thumb

Documentation

Overview

Package thumb implements a lazy image thumbnail cache. Supported input image formats are any format Go can decode natively from the standard library and subrepo golang.org/x/image.

Index

• func DecodeFunc(name string) func(io.Reader) (image.Image, error)
• func FormatSupported(ext string) bool
• type Cache
  • func NewCache(dirPath string, enc Encoder, store FileStore, scaler draw.Scaler) (*Cache, error)
  • func (c *Cache) Get(id string, w, h int) string
  • func (c *Cache) Purge() error
  • func (c *Cache) Remove(id string) error
  • func (c *Cache) Serve()
  • func (c *Cache) Size() int64
• type Encoder
• type FileStore
• type JPEGEncoder
  • func (e JPEGEncoder) Encode(dst io.Writer, thumb image.Image) error
  • func (JPEGEncoder) Extension() string

Functions

func DecodeFunc

func DecodeFunc(name string) func(io.Reader) (image.Image, error)

DecodeFunc returns a func that can be used to decode the image with the given file name, or nil if it's not supported. TODO: sniff magic number instead of only using file extension TODO: allow externally registered format decoders

func FormatSupported

func FormatSupported(ext string) bool

FormatSupported returns true if the given file extension belongs to an image format that can be thumbnailed by this package.

Types

type Cache

type Cache struct {
	// contains filtered or unexported fields
}

Cache is a lazy, concurrent thumbnail cache for airlift-server with request batching for on-the-fly thumbnail generation. Only file paths are cached in memory.

func NewCache

func NewCache(dirPath string, enc Encoder, store FileStore, scaler draw.Scaler) (*Cache, error)

NewCache initializes a new thumbnail generator that stores files encoded from store by enc in dirPath, using scaler to resample images.

func (*Cache) Get

func (c *Cache) Get(id string, w, h int) string

Get returns the file path to the thumbnail of the file with the given id, generating it if it doesn't exist already. If concurrent requests are made to the same non-existent thumbnail, it will only be generated once.

TODO: error handling

func (*Cache) Purge

func (c *Cache) Purge() error

Purge removes all thumbnails from c.

func (*Cache) Remove

func (c *Cache) Remove(id string) error

Remove deletes all sizes of thumbnail of a given file.

func (*Cache) Serve

func (c *Cache) Serve()

Serve starts the cache request server, blocking forever. It should be launched in its own goroutine before any requests are made.

func (*Cache) Size

func (c *Cache) Size() int64

Size returns the total size of all of the thumbnails contained in c in bytes.

type Encoder

type Encoder interface {
	Extension() string // The file extension of the resulting image
	Encode(dst io.Writer, thumb image.Image) error
}

Encoder describes a way to encode a thumbnail image.

type FileStore

type FileStore interface {
	// Get should return the path to the file on disk, or the empty string if
	// not found.
	Get(id string) string
}

FileStore is a source of files that Cache will reference.

type JPEGEncoder

type JPEGEncoder struct{ *jpeg.Options }

JPEGEncoder is an Encoder that encodes JPEG files.

func (JPEGEncoder) Encode

func (e JPEGEncoder) Encode(dst io.Writer, thumb image.Image) error

func (JPEGEncoder) Extension

func (JPEGEncoder) Extension() string