feature(thumbnails): add the ability to define custom image processors

changelog/unreleased/thumbnail-processors.md

@@ -0,0 +1,19 @@
+Enhancement: Thumbnail generation with image processors
+
+Thumbnails can now be changed during creation, previously the images were always scaled to fit the given frame,
+but it could happen that the images were cut off because they could not be placed better due to the aspect ratio.
+
+This pr introduces the possibility of specifying how the behavior should be, following processors are available
+
+* resize
+* fit
+* fill
+* thumbnail
+
+the processor can be applied by adding the processor query param to the request, e.g. `processor=fit`, `processor=fill`, ...
+
+to find out more how the individual processors work please read https://github.com/disintegration/imaging
+
+if no processor is provided it behaves the same as before (resize for gif's and thumbnail for all other)
+
+https://github.com/owncloud/ocis/pull/6992

protogen/proto/ocis/services/thumbnails/v0/thumbnails.proto

@@ -47,9 +47,11 @@ message GetThumbnailRequest {
     int32 width = 3;
     // The height of the thumbnail
     int32 height = 4;
+    // Indicates which image processor to use
+    string processor = 5;
     oneof source {
-      ocis.messages.thumbnails.v0.WebdavSource webdav_source = 5;
-      ocis.messages.thumbnails.v0.CS3Source cs3_source = 6;
+      ocis.messages.thumbnails.v0.WebdavSource webdav_source = 6;
+      ocis.messages.thumbnails.v0.CS3Source cs3_source = 7;
     }
 }
 

services/thumbnails/pkg/service/grpc/v0/service.go

@@ -16,16 +16,17 @@ import (
 	"github.com/cs3org/reva/v2/pkg/storagespace"
 	"github.com/cs3org/reva/v2/pkg/utils"
 	"github.com/golang-jwt/jwt/v4"
+	"github.com/pkg/errors"
+	merrors "go-micro.dev/v4/errors"
+	"google.golang.org/grpc/metadata"
+
 	"github.com/owncloud/ocis/v2/ocis-pkg/log"
 	thumbnailssvc "github.com/owncloud/ocis/v2/protogen/gen/ocis/services/thumbnails/v0"
 	"github.com/owncloud/ocis/v2/services/thumbnails/pkg/preprocessor"
 	"github.com/owncloud/ocis/v2/services/thumbnails/pkg/service/grpc/v0/decorators"
 	tjwt "github.com/owncloud/ocis/v2/services/thumbnails/pkg/service/jwt"
 	"github.com/owncloud/ocis/v2/services/thumbnails/pkg/thumbnail"
 	"github.com/owncloud/ocis/v2/services/thumbnails/pkg/thumbnail/imgsource"
-	"github.com/pkg/errors"
-	merrors "go-micro.dev/v4/errors"
-	"google.golang.org/grpc/metadata"
 )
 
 // NewService returns a service implementation for Service.
@@ -124,7 +125,7 @@ func (g Thumbnail) handleCS3Source(ctx context.Context, req *thumbnailssvc.GetTh
 	if tType == "" {
 		tType = req.GetThumbnailType().String()
 	}
-	tr, err := thumbnail.PrepareRequest(int(req.Width), int(req.Height), tType, sRes.GetInfo().GetChecksum().GetSum())
+	tr, err := thumbnail.PrepareRequest(int(req.Width), int(req.Height), tType, sRes.GetInfo().GetChecksum().GetSum(), req.Processor)
 	if err != nil {
 		return "", merrors.BadRequest(g.serviceID, err.Error())
 	}
@@ -207,7 +208,7 @@ func (g Thumbnail) handleWebdavSource(ctx context.Context, req *thumbnailssvc.Ge
 	if tType == "" {
 		tType = req.GetThumbnailType().String()
 	}
-	tr, err := thumbnail.PrepareRequest(int(req.Width), int(req.Height), tType, sRes.GetInfo().GetChecksum().GetSum())
+	tr, err := thumbnail.PrepareRequest(int(req.Width), int(req.Height), tType, sRes.GetInfo().GetChecksum().GetSum(), req.Processor)
 	if err != nil {
 		return "", merrors.BadRequest(g.serviceID, err.Error())
 	}

services/thumbnails/pkg/thumbnail/encoding.go

@@ -114,8 +114,8 @@ func EncoderForType(fileType string) (Encoder, error) {
 }
 
 // GetExtForMime return the supported extension by mime
-func GetExtForMime(mime string) string {
-	ext := strings.TrimPrefix(strings.TrimSpace(strings.ToLower(mime)), "image/")
+func GetExtForMime(fileType string) string {
+	ext := strings.TrimPrefix(strings.TrimSpace(strings.ToLower(fileType)), "image/")
 	switch ext {
 	case typeJpg, typeJpeg, typePng, typeGif:
 		return ext

services/thumbnails/pkg/thumbnail/generator.go

@@ -14,28 +14,26 @@ import (
 var (
 	// ErrInvalidType represents the error when a type can't be encoded.
 	ErrInvalidType2 = errors.New("can't encode this type")
-	// ErrNoGeneratorForType represents the error when no generator could be found for a type.
-	ErrNoGeneratorForType = errors.New("no generator for this type found")
 )
 
 type Generator interface {
-	GenerateThumbnail(image.Rectangle, interface{}) (interface{}, error)
+	Generate(image.Rectangle, interface{}, Processor) (interface{}, error)
 }
 
 type SimpleGenerator struct{}
 
-func (g SimpleGenerator) GenerateThumbnail(size image.Rectangle, img interface{}) (interface{}, error) {
+func (g SimpleGenerator) Generate(size image.Rectangle, img interface{}, processor Processor) (interface{}, error) {
 	m, ok := img.(image.Image)
 	if !ok {
 		return nil, ErrInvalidType2
 	}
 
-	return imaging.Thumbnail(m, size.Dx(), size.Dy(), imaging.Lanczos), nil
+	return processor.Process(m, size.Dx(), size.Dy(), imaging.Lanczos), nil
 }
 
 type GifGenerator struct{}
 
-func (g GifGenerator) GenerateThumbnail(size image.Rectangle, img interface{}) (interface{}, error) {
+func (g GifGenerator) Generate(size image.Rectangle, img interface{}, processor Processor) (interface{}, error) {
 	// Code inspired by https://github.com/willnorris/gifresize/blob/db93a7e1dcb1c279f7eeb99cc6d90b9e2e23e871/gifresize.go
 
 	m, ok := img.(*gif.GIF)
@@ -51,8 +49,8 @@ func (g GifGenerator) GenerateThumbnail(size image.Rectangle, img interface{}) (
 		bounds := frame.Bounds()
 		prev := tmp
 		draw.Draw(tmp, bounds, frame, bounds.Min, draw.Over)
-		scaled := imaging.Resize(tmp, size.Dx(), size.Dy(), imaging.Lanczos)
-		m.Image[i] = g.imageToPaletted(scaled, frame.Palette)
+		processed := processor.Process(tmp, size.Dx(), size.Dy(), imaging.Lanczos)
+		m.Image[i] = g.imageToPaletted(processed, frame.Palette)
 
 		switch m.Disposal[i] {
 		case gif.DisposalBackground:

services/thumbnails/pkg/thumbnail/processor.go

@@ -0,0 +1,51 @@
+package thumbnail
+
+import (
+	"image"
+	"strings"
+
+	"github.com/disintegration/imaging"
+)
+
+// Processor processes the thumbnail by applying different transformations to it.
+type Processor interface {
+	ID() string
+	Process(img image.Image, width, height int, filter imaging.ResampleFilter) *image.NRGBA
+}
+
+// DefinableProcessor is the most simple processor, it holds a replaceable image converter function.
+type DefinableProcessor struct {
+	Slug      string
+	Converter func(img image.Image, width, height int, filter imaging.ResampleFilter) *image.NRGBA
+}
+
+// ID returns the processor identification.
+func (p DefinableProcessor) ID() string { return p.Slug }
+
+// Process transforms the given image.
+func (p DefinableProcessor) Process(img image.Image, width, height int, filter imaging.ResampleFilter) *image.NRGBA {
+	return p.Converter(img, width, height, filter)
+}
+
+// ProcessorFor returns a matching Processor
+func ProcessorFor(id, fileType string) (Processor, error) {
+	switch strings.ToLower(id) {
+	case "fit":
+		return DefinableProcessor{Slug: strings.ToLower(id), Converter: imaging.Fit}, nil
+	case "resize":
+		return DefinableProcessor{Slug: strings.ToLower(id), Converter: imaging.Resize}, nil
+	case "fill":
+		return DefinableProcessor{Slug: strings.ToLower(id), Converter: func(img image.Image, width, height int, filter imaging.ResampleFilter) *image.NRGBA {
+			return imaging.Fill(img, width, height, imaging.Center, filter)
+		}}, nil
+	case "thumbnail":
+		return DefinableProcessor{Slug: strings.ToLower(id), Converter: imaging.Thumbnail}, nil
+	default:
+		switch strings.ToLower(fileType) {
+		case typeGif:
+			return DefinableProcessor{Converter: imaging.Resize}, nil
+		default:
+			return DefinableProcessor{Converter: imaging.Thumbnail}, nil
+		}
+	}
+}