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