thumbnail/Thumbnailer.go

package thumbnail

import (
	"fmt"
	"image/jpeg"
	"image/png"
	"os"
	"strings"

	lru "github.com/hashicorp/golang-lru"
)

type Thumbnailer struct {
	Width  int
	Height int

	thumbCache *lru.Cache // threadsafe
}

func NewThumbnailer(Width, Height, MaxCacheSize int) *Thumbnailer {
	thumbCache, err := lru.New(MaxCacheSize)
	if err != nil {
		panic(err)
	}

	return &Thumbnailer{
		Width:      Width,
		Height:     Height,
		thumbCache: thumbCache,
	}
}

func (this *Thumbnailer) RenderFile(absPath string) ([]byte, error) {

	thumb, ok := this.thumbCache.Get(absPath)
	if ok {
		return thumb.([]byte), nil
	}

	// Add to cache
	thumb, err := this.RenderFile_NoCache(absPath)
	if err != nil {
		return nil, err
	}

	this.thumbCache.Add(absPath, thumb)
	return thumb.([]byte), nil
}

func (this *Thumbnailer) RenderFile_NoCache(absPath string) ([]byte, error) {

	fh, err := os.OpenFile(absPath, os.O_RDONLY, 0400)
	if err != nil {
		return nil, err
	}

	defer fh.Close()

	if len(absPath) < 4 {
		return nil, fmt.Errorf("No extension on filename")
	}
	extension := strings.ToLower(absPath[len(absPath)-4:])

	switch extension {
	case ".jpg", "jpeg":
		src, err := jpeg.Decode(fh)
		if err != nil {
			return nil, err
		}

		return this.RenderScaledImage(src)

	case ".png":
		src, err := png.Decode(fh)
		if err != nil {
			return nil, err
		}

		return this.RenderScaledImage(src)

	case ".avi", ".mkv", ".mp4", ".ogm", ".wmv":
		return this.RenderScaledFfmpeg(absPath)

	default:
		return nil, fmt.Errorf("No thumbnailer for file type")

	}

}