Reference

TWAIN Module API

Functions

twain.DIBToBMFile()

This method is used to convert a DIB (Device Independent Bitmap) to a windows bitmap file format. The BMP file is either returned as a string, or written to a file with the name given in the second argument.

Parameters

Name Description Default Value
hBitmap A global handle as returned from the Source.XferImageNatively() function. mandatory
FileName A string supplying a file name. If not passed, the BMP file will be returned as a string.

This method returns a single value, which is either the BMP file as a string, or None. On failure it raises the following exceptions:

Exception Meaning

twain.DIBToXBMFile()

This method is used to convert a DIB (Device Independent Bitmap) to an X-Windows bitmap file format. The XBM file is either returned as a string, or written to a file with the name given in the third argument.

Parameters

Name Description Default Value
hBitmap A global handle as returned from the Source.XferImageNatively() function. mandatory
Prefix A string supplying the prefix (XBM id). This is normally the file name excluding the .xbm suffix. mandatory
FileName A string supplying a file name. If not passed, the XBM file will be returned as a string.

This method returns a single value, which is either the XBM file as a string, or None. On failure it raises the following exceptions:

Exception Meaning

twain.GlobalHandleAllocate()

This method provides the application with access to the Windows Global Heap. It allocates a handler of a specific size.

Parameters

Name Description Default Value
lSize The size of the memory buffer required. mandatory

This method allocates the required memory and returns a handle to the memory. If the function fails, it returns None.

twain.GlobalHandleGetBytes()

This method provides the application with access to the Windows Global Heap. It returns a specified number of bytes from the Global Heap location, identified by the handle.

Parameters

Name Description Default Value
Handle A handle returned by GlobalHandleAllocate(), or XferImageNatively(). mandatory
Offset An integer giving the offset in the buffer at which to begin the read. mandatory
Length The number of bytes to read from the buffer. mandatory

This method returns a python string, which contains the identified data.

twain.GlobalHandlePutBytes()

This method provides the application with access to the Windows Global Heap. It writes a python string to Global Heap location, identified by the handle.

This method does not return any values.

twain.GlobalHandleFree()

This method provides the application with access to the Windows Global Heap. It releases the Global Heap location, identified by the handle.

Parameters

Name Description Default Value
Handle A handle returned by GlobalHandleAllocate(), or XferImageNatively(). mandatory

twain.Version()

Returns the version identifier for the Python TWAIN interface.

Variables

A large number of constants are defined in the TWAIN module. These are used with various API calls. They are broken down by their prefixes, as follows:

Prefix	Purpose
ACAP_	Audio Capabilities
CAP_	General Capabilities
DAT_	Describe the types of data structures
DG_	Identify Data Groups (i.e. images/audio)
ICAP_	Identify Image Capabilities
MSG_	Message Identifiers for communcations with Source
TWAF_	Audio File Formats
TWAL_	Alarm Codes
TWBCOR_	Barcode Rotation
TWBD_	Barcode Search Mode
TWBO_	Bit-order
TWBR_	Bit-depth Reduction
TWBT_	Barcode Type
TWCB_	Clear Buffesr
TWCC_	Condition Codes (errors)
TWCP_	Compression Options
TWCY_	Country Constants
TWDE_	Device Events
TWDSK_	de-skew
TWDX_	Duplication Options
TWEI_	Extended Image Information
TWEJ_	Not defined in specification* (appear to relate to ejection of originals)
TWFA_	Feeded Alignment
TWFF_	File Formats (Image)
TWFL_	Flash Used
TWFO_	Feeder Order
TWFR_	Flip Rotation
TWFS_	File System
TWFT_	Filter Type
TWFY_	File System - File Type
TWIF_	Image Filter
TWJC_	Job Control
TWLG_	Language Ids
TWLP_	Light Path
TWLS_	Light Source
TWMF_	Memory Flags
TWNF_	Noise Filter
TWON_	Protocol Version Identifiers
TWOR_	Orientation
TWOV_	Overscan
TWPA_	Colour Palette types
TWPCH_	Extend Image (TWEI) Patch Codes
TWPC_	Planar/Chunky selection
TWPF_	Pixel Flavour
TWPM_	Printer Mode
TWPR_	Printer Codes
TWPS_	Power Supply
TWPT_	Pixel Type
TWQC_	Query Capability Options
TWRC_	Return Codes
TWSS_	Supported Sizes
TWSX_	Transfer Mechanism
TWTY_	TWAIN Primitive Types
TWUN_	Image Units

Reference

Name	Description	Default Value
hBitmap	A global handle as returned from the Source.XferImageNatively() function.	mandatory
FileName	A string supplying a file name.	If not passed, the BMP file will be returned as a string.