To apply an effect to only part of an image, add the effect to the image, then use a mask to define where the treatment appears. A circular mask can confine a halftone to one area while the rest of the picture keeps its original appearance. Soften the edge for a gradual transition, or keep it sharp for a graphic cutout.

This guide uses Artfkt for Mac and Windows, which runs on Apple Silicon Macs with macOS 13 or later and 64-bit Windows 10 or 11 PCs. Mask authoring is a desktop feature; the free browser demo lets you explore effects and export an image, but does not let you create these masks.

The cover is a conceptual diagram, not an Artfkt render. Below, we’ll walk through the controls and a real example so you can choose the right kind of mask for your own picture.

Choose an effects mask or a content mask

A mask controls coverage: it describes where something shows. In Artfkt, the target determines what that coverage affects.

  • Effects mask: limits the visible result of a whole effects stack. The image remains visible outside the masked area, without that stack’s treatment.
  • Content mask: limits the layer itself. Outside the mask, that layer becomes transparent, revealing whatever is beneath it.

For a circle of halftone on an otherwise untreated photograph, choose an Effects mask. To fill lettering with a photograph and hide the photo outside the letters, choose a Content mask. You can use both on the same image.

An effects mask applies to the entire eligible stack, not just one effect within it. If you want a different effect outside the region, plan the composition around separate layers or stacks rather than assuming each effect has its own mask.

Make a circular treatment

  1. Add an image to a new composition. Pick a picture with a clear area you want to emphasize, such as an architectural detail or part of a painting.
  2. Select the image and add an effect to its stack. For a visible starting point, try Halftone Dots. Adjust its screen size until the dots are readable at the size you intend to share.
  3. Add a shape layer and choose an ellipse. Move and resize it over the area you want to treat.
  4. With the shape selected, choose Use as mask in the active-layer inspector. Select the image as the target and choose Effects. The shape becomes an indented mask row under the image. Its coverage now limits the image’s effects stack.
  5. Select that mask row to adjust it. Start with Mask coverage: Alpha and full Mask strength. Move or resize the shape to change the treated area. Increase Feather for a softer edge; use zero for a sharper boundary.
  6. Toggle Enable mask to compare the restricted treatment with the unmasked stack. Turn the mask back on, save the project if you want to revise it, and export a still image.

The mask source stays editable: you can change the shape and placement without rebuilding the image. A source used as a mask stops contributing its own painted pixels. Detach it if you want it to become an ordinary layer again.

Add a second region or cut a gap

You can attach another shape, text, image, or video as an Effects mask to the same target. Artfkt combines masks from top to bottom within each group:

  • Add includes the new region alongside the existing coverage.
  • Subtract removes the new region from the coverage built so far.
  • Intersect keeps only the overlap.

For example, add a circle to define the treated area, then add a narrow rectangle set to Subtract to leave a stripe without the treatment. Order matters: moving the rectangle before the circle can change the result. Use the mask’s More menu to move it earlier or later, and compare the canvas after each change.

A real example: flower-filled lettering with a clear stripe

In the masking example in the Artfkt studio, an orange flower photograph fills the word BLOOM. The text is a Content mask: it reveals the image inside the letters. The same photograph has RGB Split and Posterize in its local stack. An ellipse used as an Effects mask limits those treatments to one region; a second, diagonal rectangle set to Subtract leaves a stripe without those effects.

The example uses a 24 px feather on the ellipse and 8 px on the stripe, with Alpha coverage and full strength. Those values are starting points for that composition, not universal settings: feather is measured in artboard pixels, so judge the edge at your own output size. The homepage image shows the real desktop controls and composition; the source and settings were prepared for that capture.

Troubleshoot the result

The whole image disappeared outside the shape. Check whether you chose Content instead of Effects. Content masking hides the layer outside its coverage; Effects masking limits the stack’s visible result.

The treated area is on the wrong side. Move the mask source, or use Invert mask to reverse its coverage. Check the actual edge after inversion, especially if feathering is enabled.

An effect still seems to pull from outside the region. The mask restricts where the processed result appears. Spatial effects can still sample pixels beyond that boundary. A global or inherited effect applied later can also spread beyond a content cutout.

The mask moves with the picture. Content-target masks follow the target’s move, rotation, and scale by default. Turn off Follow target transforms when the mask should stay fixed while you reposition the image.

Try it with your own work

Start with one image and one effect, then add a single mask. Once the boundary feels right, add another region or a text cutout. The halftone tutorial is a useful place to explore dot size and color; the poster layers guide shows how separate stacks affect different parts of a composition.

Explore effects in the free demo, then use the Artfkt desktop app when you want to create masks and save the composition for further editing. The demo can try the effect and export the result, but the masking steps above require the desktop app.

How this guide was made

The masking explanation follows Artfkt’s implemented desktop controls and the verified homepage composition. The cover is an original explanatory diagram, not a simulated app screenshot or a rendered effect. The product example is an actual desktop capture.