bimg/README.md

# bimg [![Build Status](https://travis-ci.org/h2non/bimg.png)](https://travis-ci.org/h2non/bimg) [![GitHub release](https://img.shields.io/github/tag/h2non/bimg.svg)](https://github.com/h2non/bimg/releases) [![GoDoc](https://godoc.org/github.com/h2non/bimg?status.png)](https://godoc.org/github.com/h2non/bimg) [![Coverage Status](https://coveralls.io/repos/h2non/bimg/badge.svg?branch=master)](https://coveralls.io/r/h2non/bimg?branch=master)

Small [Go](http://golang.org) library for blazing fast and efficient image processing based on [libvips](https://github.com/jcupitt/libvips) using C bindings. It provides a clean, simple and fluent [API](#examples) in pure Go.

bimg is designed to be a small and efficient library with a generic and useful set of features. 
It uses internally libvips, which requires a [low memory footprint](http://www.vips.ecs.soton.ac.uk/index.php?title=Speed_and_Memory_Use) 
and it's typically 4x faster than using the quickest ImageMagick and GraphicsMagick settings or Go  native `image` package, and in some cases it's even 8x faster processing JPEG images. 

It can read JPEG, PNG, WEBP and TIFF formats and output to JPEG, PNG and WEBP. It supports common [image transformation](#supported-image-operations) operations such as crop, resize, rotate... and conversion between multiple formats. 

For getting started, take a look to the [examples](#examples) and [programmatic API](https://godoc.org/github.com/h2non/bimg) documentation.

bimg was heavily inspired in [sharp](https://github.com/lovell/sharp), 
its homologous package built for node.js by [Lovell Fuller](https://github.com/lovell).

**Note**: bimg is still beta. Pull request and issues are highly appreciated

## Prerequisites

- [libvips](https://github.com/jcupitt/libvips) v7.40.0+ (7.42.0+ recommended)
- C compatible compiler such as gcc 4.6+ or clang 3.0+
- Go 1.3+

## Installation

```bash
go get -u gopkg.in/h2non/bimg.v0
```

### libvips

Run the following script as `sudo` (supports OSX, Debian/Ubuntu, Redhat, Fedora, Amazon Linux):
```bash
curl -s https://raw.githubusercontent.com/lovell/sharp/master/preinstall.sh | sudo bash -
```

The [install script](https://github.com/lovell/sharp/blob/master/preinstall.sh) requires `curl` and `pkg-config`

## Supported image operations

- Resize
- Enlarge
- Crop
- Rotate
- Auto-rotate (based on EXIF orientation)
- Flip
- Flop
- Thumbnail
- Extract area
- Format conversion
- EXIF metadata (size, alpha channel, profile, orientation...)

## Performance

libvips is probably the faster open source solution for image processing. 
Here you can see some performance test comparisons for multiple scenarios:

- [libvips speed and memory usage](http://www.vips.ecs.soton.ac.uk/index.php?title=Speed_and_Memory_Use)
- [sharp performance tests](https://github.com/lovell/sharp#the-task) 

#### Benchmarks

Tested using Go 1.4 and libvips-7.42.3 in OSX i7 2.7Ghz
```
PASS
BenchmarkResizeLargeJpeg  30    46652408 ns/op
BenchmarkResizePng        20    57387902 ns/op
BenchmarkResizeWebP       500    2453220 ns/op
BenchmarkConvertToJpeg    30    35556414 ns/op
BenchmarkCrop             30    51768475 ns/op
BenchmarkExtract          30    50866406 ns/op
ok 9.424s
```

## API

### Examples

```go
import (
  "fmt"
  "os"
  "gopkg.in/h2non/bimg.v0"
)
```

#### Resize

```go
buffer, err := bimg.Read("image.jpg")
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

newImage, err := bimg.NewImage(buffer).Resize(800, 600)
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

size, err := bimg.NewImage(newImage).Size()
if size.Width == 400 && size.Height == 300 {
  fmt.Println("The image size is valid")
}

bimg.Write("new.jpg", newImage)
```

#### Rotate

```go
buffer, err := bimg.Read("image.jpg")
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

newImage, err := bimg.NewImage(buffer).Rotate(90)
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

bimg.Write("new.jpg", newImage)
```

#### Convert

```go
buffer, err := bimg.Read("image.jpg")
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

newImage, err := bimg.NewImage(buffer).Convert(bimg.PNG)
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

if bimg.NewImage(newImage).Type() == "png" {
  fmt.Fprintln(os.Stderr, "The image was converted into png")
}
```

#### Custom options

See [Options](https://godoc.org/github.com/h2non/bimg#Options) struct to discover all the available fields

```go
options := bimg.Options{
  Width:        800,
  Height:       600,
  Crop:         true,
  Quality:      95,
  Rotate:       180,
}

buffer, err := bimg.Read("image.jpg")
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

newImage, err := bimg.NewImage(buffer).Process(options)
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

bimg.Write("new.jpg", newImage)
```

#### Fluent interface

```go
buffer, err := bimg.Read("image.jpg")
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

image := bimg.NewImage(buffer)

// first crop image
_, err := image.CropByWidth(300)
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

// then flip it
newImage, err := image.Flip()
if err != nil {
  fmt.Fprintln(os.Stderr, err)
}

// save the cropped and flipped image
bimg.Write("new.jpg", newImage)
```


#### func  DetermineImageTypeName

```go
func DetermineImageTypeName(buf []byte) string
```

#### func  Initialize

```go
func Initialize()
```

#### func  IsTypeNameSupported

```go
func IsTypeNameSupported(t string) bool
```

#### func  IsTypeSupported

```go
func IsTypeSupported(t ImageType) bool
```

#### func  Read

```go
func Read(path string) ([]byte, error)
```

#### func  Resize

```go
func Resize(buf []byte, o Options) ([]byte, error)
```

#### func  Shutdown

```go
func Shutdown()
```

#### func  Write

```go
func Write(path string, buf []byte) error
```

#### type Angle

```go
type Angle int
```


```go
const (
  D0   Angle = C.VIPS_ANGLE_D0
  D90  Angle = C.VIPS_ANGLE_D90
  D180 Angle = C.VIPS_ANGLE_D180
  D270 Angle = C.VIPS_ANGLE_D270
)
```

#### type Direction

```go
type Direction int
```


```go
const (
  HORIZONTAL Direction = C.VIPS_DIRECTION_HORIZONTAL
  VERTICAL   Direction = C.VIPS_DIRECTION_VERTICAL
)
```

#### type Gravity

```go
type Gravity int
```


```go
const (
  CENTRE Gravity = iota
  NORTH
  EAST
  SOUTH
  WEST
)
```

#### type Image

```go
type Image struct {
}
```


#### func  NewImage

```go
func NewImage(buf []byte) *Image
```

#### func (*Image) Convert

```go
func (i *Image) Convert(t ImageType) ([]byte, error)
```

#### func (*Image) Crop

```go
func (i *Image) Crop(width, height int) ([]byte, error)
```

#### func (*Image) Extract

```go
func (i *Image) Extract(top, left, width, height int) ([]byte, error)
```

#### func (*Image) Flip

```go
func (i *Image) Flip() ([]byte, error)
```

#### func (*Image) Metadata

```go
func (i *Image) Metadata() (ImageMetadata, error)
```

#### func (*Image) Process

```go
func (i *Image) Process(o Options) ([]byte, error)
```

#### func (*Image) Resize

```go
func (i *Image) Resize(width, height int) ([]byte, error)
```

#### func (*Image) Rotate

```go
func (i *Image) Rotate(a Angle) ([]byte, error)
```

#### func (*Image) Size

```go
func (i *Image) Size() (ImageSize, error)
```

#### func (*Image) Thumbnail

```go
func (i *Image) Thumbnail(pixels int) ([]byte, error)
```

#### func (*Image) Type

```go
func (i *Image) Type() string
```

#### type ImageMetadata

```go
type ImageMetadata struct {
  Orientation int
  Channels    int
  Alpha       bool
  Profile     bool
  Type        string
  Space       string
  Size        ImageSize
}
```


#### func  Metadata

```go
func Metadata(buf []byte) (ImageMetadata, error)
```

#### type ImageSize

```go
type ImageSize struct {
  Width  int
  Height int
}
```


#### func  Size

```go
func Size(buf []byte) (ImageSize, error)
```

#### type ImageType

```go
type ImageType int
```


```go
const (
  UNKNOWN ImageType = iota
  JPEG
  WEBP
  PNG
  TIFF
  MAGICK
)
```

#### func  DetermineImageType

```go
func DetermineImageType(buf []byte) ImageType
```

#### type Interpolator

```go
type Interpolator int
```


```go
const (
  BICUBIC Interpolator = iota
  BILINEAR
  NOHALO
)
```

#### func (Interpolator) String

```go
func (i Interpolator) String() string
```

#### type Options

```go
type Options struct {
  Height       int
  Width        int
  AreaHeight   int
  AreaWidth    int
  Top          int
  Left         int
  Crop         bool
  Enlarge      bool
  Extend       int
  Embed        bool
  Quality      int
  Compression  int
  Type         ImageType
  Rotate       Angle
  Flip         Direction
  Gravity      Gravity
  Interpolator Interpolator
}
```


## License

MIT - Tomas Aparicio