feat(backgrounds): resize images to a maximum of 4K

Resolves https://kolaente.dev/vikunja/vikunja/issues/1373#issuecomment-43491

pkg/modules/background/background.go

@@ -32,6 +32,8 @@ type Image struct {
 	Info interface{} `json:"info,omitempty"`
 }
 
+const MaxBackgroundImageHeight = 3840
+
 // Provider represents something that is able to get a project of images and set one of them as background
 type Provider interface {
 	// Search is used to either return a pre-defined project of Image or let the user search for an image

pkg/modules/background/handler/background.go

@@ -17,10 +17,13 @@
 package handler
 
 import (
+	"bytes"
 	_ "image/gif"  // To make sure the decoder used for generating blurHashes recognizes gifs
 	_ "image/jpeg" // To make sure the decoder used for generating blurHashes recognizes jpgs
 	_ "image/png"  // To make sure the decoder used for generating blurHashes recognizes pngs
 
+	"github.com/disintegration/imaging"
+
 	_ "golang.org/x/image/bmp"  // To make sure the decoder used for generating blurHashes recognizes bmps
 	_ "golang.org/x/image/tiff" // To make sure the decoder used for generating blurHashes recognizes tiffs
 	_ "golang.org/x/image/webp" // To make sure the decoder used for generating blurHashes recognizes tiffs
@@ -220,7 +223,30 @@ func (bp *BackgroundProvider) UploadBackground(c echo.Context) error {
 
 func SaveBackgroundFile(s *xorm.Session, auth web.Auth, project *models.Project, srcf io.ReadSeeker, filename string, filesize uint64) (err error) {
 	_, _ = srcf.Seek(0, io.SeekStart)
-	f, err := files.Create(srcf, filename, filesize, auth)
+	src, err := imaging.Decode(srcf)
+	if err != nil {
+		return err
+	}
+
+	_, _ = srcf.Seek(0, io.SeekStart)
+	imgConfig, _, err := image.DecodeConfig(srcf)
+	if err != nil {
+		return err
+	}
+
+	height := imgConfig.Height
+	if imgConfig.Height > background.MaxBackgroundImageHeight {
+		height = background.MaxBackgroundImageHeight
+	}
+
+	buf := bytes.Buffer{}
+	dst := imaging.Resize(src, 0, height, imaging.Lanczos)
+	err = imaging.Encode(&buf, dst, imaging.JPEG, imaging.JPEGQuality(80))
+	if err != nil {
+		return err
+	}
+
+	f, err := files.Create(&buf, filename, filesize, auth)
 	if err != nil {
 		return err
 	}

pkg/modules/background/unsplash/unsplash.go

@@ -256,7 +256,7 @@ func (p *Provider) Set(s *xorm.Session, image *background.Image, project *models
 
 	// Download the photo from unsplash
 	// The parameters crop the image to a max width of 2560 and a max height of 2048 to save bandwidth and storage.
-	req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, photo.Urls.Raw+"&w=2560&h=2048&q=90", nil)
+	req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, photo.Urls.Raw+"&fm=jpg&h="+strconv.FormatInt(background.MaxBackgroundImageHeight, 10)+"&q=80", nil)
 	if err != nil {
 		return
 	}