feat(thumbnails): optional libvips based thumbnail generation

Can be enabled by setting the 'enable_vips' tag on 'go build'

services/thumbnails/pkg/thumbnail/encoding_vips.go

@@ -0,0 +1,66 @@
+//go:build enable_vips
+
+package thumbnail
+
+import (
+	"io"
+
+	"github.com/davidbyttow/govips/v2/vips"
+	"github.com/owncloud/ocis/v2/services/thumbnails/pkg/errors"
+)
+
+// PngEncoder encodes to png
+type PngEncoder struct{}
+
+// Encode encodes to png format
+func (e PngEncoder) Encode(w io.Writer, img interface{}) error {
+	m, ok := img.(*vips.ImageRef)
+	if !ok {
+		return errors.ErrInvalidType
+	}
+
+	buf, _, err := m.ExportPng(vips.NewPngExportParams())
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(buf)
+	return err
+}
+
+// Types returns the png suffix
+func (e PngEncoder) Types() []string {
+	return []string{typePng}
+}
+
+// MimeType returns the mimetype for png files.
+func (e PngEncoder) MimeType() string {
+	return "image/png"
+}
+
+// JpegEncoder encodes to jpg
+type JpegEncoder struct{}
+
+// Encode encodes to jpg
+func (e JpegEncoder) Encode(w io.Writer, img interface{}) error {
+	m, ok := img.(*vips.ImageRef)
+	if !ok {
+		return errors.ErrInvalidType
+	}
+
+	buf, _, err := m.ExportJpeg(vips.NewJpegExportParams())
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(buf)
+	return err
+}
+
+// Types returns the jpg suffixes.
+func (e JpegEncoder) Types() []string {
+	return []string{typeJpeg, typeJpg}
+}
+
+// MimeType returns the mimetype for jpg files.
+func (e JpegEncoder) MimeType() string {
+	return "image/jpeg"
+}