ccitt

package
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Published: Jun 4, 2024 License: BSD-3-Clause Imports: 5 Imported by: 54

Documentation

Overview

Package ccitt implements a CCITT (fax) image decoder.

Index

Constants

View Source
const AutoDetectHeight = -1

AutoDetectHeight is passed as the height argument to NewReader to indicate that the image height (the number of rows) is not known in advance.

Variables

This section is empty.

Functions

func DecodeIntoGray

func DecodeIntoGray(dst *image.Gray, r io.Reader, order Order, sf SubFormat, opts *Options) error

DecodeIntoGray decodes the CCITT-formatted data in r into dst.

It returns an error if dst's width and height don't match the implied width and height of CCITT-formatted data.

func NewReader

func NewReader(r io.Reader, order Order, sf SubFormat, width int, height int, opts *Options) io.Reader

NewReader returns an io.Reader that decodes the CCITT-formatted data in r. The resultant byte stream is one bit per pixel (MSB first), with 1 meaning white and 0 meaning black. Each row in the result is byte-aligned.

A negative height, such as passing AutoDetectHeight, means that the image height is not known in advance. A negative width is invalid.

Types

type Options

type Options struct {
	// Align means that some variable-bit-width codes are byte-aligned.
	Align bool
	// Invert means that black is the 1 bit or 0xFF byte, and white is 0.
	Invert bool
}

Options are optional parameters.

type Order

type Order uint32

Order specifies the bit ordering in a CCITT data stream.

const (
	// LSB means Least Significant Bits first.
	LSB Order = iota
	// MSB means Most Significant Bits first.
	MSB
)

type SubFormat

type SubFormat uint32

SubFormat represents that the CCITT format consists of a number of sub-formats. Decoding or encoding a CCITT data stream requires knowing the sub-format context. It is not represented in the data stream per se.

const (
	Group3 SubFormat = iota
	Group4
)

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