Support sending heic images

Implements feature request mautrix#635 by converting heic files
to jpeg before attaching to a message

go.mod

@@ -27,6 +27,7 @@ require (
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/coreos/go-systemd/v22 v22.5.0 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/jdeng/goheif v0.0.0-20200323230657-a0d6a8b3e68f // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/mattn/go-colorable v0.1.12 // indirect
 	github.com/mattn/go-isatty v0.0.14 // indirect

go.sum

@@ -23,6 +23,8 @@ github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
 github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=
 github.com/gorilla/websocket v1.5.0 h1:PPwGk2jz7EePpoHN/+ClbZu8SPxiqlu12wZP/3sWmnc=
 github.com/gorilla/websocket v1.5.0/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/jdeng/goheif v0.0.0-20200323230657-a0d6a8b3e68f h1:jYkcRYsnnvPF07yn4XJx3k8duM4KDw3QYB3p8bUrk80=
+github.com/jdeng/goheif v0.0.0-20200323230657-a0d6a8b3e68f/go.mod h1:G7IyA3/eR9IFmUIPdyP3c0l4ZaqEvXAk876WfaQ8plc=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=

portal.go

@@ -42,6 +42,7 @@ import (
 	"time"
 
 	"github.com/chai2010/webp"
+	"github.com/jdeng/goheif"
 	"github.com/rs/zerolog"
 	"github.com/tidwall/gjson"
 	"golang.org/x/exp/slices"
@@ -3377,6 +3378,23 @@ func (portal *Portal) downloadThumbnail(ctx context.Context, original []byte, th
 	return createThumbnail(original, png)
 }
 
+func (portal *Portal) convertHEICtoJPEG(heicImage []byte) ([]byte, error) {
+
+
+	heicEncoded, err := goheif.Decode(bytes.NewReader(heicImage))
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode heic image: %w", err)
+	}
+
+	var jpgBuffer bytes.Buffer
+
+	if err = jpeg.Encode(&jpgBuffer, heicEncoded, nil); err != nil {
+		return nil, fmt.Errorf("failed to encode jpeg image: %w", err)
+	}
+
+	return jpgBuffer.Bytes(), nil
+}
+
 func (portal *Portal) convertWebPtoPNG(webpImage []byte) ([]byte, error) {
 	webpDecoded, err := webp.Decode(bytes.NewReader(webpImage))
 	if err != nil {
@@ -3507,6 +3525,9 @@ func (portal *Portal) preprocessMatrixMedia(ctx context.Context, sender *User, r
 		case "image/webp":
 			data, convertErr = portal.convertWebPtoPNG(data)
 			content.Info.MimeType = "image/png"
+		case "image/heic":
+			data, convertErr = portal.convertHEICtoJPEG(data)
+			content.Info.MimeType = "image/jpeg"
 		default:
 			return nil, fmt.Errorf("%w %q in image message", errMediaUnsupportedType, mimeType)
 		}