Class: Filter

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.

Methods


<static> createCustomWithStruct(mode, user_data, callbacks)

Parameters:
Name Type Description
mode number/enum
PDFNet.Filter.StdFileOpenMode = {
	e_read_mode : 0
	e_write_mode : 1
	e_append_mode : 2
}
user_data
callbacks
Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

<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 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
PDFNet.Filter

<static> createImage2RGB(img)

Parameters:
Name Type Description
img PDFNet.Image
Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

<static> createImage2RGBA(img, premultiply)

Parameters:
Name Type Description
img PDFNet.Image
premultiply boolean
Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

<static> createImage2RGBAFromElement(elem, premultiply)

Parameters:
Name Type Description
elem PDFNet.Element
premultiply boolean
Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

<static> createImage2RGBAFromObj(obj, premultiply)

Parameters:
Name Type Description
obj PDFNet.Obj
premultiply boolean
Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

<static> createImage2RGBFromElement(elem)

Parameters:
Name Type Description
elem PDFNet.Element
Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

<static> createImage2RGBFromObj(obj)

Parameters:
Name Type Description
obj PDFNet.Obj
Returns:

A promise that resolves to an object of type: "Filter"

Type
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: "Filter"

Type
PDFNet.Filter

attachFilter(attach_filter)

Parameters:
Name Type Description
attach_filter PDFNet.Filter

begin()

Returns:

A promise that resolves to beginning of the buffer of Size() bytes that can be used to read or write data.

Type
number

canSeek()

Returns:

A promise that resolves to true if the stream supports seeking; otherwise, false.
default is to return false.

Type
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().


count()

Returns:

A promise that resolves to the number of bytes consumed since opening the filter or the last Seek operation

Type
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: "Filter"

Type
PDFNet.Filter

createInputIterator()

Create Filter iterator. Filter iterator similar to a regular filter. However, there can be only one owner of the attached filter.

Returns:

A promise that resolves to an object of type: "Filter"

Type
PDFNet.Filter

destroy()

Frees the native memory of the object.


flush()

Forces any data remaining in the buffer to be written to input or output filter.


flushAll()

Forces any data remaining in the filter chain to the source or destination.


getAttachedFilter()

Returns:

A promise that resolves to returns attached Filter or a NULL filter if no filter is attached.

Type
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
string

getFilePath()

Returns:

A promise that resolves to the file path to the underlying file stream. Default implementation returns empty string.

Type
string

getName()

Returns:

A promise that resolves to descriptive name of the filter.

Type
string

getSourceFilter()

Returns:

A promise that resolves to returns the first filter in the chain (usually a file filter)

Type
PDFNet.Filter

isInputFilter()

Returns:

A promise that resolves to boolean indicating whether this is an input filter.

Type
boolean

memoryFilterGetBuffer()

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
number

memoryFilterReset()


memoryFilterSetAsInputFilter()


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
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/enum
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


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
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


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
number

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
number