PhotoTux has two ways of changing how an image looks, and the difference matters.

  • An adjustment layer sits in the stack and changes everything below it. Nothing under it is modified; hide the adjustment and the original is back.
  • A filter is attached to one layer as an entry in that layer’s filter plan. It is re-editable and reorderable, and the layer’s own pixels are left alone until you flatten or rasterize.

Neither is destructive while the document is open in .ptx form. Both become permanent when you flatten or export.

Adjustment layers

Layer ▸ New Adjustment Layer offers ten:

Adjustment What it does
Brightness/Contrast The two blunt controls. Good for a quick lift.
Levels Black point, white point and gamma. The right tool for setting the ends of the tonal range.
Exposure Scales linear light, the way a stop of exposure does on a camera.
Hue/Saturation Rotates hue, and scales saturation and lightness.
Vibrance Saturation that leans on the muted colours and leaves the already-saturated ones alone.
Black & White A controllable monochrome conversion, rather than dropping saturation to zero.
White Balance Corrects a colour cast by naming what should have been neutral.
Threshold Everything above a level becomes white, everything below it black.
Posterize Reduces the number of levels per channel.
Invert Inverts the composite below. No parameters.

Each arrives as a layer with an A badge, and its controls appear in the Properties panel. Change them at any point; the change is a history step like any other.

To adjust one layer rather than everything below it, put the adjustment directly above the layer and use Layer ▸ Create Clipping Mask. The adjustment then applies only to the layer it is clipped to.

The order of adjustments matters

Adjustments compose bottom to top, so a Levels under a Hue/Saturation is a different picture from a Hue/Saturation under a Levels. Drag them in the Layers panel to reorder.

Filters

Filter in the menu bar lists thirteen effects, and each is also reachable from the gallery.

Filter What it does
Gaussian Blur The standard soft blur. One radius.
Box Blur A cheaper blur with a squarer falloff.
Motion Blur Blur along an angle, as if the camera moved.
Zoom Blur Blur radiating from a centre point.
Sharpen Increases local contrast at edges.
Unsharp Mask Sharpening with amount, radius and threshold, so you can sharpen edges without amplifying noise.
High Pass Keeps only the fine detail, discarding the broad tones. Used with Overlay or Soft Light for sharpening.
Clarity Midtone local contrast.
Denoise Reduces sensor noise.
Emboss Turns edges into a raised relief.
Add Noise Adds grain, for matching a noisy plate or breaking up banding.
Offset Shifts pixels, wrapping at the edges. Used for making a texture tile.
Invert Inverts this layer’s pixels — as a filter rather than an adjustment layer.

Filter ▸ Filter Gallery opens a preview that draws on the canvas without touching the document.

The Filter Gallery dialog over a dimmed canvas, with Gaussian Blur selected, a Radius slider, and Preview, Apply and Cancel buttons.

  1. Pick an effect from the list.
  2. Move its sliders — the canvas updates live.
  3. Preview refreshes if you have changed the document underneath.
  4. Apply commits it into the layer’s filter plan as one undo step.
  5. Cancel throws it away and leaves the document exactly as it was.

While the gallery is open, the document is not marked as changed. Nothing is committed until you press Apply, and a preview that has gone stale — because the layer stack moved while the dialog was open — is refused rather than applied to the wrong thing.

The filter plan

Every layer carries an ordered list of the filters applied to it. From the Properties panel you can:

  • Reorder them — a blur before a sharpen is not the same picture as a sharpen before a blur.
  • Disable one without removing it, to compare.
  • Edit its parameters at any time.
  • Remove one.

The plan is stored in the .ptx document, so it survives a save and reopen. Exporting to PNG or JPEG flattens it, as does Flatten Image.

Colour management

Colour handling lives under Image ▸ Color:

  • Assign Profile tags the document as being in a colour space, without changing any numbers.
  • Convert to changes the numbers so the image looks the same in the new space.
  • Soft-Proof shows what the document will look like through a chosen output profile, without changing it.
  • Embed ICC Profile… writes a profile file into the document, and Clear Embedded ICC removes it.

sRGB and Display-P3 are built in. Profile bytes are validated before they are embedded, so a corrupt file is refused rather than written into your document.