goldsmith/plugins/thumbnail/thumbnail.go

144 lines
3.6 KiB
Go

// Package thumbnail automatically generates thumbnails for a variety of common
// image formats and saves them to a user-configurable path.
package thumbnail
import (
"bytes"
"errors"
"fmt"
"image/color"
"path/filepath"
"strings"
"git.foosoft.net/alex/goldsmith"
"git.foosoft.net/alex/goldsmith/filters/wildcard"
"github.com/disintegration/imaging"
)
// Namer callback function builds thumbnail file paths based on the original file path.
// An empty path can be returned if a thumbnail should not be generated for the current file.
type Namer func(string, int) string
// Desired thumbnailing styles.
type Style int
const (
Fit Style = iota
Crop
Pad
)
// Thumbnail chainable context.
type Thumbnail struct {
size int
style Style
color color.Color
namer Namer
}
// New creates a new instance of the Thumbnail plugin.
func New() *Thumbnail {
namer := func(path string, dims int) string {
ext := filepath.Ext(path)
body := strings.TrimSuffix(path, ext)
return fmt.Sprintf("%s-thumb.png", body)
}
return &Thumbnail{
128,
Fit,
color.Transparent,
namer,
}
}
// Size sets the desired maximum pixel size of generated thumbnails (default: 128).
func (self *Thumbnail) Size(dims int) *Thumbnail {
self.size = dims
return self
}
// Style sets the desired thumbnailing style.
func (self *Thumbnail) Style(style Style) *Thumbnail {
self.style = style
return self
}
// Namer sets the callback used to build paths for thumbnail files.
// Default naming appends "-thumb" to the path and changes extension to PNG,
// for example "file.jpg" becomes "file-thumb.png".
func (self *Thumbnail) Namer(namer Namer) *Thumbnail {
self.namer = namer
return self
}
func (*Thumbnail) Name() string {
return "thumbnail"
}
func (*Thumbnail) Initialize(context goldsmith.Context) error {
context.Filter(wildcard.New("**/*.jpg", "**/*.jpeg", "**/*.gif", "**/*.png"))
return nil
}
func (self *Thumbnail) Process(context goldsmith.Context, inputFile goldsmith.File) error {
defer context.DispatchFile(inputFile)
thumbPath := self.namer(inputFile.Path(), self.size)
if len(thumbPath) == 0 {
return nil
}
if outputFile := context.RetrieveCachedFile(thumbPath, inputFile); outputFile != nil {
outputFile.CopyProps(inputFile)
context.DispatchFile(outputFile)
return nil
}
outputFile, err := self.thumbnail(context, inputFile, thumbPath)
if err != nil {
return err
}
context.DispatchAndCacheFile(outputFile, inputFile)
return nil
}
func (self *Thumbnail) thumbnail(context goldsmith.Context, inputFile goldsmith.File, thumbPath string) (goldsmith.File, error) {
var thumbFormat imaging.Format
switch strings.ToLower(filepath.Ext(thumbPath)) {
case ".jpg", ".jpeg":
thumbFormat = imaging.JPEG
case ".gif":
thumbFormat = imaging.GIF
case ".png":
thumbFormat = imaging.PNG
default:
return nil, errors.New("unsupported image format")
}
thumbImage, err := imaging.Decode(inputFile)
if err != nil {
return nil, err
}
switch self.style {
case Fit:
thumbImage = imaging.Fit(thumbImage, self.size, self.size, imaging.Lanczos)
case Crop:
thumbImage = imaging.Fill(thumbImage, self.size, self.size, imaging.Center, imaging.Lanczos)
case Pad:
thumbImage = imaging.Fit(thumbImage, self.size, self.size, imaging.Lanczos)
thumbImage = imaging.PasteCenter(imaging.New(self.size, self.size, self.color), thumbImage)
default:
return nil, errors.New("unsupported thumbnailing style")
}
var thumbBuff bytes.Buffer
if err := imaging.Encode(&thumbBuff, thumbImage, thumbFormat); err != nil {
return nil, err
}
return context.CreateFileFromReader(thumbPath, &thumbBuff)
}