media: convert png and jpeg stickers to webp without ffmpeg

pkg/connector/capabilities.go

@@ -115,6 +115,9 @@ var fileCaps = event.FileFeatureMap{
 	event.CapMsgSticker: {
 		MimeTypes: map[string]event.CapabilitySupportLevel{
 			"image/webp": event.CapLevelFullySupported,
+			// These are converted to webp
+			"image/jpeg": event.CapLevelPartialSupport,
+			"image/png":  event.CapLevelPartialSupport,
 			// TODO
 			//"video/lottie+json": event.CapLevelFullySupported,
 			//"video/webm": event.CapLevelFullySupported,

pkg/connector/matrix.go

@@ -38,6 +38,7 @@ import (
 	"github.com/rs/zerolog"
 	"go.mau.fi/util/ffmpeg"
 	"go.mau.fi/util/variationselector"
+	"go.mau.fi/webp"
 	"maunium.net/go/mautrix/bridgev2"
 	"maunium.net/go/mautrix/bridgev2/database"
 	"maunium.net/go/mautrix/bridgev2/networkid"
@@ -75,7 +76,23 @@ func (t *TelegramClient) transferMediaToTelegram(ctx context.Context, content *e
 	filename := getMediaFilename(content)
 	err := t.main.Bridge.Bot.DownloadMediaToFile(ctx, content.URL, content.File, false, func(f *os.File) (err error) {
 		uploadFilename := f.Name()
-		if sticker && content.Info != nil && (content.Info.MimeType != "video/webm" && content.Info.MimeType != "application/x-tgsticker") {
+		if sticker && content.Info != nil && (content.Info.MimeType == "image/png" || content.Info.MimeType == "image/jpeg") {
+			tempFile, err := os.CreateTemp("", "telegram-sticker-*")
+			if err != nil {
+				return err
+			}
+			defer func() {
+				tempFile.Close()
+				os.Remove(tempFile.Name())
+			}()
+			if image, _, err := image.Decode(f); err != nil {
+				return fmt.Errorf("failed to decode sticker image: %w", err)
+			} else if err := webp.Encode(tempFile, image, nil); err != nil {
+				return fmt.Errorf("failed to encode sticker webp image: %w", err)
+			}
+			uploadFilename = tempFile.Name()
+			content.Info.MimeType = "image/webp"
+		} else if sticker && content.Info != nil && (content.Info.MimeType != "video/webm" && content.Info.MimeType != "application/x-tgsticker") {
 			uploadFilename, err = ffmpeg.ConvertPath(ctx, uploadFilename, ".webp", []string{}, []string{}, false)
 			if err != nil {
 				return fmt.Errorf("failed to convert sticker to webm: %+w", err)