thumbnail/Thumbnailer.go

package thumbnail

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

type Thumbnailer struct {
	Width        int
	Height       int
	MaxCacheSize int

	cacheMtx   sync.RWMutex
	thumbCache map[string][]byte
}

func NewThumbnailer() *Thumbnailer {
	return &Thumbnailer{
		Width:        100,
		Height:       100,
		MaxCacheSize: 10,
		thumbCache:   make(map[string][]byte, 0),
	}
}

func (this *Thumbnailer) RenderFile(absPath string) ([]byte, error) {
	this.cacheMtx.RLock()
	tcache, ok := this.thumbCache[absPath]
	this.cacheMtx.RUnlock()

	if ok {
		return tcache, nil
	}

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

	this.cacheMtx.Lock()
	// FIXME prune old cached thumbnails
	this.thumbCache[absPath] = tcache
	this.cacheMtx.Unlock()

	return tcache, 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")

	}

}