README
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Note
This package is an improved version of x/image/tiff featuring:
- Read support for CCITT Group3/4 compressed images using x/image/ccitt
- Read/write support for LZW compressed images using github.com/hhrutter/lzw
- Read/write support for the CMYK color model.
Background
Working on pdfcpu (a PDF processor) created a need for processing TIFF files and LZW compression in details beyond the standard library.
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CCITT compression for monochrome images was the first need. This is being addressed as part of ongoing work on x/image/ccitt.
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As stated in this golang proposal Go LZW implementations are spread out over the standard library at compress/lzw and x/image/tiff/lzw. As of Go 1.12 compress/lzw works reliably for GIF only. This is also the reason the TIFF package at x/image/tiff provides its own lzw implementation for compression. With PDF there is a third variant of lzw needed for reading/writing lzw compressed PDF object streams and processing embedded TIFF images. github.com/hhrutter/lzw fills this gap. It is an extended version of compress/lzw supporting GIF, PDF and TIFF.
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The PDF specification defines a CMYK color space. This is currently not supported at x/image/tiff.
Goal
An improved version of x/image/tiff with full read/write support for CCITT, LZW compression and the CMYK color model.
Documentation
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Overview ¶
Package tiff is an enhanced version of x/image/tiff.
It uses a consolidated version of compress/lzw (https://github.com/hhrutter/lzw) for compression and also adds support for CMYK.
More information: https://github.com/hhrutter/tiff
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Decode ¶
Decode reads a TIFF image from r and returns it as an image.Image. The type of Image returned depends on the contents of the TIFF.
func DecodeConfig ¶
DecodeConfig returns the color model and dimensions of a TIFF image without decoding the entire image.
Types ¶
type CompressionType ¶
type CompressionType int
CompressionType describes the type of compression used in Options.
const ( Uncompressed CompressionType = iota Deflate LZW CCITTGroup3 CCITTGroup4 )
Constants for supported compression types.
type FormatError ¶
type FormatError string
A FormatError reports that the input is not a valid TIFF image.
func (FormatError) Error ¶
func (e FormatError) Error() string
type Options ¶
type Options struct {
// Compression is the type of compression used.
Compression CompressionType
// Predictor determines whether a differencing predictor is used;
// if true, instead of each pixel's color, the color difference to the
// preceding one is saved. This improves the compression for certain
// types of images and compressors. For example, it works well for
// photos with Deflate compression.
Predictor bool
}
Options are the encoding parameters.
type UnsupportedError ¶
type UnsupportedError string
An UnsupportedError reports that the input uses a valid but unimplemented feature.
func (UnsupportedError) Error ¶
func (e UnsupportedError) Error() string
Source Files