rez

README

rez

Package rez provides image resizing in pure Go and SIMD.

Download:

go get github.com/bamiaux/rez

Full documentation at http://godoc.org/github.com/bamiaux/rez

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Package rez provides image resizing in pure Go and SIMD.

Featuring:

- YCbCr, RGBA, NRGBA & Gray resizes
- YCbCr Chroma subsample ratio conversions
- Optional interlaced-aware resizes
- Parallel resizes
- SIMD optimisations on AMD64

The easiest way to use it is:

err := Convert(output, input, NewBicubicFilter())

However, if you plan to convert video, where resize parameters are the same for multiple images, the best way is:

cfg, err := PrepareConversion(output, input)
converter, err := NewConverter(cfg, NewBicubicFilter())
for i := 0; i < N; i++ {
    err := converter.Convert(output[i], input[i])
}

Note that by default, images are resized in parallel with GOMAXPROCS slices. Best performance is obtained when GOMAXPROCS is at least equal to your CPU count.

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Automatically generated by autoreadme on 2014.11.25

Documentation

Overview

Package rez provides image resizing in pure Go and SIMD.

Featuring:

• YCbCr, RGBA, NRGBA & Gray resizes
• YCbCr Chroma subsample ratio conversions
• Optional interlaced-aware resizes
• Parallel resizes
• SIMD optimisations on AMD64

The easiest way to use it is:

err := Convert(output, input, NewBicubicFilter())

However, if you plan to convert video, where resize parameters are the same for multiple images, the best way is:

cfg, err := PrepareConversion(output, input)
converter, err := NewConverter(cfg, NewBicubicFilter())
for i := 0; i < N; i++ {
    err := converter.Convert(output[i], input[i])
}

Note that by default, images are resized in parallel with GOMAXPROCS slices. Best performance is obtained when GOMAXPROCS is at least equal to your CPU count.

Index

• Constants
• func Convert(output, input image.Image, filter Filter) error
• func DumpImage(prefix string, img image.Image) error
• func Psnr(a, b image.Image) ([]float64, error)
• type ChromaRatio
  • func GetRatio(value image.YCbCrSubsampleRatio) ChromaRatio
• type Converter
  • func NewConverter(cfg *ConverterConfig, filter Filter) (Converter, error)
• type ConverterConfig
  • func PrepareConversion(output, input image.Image) (*ConverterConfig, error)
• type Descriptor
  • func (d *Descriptor) Check() error
  • func (d *Descriptor) GetHeight(plane int) int
  • func (d *Descriptor) GetWidth(plane int) int
• type Filter
  • func NewBicubicFilter() Filter
  • func NewBilinearFilter() Filter
  • func NewCustomBicubicFilter(b, c float64) Filter
  • func NewLanczosFilter(alpha int) Filter
• type Plane
• type Resizer
  • func NewResize(cfg *ResizerConfig, filter Filter) Resizer
• type ResizerConfig

Constants

const (
	// Bits exports the number of significant bits used by kernels
	Bits = 14
)

Functions

func Convert

func Convert(output, input image.Image, filter Filter) error

Convert converts an input image into output, applying any color conversion and/or resizing, using the input filter for interpolation. Note that if you plan to do the same conversion over and over, it is faster to use a Converter interface

func DumpImage

func DumpImage(prefix string, img image.Image) error

DumpImage dumps each img planes to disk using the input prefix

func Psnr

func Psnr(a, b image.Image) ([]float64, error)

Psnr computes the PSNR between two input images Only ycbcr is currently supported

Types

type ChromaRatio

type ChromaRatio int

ChromaRatio is a chroma subsampling ratio

const (
	// Ratio410 is 4:1:0
	Ratio410 ChromaRatio = iota
	// Ratio411 is 4:1:1
	Ratio411
	// Ratio420 is 4:2:0
	Ratio420
	// Ratio422 is 4:2:2
	Ratio422
	// Ratio440 is 4:4:0
	Ratio440
	// Ratio444 is 4:4:4
	Ratio444
)

func GetRatio

func GetRatio(value image.YCbCrSubsampleRatio) ChromaRatio

GetRatio returns a ChromaRatio from an image.YCbCrSubsampleRatio

type Converter

type Converter interface {
	// Converts one image into another, applying any necessary colorspace
	// conversion and/or resizing
	// dst = destination image
	// src = source image
	// Result is undefined if src points to the same data as dst
	// Returns an error if the conversion fails
	Convert(dst, src image.Image) error
}

Converter is an interface that implements conversion between images It is currently able to convert only between ycbcr images

func NewConverter

func NewConverter(cfg *ConverterConfig, filter Filter) (Converter, error)

NewConverter returns a Converter interface cfg = converter configuration filter = filter used for resizing Returns an error if the conversion is invalid or not implemented

type ConverterConfig

type ConverterConfig struct {
	Input      Descriptor // input description
	Output     Descriptor // output description
	Threads    int        // number of allowed "threads"
	DisableAsm bool       // disable asm optimisations
}

ConverterConfig is a configuration used with NewConverter

func PrepareConversion

func PrepareConversion(output, input image.Image) (*ConverterConfig, error)

PrepareConversion returns a ConverterConfig properly set for a conversion from input images to output images Returns an error if the conversion is not possible

type Descriptor

type Descriptor struct {
	Width      int         // width in pixels
	Height     int         // height in pixels
	Ratio      ChromaRatio // chroma ratio
	Pack       int         // pixels per pack
	Interlaced bool        // progressive or interlaced
	Planes     int         // number of planes
}

Descriptor describes an image properties

func (*Descriptor) Check

func (d *Descriptor) Check() error

Check returns whether the descriptor is valid

func (*Descriptor) GetHeight

func (d *Descriptor) GetHeight(plane int) int

GetHeight returns the height in pixels for the input plane

func (*Descriptor) GetWidth

func (d *Descriptor) GetWidth(plane int) int

GetWidth returns the width in pixels for the input plane

type Filter

type Filter interface {
	Taps() int
	Name() string
	Get(dx float64) float64
}

Filter is an interpolation filter interface It is used to compute weights for every input pixel

func NewBicubicFilter

func NewBicubicFilter() Filter

NewBicubicFilter exports a classic bicubic filter

func NewBilinearFilter

func NewBilinearFilter() Filter

NewBilinearFilter exports a bilinear filter

func NewCustomBicubicFilter

func NewCustomBicubicFilter(b, c float64) Filter

NewCustomBicubicFilter exports a bicubic filter where <b> and <c> can be customized. For example, the Mitchell-Netravali bicubic filter is b = c = 1/3

func NewLanczosFilter

func NewLanczosFilter(alpha int) Filter

NewLanczosFilter exports a lanczos filter where <alpha> is filter size

type Plane

type Plane struct {
	Data   []byte // plane buffer
	Width  int    // width in pixels
	Height int    // height in pixels
	Pitch  int    // pitch in bytes
	Pack   int    // pixels per pack
}

Plane describes a single image plane

type Resizer

type Resizer interface {
	// Resize one plane into another
	// dst, src = destination and source buffer
	// width, height = plane dimensions in pixels
	// dstPitch, srcPitch = destination and source pitchs/strides in bytes
	Resize(dst, src []byte, width, height, dstPitch, srcPitch int)
}

Resizer is a interface that implements resizes

func NewResize

func NewResize(cfg *ResizerConfig, filter Filter) Resizer

NewResize returns a new resizer cfg = resize configuration filter = filter used for computing weights

type ResizerConfig

type ResizerConfig struct {
	Depth      int  // bits per pixel
	Input      int  // input size in pixels
	Output     int  // output size in pixels
	Vertical   bool // true for vertical resizes
	Interlaced bool // true if input/output is interlaced
	Pack       int  // pixels per pack [default=1]
	Threads    int  // number of threads, [default=0]
	DisableAsm bool // disable asm optimisations
}

ResizerConfig is a configuration used with NewResizer