Support matrix
| Format | Extensions | Open | Save | Layers |
|---|---|---|---|---|
| PhotoTux document | .ptx |
Yes | Yes | Yes |
| Photoshop | .psd |
Yes | Yes | Subset |
| PNG | .png |
Yes | Yes | Flattened |
| JPEG | .jpg, .jpeg |
Yes | Yes | Flattened |
| WebP | .webp |
Yes | Yes | Flattened |
| TIFF | .tif, .tiff |
Yes | Yes | Flattened |
| BMP | .bmp |
Yes | Yes | Flattened |
| GIF | .gif |
Yes | Yes | Flattened, first frame |
The export format is chosen by the extension you type in the Save or Export dialog. An extension PhotoTux does not recognise is refused rather than guessed at.
.ptx — the native document
A chunked container holding:
- the layer graph — every layer’s kind, name, opacity, blend mode, visibility, locks, clipping, blend-if ranges, styles and filter plan;
- a raster per raster layer;
- a mask per masked layer;
- the source pixels of every smart object, so a placement can be re-applied rather than re-composed;
- the document’s embedded ICC profile, if it has one.
Layer rasters are stored as PNG inside the container and the whole thing is deflate-compressed.
The format is pre-1.0. The current container version is 2; version 1 documents still open. Newer builds read older documents, but an older build will not read a newer document. While PhotoTux is pre-release, export anything important to PNG or PSD as well.
PSD
PhotoTux reads and writes a deliberate subset:
Carried: RGB colour, 8 bits per channel, layers with names, opacity, visibility and blend modes, and the flattened composite.
Not carried: CMYK, Lab and indexed colour; 16- and 32-bit files; adjustment layers, layer styles, smart objects and text as PSD understands them; layer comps; paths.
On import, everything the subset could not carry is listed in a compatibility report rather than dropped in silence. A report is not an error — the file has opened, and the report says what is different about it.
On export, features with no PSD equivalent are flattened into the layer they belong to.
PSD is an interchange format here, not a working format. Round-tripping a
document through PSD loses adjustment layers and filter plans. Keep the .ptx
as your master.
Flat formats
| Format | Alpha | Compression | Notes |
|---|---|---|---|
| PNG | Yes | Lossless | The safe default for exporting. |
| JPEG | No | Lossy | Written at quality 92 — visually lossless for most images. Transparent areas are composited against the layers below. |
| WebP | Yes | Lossy or lossless | Smaller than PNG at similar quality. |
| TIFF | Yes | Lossless | For handing to print or to other editors. |
| BMP | No | None | Large. Included because some tools still want it. |
| GIF | 1-bit | Lossless, 256 colours | First frame only. PhotoTux is not an animation editor. |
Limits at the file boundary
Every file PhotoTux opens is somebody else’s bytes, so the parsers work behind fixed limits:
| Limit | Value |
|---|---|
| Maximum width or height | 32,768 pixels |
| Maximum decoded RGBA buffer | 512 MB |
A file that exceeds either is refused with a message naming the reason, rather than being loaded until something runs out of memory.
Colour profiles
ICC profiles can be embedded in a document, assigned to it without changing its numbers, or converted to so the appearance is preserved across spaces. sRGB and Display-P3 are built in, and an arbitrary profile can be embedded from a file.
Profile bytes are validated before they are written into a document, so a
truncated or malformed .icc is rejected at the point you choose it rather
than at the point something tries to use it.
Soft-proofing shows what a document will look like through a chosen output profile without changing the document.
Recovery files
Documents open when a session ends badly are written to a recovery store and offered back at the next launch. They are not a format you open by hand — see opening, saving and exporting.