navidrome/core/artwork.go

package core

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"image"
	_ "image/gif"
	"image/jpeg"
	"image/png"
	"io"
	"os"
	"path/filepath"
	"strings"

	"github.com/dhowden/tag"
	"github.com/disintegration/imaging"
	"github.com/navidrome/navidrome/conf"
	"github.com/navidrome/navidrome/consts"
	"github.com/navidrome/navidrome/log"
	"github.com/navidrome/navidrome/model"
	"github.com/navidrome/navidrome/resources"
	_ "golang.org/x/image/webp"
)

type Artwork interface {
	Get(ctx context.Context, id string, size int) (io.ReadCloser, error)
}

func NewArtwork(ds model.DataStore) Artwork {
	return &artwork{ds: ds}
}

type artwork struct {
	ds model.DataStore
}

func (a *artwork) Get(ctx context.Context, id string, size int) (io.ReadCloser, error) {
	r, _, err := a.get(ctx, id, size)
	return r, err
}

func (a *artwork) get(ctx context.Context, id string, size int) (reader io.ReadCloser, path string, err error) {
	artId, err := model.ParseArtworkID(id)
	if err != nil {
		return nil, "", errors.New("invalid ID")
	}

	// If requested a resized
	if size > 0 {
		return a.resizedFromOriginal(ctx, id, size)
	}

	id = artId.ID
	al, err := a.ds.Album(ctx).Get(id)
	if errors.Is(err, model.ErrNotFound) {
		r, path := fromPlaceholder()()
		return r, path, nil
	}
	if err != nil {
		return nil, "", err
	}

	r, path := extractImage(ctx, artId,
		fromExternalFile(al.ImageFiles, "cover.png", "cover.jpg", "cover.jpeg", "cover.webp"),
		fromExternalFile(al.ImageFiles, "folder.png", "folder.jpg", "folder.jpeg", "folder.webp"),
		fromExternalFile(al.ImageFiles, "album.png", "album.jpg", "album.jpeg", "album.webp"),
		fromExternalFile(al.ImageFiles, "albumart.png", "albumart.jpg", "albumart.jpeg", "albumart.webp"),
		fromExternalFile(al.ImageFiles, "front.png", "front.jpg", "front.jpeg", "front.webp"),
		fromTag(al.EmbedArtPath),
		fromPlaceholder(),
	)
	return r, path, nil
}

func (a *artwork) resizedFromOriginal(ctx context.Context, id string, size int) (io.ReadCloser, string, error) {
	r, path, err := a.get(ctx, id, 0)
	if err != nil || r == nil {
		return nil, "", err
	}
	defer r.Close()
	usePng := strings.ToLower(filepath.Ext(path)) == ".png"
	r, err = resizeImage(r, size, usePng)
	if err != nil {
		r, path := fromPlaceholder()()
		return r, path, err
	}
	return r, fmt.Sprintf("%s@%d", path, size), nil
}

func extractImage(ctx context.Context, artId model.ArtworkID, extractFuncs ...func() (io.ReadCloser, string)) (io.ReadCloser, string) {
	for _, f := range extractFuncs {
		r, path := f()
		if r != nil {
			log.Trace(ctx, "Found artwork", "artId", artId, "path", path)
			return r, path
		}
	}
	log.Error(ctx, "extractImage should never reach this point!", "artId", artId, "path")
	return nil, ""
}

// This seems unoptimized, but we need to make sure the priority order of validNames
// is preserved (i.e. png is better than jpg)
func fromExternalFile(files string, validNames ...string) func() (io.ReadCloser, string) {
	return func() (io.ReadCloser, string) {
		fileList := filepath.SplitList(files)
		for _, validName := range validNames {
			for _, file := range fileList {
				_, name := filepath.Split(file)
				if !strings.EqualFold(validName, name) {
					continue
				}
				f, err := os.Open(file)
				if err != nil {
					continue
				}
				return f, file
			}
		}
		return nil, ""
	}
}

func fromTag(path string) func() (io.ReadCloser, string) {
	return func() (io.ReadCloser, string) {
		if path == "" {
			return nil, ""
		}
		f, err := os.Open(path)
		if err != nil {
			return nil, ""
		}
		defer f.Close()

		m, err := tag.ReadFrom(f)
		if err != nil {
			return nil, ""
		}

		picture := m.Picture()
		if picture == nil {
			return nil, ""
		}
		return io.NopCloser(bytes.NewReader(picture.Data)), path
	}
}

func fromPlaceholder() func() (io.ReadCloser, string) {
	return func() (io.ReadCloser, string) {
		r, _ := resources.FS().Open(consts.PlaceholderAlbumArt)
		return r, consts.PlaceholderAlbumArt
	}
}

func resizeImage(reader io.Reader, size int, usePng bool) (io.ReadCloser, error) {
	img, _, err := image.Decode(reader)
	if err != nil {
		return nil, err
	}

	// Preserve the aspect ratio of the image.
	var m *image.NRGBA
	bounds := img.Bounds()
	if bounds.Max.X > bounds.Max.Y {
		m = imaging.Resize(img, size, 0, imaging.Lanczos)
	} else {
		m = imaging.Resize(img, 0, size, imaging.Lanczos)
	}

	buf := new(bytes.Buffer)
	if usePng {
		err = png.Encode(buf, m)
	} else {
		err = jpeg.Encode(buf, m, &jpeg.Options{Quality: conf.Server.CoverJpegQuality})
	}
	return io.NopCloser(buf), err
}