Image preview
Image preview displays images in the preview area, with zoom and rotation controls. Some formats use system thumbnails or plugin-provided images.
Supported formats
| Format | Extensions |
|---|---|
| PNG | .png |
| JPEG | .jpg, .jpeg |
| GIF | .gif (first frame only, animation is not played) |
| BMP | .bmp |
| WebP | .webp |
| TIFF | .tif, .tiff (multi-page files show the first page) |
| SVG | .svg, .svgz, drawn as an image rather than as source |
| Icons | .ico (the largest frame in the container is picked automatically) |
This is also the range used for list thumbnails and folder peek images — if it can be previewed, it gets a thumbnail.
Cover art and system thumbnails
Two kinds of file are not images themselves, yet still have something to show in the preview area and in thumbnails:
| File | Where the image comes from |
|---|---|
Audio: .mp3, .flac, .m4a, .m4b | The cover art embedded in the file. When several images are stored in one file, the one marked as the front cover wins; otherwise the first one is used |
Everything else: .psd, .ai, .dwg, video, camera RAW… | A thumbnail asked of Windows. Anything that has a thumbnail in File Explorer has one here — the very same image |
The second kind exists on Windows only, because those images are produced by the software that handles the format (Photoshop, AutoCAD and so on); without it installed there is nothing to fetch. macOS and Linux have no equivalent, and those files show a file icon there.
Zoom and rotate
| Action | How |
|---|---|
| Zoom in / Zoom out | Click the matching button on the preview |
| Move around after zooming | Drag on the image |
| Rotate left / Rotate right | Click the matching button; only the preview turns |
Zooming and rotating are never written back to the file. Move to another file and back and the orientation is as it was — tessoa does not touch your photos.
Which images are not shown
These fall back to a file icon on purpose, not because something went wrong:
- HEIC: no built-in decoder. A Windows system thumbnail or installed plugin may provide an image; otherwise the file icon is shown.
- Images with too many pixels: past 128 megapixels of width × height tessoa falls back to an icon.
Once it is settled that there is nothing to show, a line reading No preview for this file type appears under the icon. It is not written while decoding is still going on, because the answer isn't in yet.