.
 * @argument index Index of the current image.
 */
RegisterEvent('OnBitmapChanged',
    function (indexString: string,
        type: number,
        index: number
    ) {}
): boolean; 

Usage notes

Operation types include

  • new image(s) were added at the tail
  • new image(s) were inserted before the current index
  • image(s) are deleted
  • image(s) are modified
  • indices of images changed

OnTopImageInTheViewChanged

Syntax

/**
 * A built-in callback triggered when the top index currently displayed in the viewer changes.
 * @argument index Index of the current image.
 */
RegisterEvent('OnTopImageInTheViewChanged',
    function (index: number) {}
): boolean; 

Usage notes

This API does not work if the view mode of the viewer is set to -1 by -1.


OnIndexChangeDragDropDone

Syntax

/**
 * A built-in callback triggered when images in the buffer are dragged to new positions.
 * @argument indexPairs The list of index changes.
 */
RegisterEvent('OnIndexChangeDragDropDone',
    function (indexPairs: Pair[]) {}
): boolean; 

Pair: [from: number, to: number];

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