Resize favicons before storing them

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/prometheus/client_golang v1.20.5
 	github.com/tdewolff/minify/v2 v2.21.2
 	golang.org/x/crypto v0.31.0
+	golang.org/x/image v0.23.0
 	golang.org/x/net v0.32.0
 	golang.org/x/oauth2 v0.24.0
 	golang.org/x/term v0.27.0

go.sum

@@ -70,6 +70,8 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.31.0 h1:ihbySMvVjLAeSH1IbfcRTkD/iNscyz8rGzjF/E5hV6U=
 golang.org/x/crypto v0.31.0/go.mod h1:kDsLvtWBEx7MV9tJOj9bnXsPbxwJQ6csT/x4KIN4Ssk=
+golang.org/x/image v0.23.0 h1:HseQ7c2OpPKTPVzNjG5fwJsOTCiiwS4QdsYi5XU6H68=
+golang.org/x/image v0.23.0/go.mod h1:wJJBTdLfCCf3tiHa1fNxpZmUI4mmoZvwMCPP0ddoNKY=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=

internal/reader/icon/finder.go

@@ -4,12 +4,18 @@
 package icon // import "miniflux.app/v2/internal/reader/icon"
 
 import (
+	"bytes"
 	"encoding/base64"
 	"fmt"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
 	"io"
 	"log/slog"
 	"net/url"
 	"regexp"
+	"slices"
 	"strings"
 
 	"miniflux.app/v2/internal/config"
@@ -19,6 +25,7 @@ import (
 	"miniflux.app/v2/internal/urllib"
 
 	"github.com/PuerkitoBio/goquery"
+	"golang.org/x/image/draw"
 	"golang.org/x/net/html/charset"
 )
 
@@ -180,9 +187,59 @@ func (f *IconFinder) DownloadIcon(iconURL string) (*model.Icon, error) {
 		Content:  responseBody,
 	}
 
+	icon = resizeIcon(icon)
+
 	return icon, nil
 }
 
+func resizeIcon(icon *model.Icon) *model.Icon {
+	r := bytes.NewReader(icon.Content)
+
+	if !slices.Contains([]string{"image/jpeg", "image/png", "image/gif"}, icon.MimeType) {
+		slog.Info("icon isn't a png/gif/jpeg/ico, can't resize", slog.String("mimetype", icon.MimeType))
+		return icon
+	}
+
+	// Don't resize icons that we can't decode, or that already have the right size.
+	config, _, err := image.DecodeConfig(r)
+	if err != nil {
+		slog.Warn("unable to decode the metadata of the icon", slog.Any("error", err))
+		return icon
+	}
+	if config.Height <= 16 && config.Width <= 16 {
+		slog.Debug("icon don't need to be rescaled", slog.Int("height", config.Height), slog.Int("width", config.Width))
+		return icon
+	}
+
+	r.Seek(0, io.SeekStart)
+
+	var src image.Image
+	switch icon.MimeType {
+	case "image/jpeg":
+		src, err = jpeg.Decode(r)
+	case "image/png":
+		src, err = png.Decode(r)
+	case "image/gif":
+		src, err = gif.Decode(r)
+	}
+	if err != nil {
+		slog.Warn("unable to decode the icon", slog.Any("error", err))
+		return icon
+	}
+
+	dst := image.NewRGBA(image.Rect(0, 0, 16, 16))
+	draw.BiLinear.Scale(dst, dst.Rect, src, src.Bounds(), draw.Over, nil)
+
+	var b bytes.Buffer
+	if err = png.Encode(io.Writer(&b), dst); err != nil {
+		slog.Warn("unable to encode the new icon", slog.Any("error", err))
+	}
+
+	icon.Content = b.Bytes()
+	icon.MimeType = "image/png"
+	return icon
+}
+
 func findIconURLsFromHTMLDocument(body io.Reader, contentType string) ([]string, error) {
 	queries := []string{
 		"link[rel='icon' i]",

internal/reader/icon/finder_test.go

@@ -4,8 +4,13 @@
 package icon // import "miniflux.app/v2/internal/reader/icon"
 
 import (
+	"bytes"
+	"encoding/base64"
+	"image"
 	"strings"
 	"testing"
+
+	"miniflux.app/v2/internal/model"
 )
 
 func TestParseImageDataURL(t *testing.T) {
@@ -125,3 +130,52 @@ func TestParseDocumentWithWhitespaceIconURL(t *testing.T) {
 		t.Errorf(`Invalid icon URL, got %q`, iconURLs[0])
 	}
 }
+
+func TestResizeIconSmallGif(t *testing.T) {
+	data, err := base64.StdEncoding.DecodeString("R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==")
+	if err != nil {
+		t.Fatal(err)
+	}
+	icon := model.Icon{
+		Content:  data,
+		MimeType: "image/gif",
+	}
+	if !bytes.Equal(icon.Content, resizeIcon(&icon).Content) {
+		t.Fatalf("Converted gif smaller than 16x16")
+	}
+}
+
+func TestResizeIconPng(t *testing.T) {
+	data, err := base64.StdEncoding.DecodeString("iVBORw0KGgoAAAANSUhEUgAAABEAAAARCAYAAAA7bUf6AAAAHElEQVR42mP8z/C/noFCwDhqyKgho4aMGkIlQwBrHSpf28Yx+gAAAABJRU5ErkJggg==")
+	if err != nil {
+		t.Fatal(err)
+	}
+	icon := model.Icon{
+		Content:  data,
+		MimeType: "image/png",
+	}
+	resizedIcon := resizeIcon(&icon)
+
+	if bytes.Equal(data, resizedIcon.Content) {
+		t.Fatalf("Didn't convert png of 17x17")
+	}
+
+	config, _, err := image.DecodeConfig(bytes.NewReader(resizedIcon.Content))
+	if err != nil {
+		t.Fatalf("Couln't decode resulting png: %v", err)
+	}
+
+	if config.Height != 16 || config.Width != 16 {
+		t.Fatalf("Was expecting an image of 16x16, got %dx%d", config.Width, config.Height)
+	}
+}
+
+func TestResizeInvalidImage(t *testing.T) {
+	icon := model.Icon{
+		Content:  []byte("invalid data"),
+		MimeType: "image/gif",
+	}
+	if !bytes.Equal(icon.Content, resizeIcon(&icon).Content) {
+		t.Fatalf("Tried to convert an invalid image")
+	}
+}