telegram bridge image rotation bug

[Pitbully01]

Matrix → Telegram images rotated 90° counterclockwise

JPEG images sent from Matrix to Telegram are rotated 90° counterclockwise. The same Matrix media is handled correctly by the mautrix-whatsapp and mautrix-signal bridges. Telegram → Matrix also works correctly.

Reproduction

1. Take a portrait photo on a phone.
2. Send it from FluffyChat to a room bridged to Telegram.
3. The image arrives on Telegram rotated 90° counterclockwise.

The problem occurs when sending with compression, without compression, and as a file. A screenshot is transferred with the correct orientation.

Image details

• Uncompressed camera JPEG: physical pixel size 4000×1848, EXIF Orientation 6.
• Its Matrix event reports w: 1848 and h: 4000.
• FluffyChat-compressed JPEG: physical pixel size 1440×3120, EXIF Orientation 0.
• Screenshots are oriented correctly.

The Matrix → Telegram upload path decodes images with Go's image.Decode and re-encodes them as JPEG. image.Decode does not apply EXIF orientation. The issue is still present on main at commit 83554ac2.

Environment

• Bridge: mautrix-telegram v26.08
• Build date: Sun, 16 Aug 2026 13:22:10 UTC
• Docker image: dock.mau.dev/mautrix/telegram:latest
• No relevant image/media errors are logged while sending.

Checklist

• This is an actual bug, not just a setup issue (see the troubleshooting docs or ask in the Matrix room for setup help).