Attachment viewer can't zoom in enough for some images

**Describe the bug**
I needed to download the image and open it in the gallery to be able to zoom in enough to read the text.

**To Reproduce**
Steps to reproduce the behavior:
1. Receive a 1080x7600px image
2. Tap on the image
3. Zoom in to maximum
4. Can't make the image fill the full width or zoom in even more to read small text on it.

**Expected behavior**
Let's you zoom in more. (My default gallery app allows me to)

**Smartphone (please complete the following information):**
- Device: Nexus 5X
- OS: Android 8.1

**Additional context**
- App version and store 1.0.5-F
- Homeserver: bubu1.eu

(Can't share the original image or screenshots of it. Tried to recreate one of the same dimensions with gimp but gave up after 10 minutes of failing :see_no_evil: )