Original examples · Cutout · public alpha
How to check a transparent PNG after background removal
Test notes updated October 10, 2026 · by thecreatingco
A transparent PNG needs a real alpha channel. A checkerboard drawn into the picture is still opaque. After removing a background in Cutout, inspect the exported file over both light and dark colors and look inside any holes in the subject.
Try a controlled edge example
Our original 256 × 256 purple ring gives you three things to check: the outside silhouette, the empty center and background color left on the edge. This deliberately simple example has no hair, glass or shadows. It is useful for checking an export, not for judging photographic segmentation quality.
Download the source PNG · Download the transparent reference
What Cutout actually exported
Download the observed Cutout result. Pixel inspection found an alpha value of 0 at the top-left corner and 255 at the center (128, 123). The outer background became transparent, while the empty center stayed cream. This is a successful download with an imperfect automatic mask, not a finished cutout.
Remove the background, then check the file
- Open Cutout and choose the source PNG. Keep that original separately.
- Run the removal and inspect the subject. The hole in the center should be empty, not filled with cream. Refine any missed regions using the controls available in the current workspace.
- Export PNG. Open the downloaded file in a viewer or layered editor that displays transparency.
- Place it over white, near-black and a saturated color. Look for a pale fringe, missing purple pixels and an opaque rectangular background.
- Compare it with the supplied reference at the same scale. A successful flat-shape test says nothing about fine hair or translucent fabric; test your actual subject next.
Why a cutout can look right and still fail
| What you see | What to check |
|---|---|
| White rectangle after download | Confirm you exported PNG with transparency. A white viewer background alone does not prove opacity; place the file over another color. |
| Checkerboard stays visible everywhere | The checkerboard may be pixels in the image. Use the reference file to compare actual transparent areas. |
| Light halo on a dark background | Inspect boundary pixels and refine the mask. A background-colored fringe is much easier to spot on an opposing color. |
| Hair disappears | Return to the original and refine conservatively. Increasing contrast or deleting more edge pixels can worsen missing detail. |
| Shadow looks abruptly clipped | Decide whether to retain a soft shadow or create one in the destination composition; a solid subject mask and a shadow are different decisions. |
A real-photo test: fine hair against a marina
We also ran Cutout on the existing Jensen Westerlund portrait from our About page. Unlike the flat ring, this photograph has flyaway hair, a beard, blue sky, boats and thin masts close to the subject. We clicked Remove background once and downloaded PNG, with no mask brush edits and Feather at 0.
The marina was largely removed, but this first pass retained a soft blue fringe near the hair and background remnants along the beard. The checkerboard preview made those areas less obvious than an opposing solid background. This example needs manual refinement before a clean portrait composition.
The exported image retains the original 1,163 × 1,635 dimensions. Pixel inspection found 715,045 fully transparent pixels and 275,321 partially transparent pixels. Those counts confirm an alpha channel; they do not measure whether the mask correctly follows the person. We have no hand-labelled reference mask or photographic accuracy score.
Inspect the full-size actual export · Portrait source: thecreatingco About page. The portrait and this derived example retain their original rights and are excluded from the reusable synthetic-fixture permission below.
For your own photograph, inspect flyaway hair, gaps between strands and any thin background lines touching the subject. Restore lost subject detail or erase remaining background in small passes, then inspect a new export on both light and dark surfaces. Adding Feather can soften an edge, but cannot decide which remaining pixels belong to the subject.
Cutout or a layer mask in Luma?
Use Cutout for a focused subject-removal task. Use a layer-mask workflow in Luma when you need the subject, background, text and corrections to stay together as an editable composition. Neither route guarantees a clean edge. Keep an editable copy until you have inspected the delivery image in its final layout.
PNG can represent per-pixel transparency; that does not mean every PNG file contains transparent pixels. The file format and the quality of the subject mask are separate checks. Source: W3C PNG specification.
What this example proves
The reference has transparent background pixels and an opaque purple subject, including a transparent central hole. We generated both fixtures directly from original geometry. The actual automatic result is shown separately and has a missed center hole. We have not measured accuracy on photographs. Cutout remains a public alpha; fine hair and translucent objects require individual review.
Reuse the examples
The synthetic ring fixtures may be reused and modified, including commercially. The portrait test above retains its original rights and is excluded. Read the fixture notes and limits. Keep originals and inspect actual exports before delivery.