PDFTron WebViewer

Class: Filter

Core.PDFNet. Filter

new Filter()

Provides a generic view of a sequence of bytes. A Filter is the abstract base class of all filters. A filter is an abstraction of a sequence of bytes, such as a file, an input/output device, an inter-process communication pipe, or a TCP/IP socket. The Filter class and its derived classes provide a generic view of these different types of input and output, isolating the programmer from the specific details of the operating system and the underlying devices. Besides providing access to input/output sources Filters can be also to transform the data (e.g. to compress the data stream, to normalize the image data, to encrypt data, etc). Filters can also be attached to each other to form pipelines. For example, a filter used to open an image data file can be attached to a filter that decompresses the data, which is attached to another filter that will normalize the image data. Depending on the underlying data source or repository, filters might support only some of these capabilities. An application can query a stream for its capabilities by using the IsInputFilter() and CanSeek() properties. Note: To read or write data to a filter, a user will typically use FilterReader/FilterWriter class. instead of using Filter methods For example: 
StdFile file("my_stream.txt", StdFile::e_read_mode);
FilterReader reader(file);
while (reader.Read(..)) ...

Extends

Members

<static> ReferencePos

Type:
  • number
Properties:
Name Type Description
e_begin number
e_end number
e_cur number

<static> StdFileOpenMode

Type:
  • number
Properties:
Name Type Description
e_read_mode number
e_write_mode number
e_append_mode number

Methods

<static> createFlateEncode( [input_filter] [, compression_level] [, buf_sz])

Constructor for Flate encoder. FlateEncode filter can be used to compress any data stream using Flate (i.e. ZIP) compression method.
Parameters:
Name Type Argument Default Description
input_filter Core.PDFNet.Filter <optional>
 PDFNet.Filter("0") the input data stream
compression_level number <optional>
 -1 compression_level must be a number between 0 and 9: 1 gives best speed, 9 gives best compression, 0 gives no compression at all (the input data is simply copied a block at a time), -1 requests a default compromise between speed and compression (currently equivalent to level 6).
buf_sz number <optional>
 256 filter buffer size (in bytes).
Returns:
A promise that resolves to an object of type: "Filter" (generated documentation)
Type
Promise.<Core.PDFNet.Filter>

<static> createFromMemory(buf)

Parameters:
Name Type Description
buf ArrayBuffer | Int8Array | Uint8Array | Uint8ClampedArray A memory buffer containing the underlying data.
Returns:
A promise that resolves to a "Filter" created from the buffer
Type
Promise.<Core.PDFNet.Filter>

<static> createImage2RGB(img)

Parameters:
Name Type Description
img Core.PDFNet.Image
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createImage2RGBA(img, premultiply)

Parameters:
Name Type Description
img Core.PDFNet.Image
premultiply boolean
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createImage2RGBAFromElement(elem, premultiply)

Parameters:
Name Type Description
elem Core.PDFNet.Element
premultiply boolean
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createImage2RGBAFromObj(obj, premultiply)

Parameters:
Name Type Description
obj Core.PDFNet.Obj
premultiply boolean
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createImage2RGBFromElement(elem)

Parameters:
Name Type Description
elem Core.PDFNet.Element
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createImage2RGBFromObj(obj)

Parameters:
Name Type Description
obj Core.PDFNet.Obj
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createMemoryFilter(buf_sz, is_input)

Parameters:
Name Type Description
buf_sz number
is_input boolean
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

<static> createURLFilter(url [, options])

Parameters:
Name Type Argument Description
url string A url from which the data can be downloaded.
options object <optional>
 Additional options
Properties
Name Type Description
withCredentials boolean Whether to set the withCredentials property on the XMLHttpRequest
customHeaders object An object containing custom HTTP headers to be used when downloading the document
Returns:
A promise that resolves to a "Filter" created from the url
Type
Promise.<Core.PDFNet.Filter>

attachFilter(attach_filter)

Attaches a filter to the this filter. If this filter owns another filter it will be deleted. This filter then becomes the owner of the attached filter.
Parameters:
Name Type Description
attach_filter Core.PDFNet.Filter filter object to attach
Returns:
Type
Promise.<void>

begin()

Returns:
A promise that resolves to beginning of the buffer of Size() bytes that can be used to read or write data.
Type
Promise.<number>

canSeek()

Returns:
A promise that resolves to true if the stream supports seeking; otherwise, false. default is to return false.
Type
Promise.<boolean>

consume(num_bytes)

Moves the Begin() pointer num_bytes forward.
Parameters:
Name Type Description
num_bytes number number of bytes to consume. num_bytes must be less than or equal to Size().
Returns:
Type
Promise.<void>

count()

Returns:
A promise that resolves to the number of bytes consumed since opening the filter or the last Seek operation
Type
Promise.<number>

createASCII85Encode(line_width, buf_sz)

Parameters:
Name Type Description
line_width number
buf_sz number
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

createInputIterator()

Create Filter iterator. Filter iterator similar to a regular filter. However, there can be only one owner of the attached filter. Note: Derived classes should make sure that there is only one owner of the attached stream. Otherwise the attached stream may be deleted several times.
Returns:
A promise that resolves to an object of type: "PDFNet.Filter"
Type
Promise.<Core.PDFNet.Filter>

destroy()

Destructor
Inherited From:
Returns:
Type
Promise.<void>

flush()

Forces any data remaining in the buffer to be written to input or output filter.
Returns:
Type
Promise.<void>

flushAll()

Forces any data remaining in the filter chain to the source or destination.
Returns:
Type
Promise.<void>

getAttachedFilter()

Returns:
A promise that resolves to returns attached Filter or a NULL filter if no filter is attached.
Type
Promise.<Core.PDFNet.Filter>

getDecodeName()

Returns:
A promise that resolves to string representing the name of corresponding decode filter as it should appear in document (e.g. both ASCIIHexDecode and ASCIIHexEncode should return ASCIIHexDecode).
Type
Promise.<string>

getFilePath()

Returns:
A promise that resolves to the file path to the underlying file stream. Default implementation returns empty string.
Type
Promise.<string>

getName()

Returns:
A promise that resolves to descriptive name of the filter.
Type
Promise.<string>

getSourceFilter()

Returns:
A promise that resolves to returns the first filter in the chain (usually a file filter)
Type
Promise.<Core.PDFNet.Filter>

isInputFilter()

Returns:
A promise that resolves to boolean indicating whether this is an input filter.
Type
Promise.<boolean>

memoryFilterGetBuffer()

Note: MemoryFilter specific function.
Returns:
A promise that resolves to a pointer to the beginning of the buffer. Use method Count() to determine the number of bytes written to or read from MemoryFilter.
Type
Promise.<number>

memoryFilterReset()

Returns:
Type
Promise.<void>

memoryFilterSetAsInputFilter()

Note: MemoryFilter specific function used to change filter mode from output to input. The utility function is useful in cases when and output data buffer should be converted to an input stream. Note: The function has no effect on an input MemoryFilter.
Returns:
Type
Promise.<void>

releaseAttachedFilter()

Release the ownership of the attached filter. After the attached filter is released this filter points to NULL filter.
Returns:
A promise that resolves to Previously attached filter.
Type
Promise.<Core.PDFNet.Filter>

seek(offset, origin)

When overridden in a derived class, sets the position within the current stream.
Parameters:
Name Type Description
offset number A byte offset relative to origin. If offset is negative, the new position will precede the position specified by origin by the number of bytes specified by offset. If offset is zero, the new position will be the position specified by origin. If offset is positive, the new position will follow the position specified by origin by the number of bytes specified by offset.
origin number 
PDFNet.Filter.ReferencePos = {
	e_begin : 0
	e_end : 2
	e_cur : 1
}
A value of type ReferencePos indicating the reference point used to obtain the new position Note: After each Seek() operation the number of consumed bytes (i.e. Count()) is set to 0.
Returns:
Type
Promise.<void>

setCount(new_count)

Sets a new counting point for the current filter. All subsequent Consume() operations will increment this counter. Make sure that the output filter is flushed before using SetCount().
Parameters:
Name Type Description
new_count number number to set the counting point of the filter to.
Returns:
A promise that resolves to the value of previous counter
Type
Promise.<number>

setStreamLength(bytes)

The functions specifies the length of the data stream. The default implementation doesn't do anything. For some derived filters such as file segment filter it may be useful to override this function in order to limit the stream length.
Parameters:
Name Type Description
bytes number the length of stream in bytes
Returns:
Type
Promise.<void>

size()

Returns:
A promise that resolves to the size of buffer returned by Begin(). If the Size() returns 0 end of data has been reached.
Type
Promise.<number>

takeOwnership()

Take the ownership of this object, so that PDFNet.runWithCleanup won't destroy this object.
Inherited From:
Returns:
Type
void

tell()

Reports the current read position in the stream relative to the stream origin.
Returns:
A promise that resolves to The current position in the stream
Type
Promise.<number>

truncate(new_size)

Truncates the underlying data. This method is for a writeable, seekable filter only and will throw otherwise. Note: For a filter representing a file, truncation would mean resizing the file.
Parameters:
Name Type Description
new_size number the number of bytes to resize the filter to
Returns:
A promise that resolves to The new size of the filter
Type
Promise.<number>