Check a cut-out portrait before putting it on a slide
The cut-out looked perfect on the white slide. Then someone switched to the dark template, and a pale outline of the old office wall appeared around your colleague's hair.
What you'll make
a transparent PNG of a person, cut out from their original photo, that you have checked on a light and a dark slide.
What you'll need
a photo of yourself, or of an adult who has agreed, with the person clearly separate from the background. PowerPoint for Microsoft 365 (or 2021/2024) on Windows or Mac, or another editor with background removal. Keep the untouched original. To practise, use the fictional home-desk photo. About ten minutes.
Example result.
| Check | Pass looks like |
|---|---|
| Real transparency | The slide colour shows through around the person |
| Edges on a dark slide | No pale band or leftover wall around hair, ears or shoulders |
| Person unchanged | Face, light and clothes match the original exactly |
1. Remove the background in PowerPoint
Insert the original photo on a blank slide and select it. Choose Picture Format › Remove Background (on a Mac, Format › Remove Background). PowerPoint colours the part it will remove magenta. Use Mark Areas to Keep to draw over any part of the person that has turned magenta, and Mark Areas to Remove over any background it has kept. Then select Keep Changes.
Why this works: background removal keeps the camera’s pixels for the person and only deletes the rest. An AI image generator asked to “remove the background” redraws the whole picture, face included.
What you should see: the person on the white slide with no background, and nothing magenta left on them.
2. Save it as a PNG
Right-click the picture and choose Save as Picture, then pick PNG as the file type. PNG can store an alpha channel: information about how transparent each pixel is. A JPEG can’t, so it will fill the background with white.
Why this works: the slide preview isn’t the file. Saving and reopening the PNG is how you know the transparency travels with it.
What you should see: a .png file. Insert it on a new slide and the slide colour shows around the person.
3. Check it on a dark slide
Put the saved PNG on a dark slide, such as navy or dark teal, and zoom in on the hair, ears, glasses, neck and shoulders. A pale halo that’s invisible on white is obvious on dark. Then put the original photo next to it and compare the face, light and clothes.
A painted checkerboard inside the picture will not become transparent because it resembles an editor’s transparency grid. If the “transparent” area looks grey and white on a dark slide, the file isn’t transparent.
Why this works: each of the three checks catches a different fault. Clean edges don’t prove transparency, and transparency doesn’t prove the person is unchanged.
What you should see: the dark slide colour right up to the hair and shoulders, and the same face as the original.
Check the result
- The dark slide shows through around the person.
- No band of old background or pale outline is left around hair, ears or shoulders.
- The face, skin tone, light and clothes match the original.
- Fine hair has a soft edge rather than a hard cut-out line.
The usual failure: a pale halo or a patch of old background that only shows on a dark slide. The automatic removal keeps a little of a wall that’s close in colour to hair or skin. Spot it by zooming in on the dark-slide version. Fix it in the editor first (Mark Areas to Remove over the patch). If you need a second opinion on what you’re seeing, attach the original and a screenshot of the dark-slide version to a chat and ask:
The first image is my original photo. The second is a screenshot of my
cut-out on a dark slide. Name any visible leftover background or pale
outline around the hair, ears or shoulders, and any change to the
person, as separate lists. Say where each one is. A screenshot can't
show transparency data, so don't comment on that. Do not generate
a new image.Worked example: the chair that stayed behind
Fictional example. The practice photo shows a man in a navy T-shirt at a home desk, with a grey office chair, a bright window and a bookshelf behind him.
- The white-slide check passed. Suppose PowerPoint’s automatic pass keeps a sliver of the grey chair back beside his shoulder, on the viewer’s left. On a white slide, it reads as a shadow.
- The dark slide caught it. On dark teal, the sliver shows as a grey wedge, and the bright window leaves a faint pale outline along the top of his hair. Select the picture, choose Remove Background again, and use Mark Areas to Remove across the wedge and the outline. Keep Changes, Save as Picture as PNG again, and recheck on dark teal.
- The face check needed no work, because nothing was redrawn. That’s the point of using removal. An image generator also produced a transparent file from this photo — its first attempt — but it brightened the face and changed the shirt folds, so it failed a removal-only brief however clean its edges were.
Try it
Check a cut-out on light and dark slides
Switch the slide behind an image generator's transparent cut-out, then compare the person with the original.
The AI skill: Check transparency, edges and the person as three separate things.
Loading the controls…
The edges hold up on the dark slide. Compare the face and shirt with the original photo: the face is brighter and the folds differ, so it fails a removal-only brief.
Changing the preview background does not repair the PNG. The alpha view is a direct extraction from the retained file: black is transparent, white is opaque and grey is partial. It is not an AI-generated mask or quality score.
Choose the next AI job
Ask AI to name visible differences and state inspection limits. Read the actual file in your editor: the original raw-preview haze diagnosis was corrected when true transparency was composited. A screenshot alone may mislead.
Your instruction preview
Inspect my permitted original and exported portrait candidate. Name visible background residue, hair/shoulder boundary problems and changes to the person separately. Do not assume transparency from a screenshot or checkerboard. If you cannot inspect the actual alpha channel, say so. Suggest one specific next action using the untouched source; do not generate a new portrait or invent hidden hair or body detail.Try it on your work: Put your own saved PNG on a light and a dark slide, then compare the person with the original before you use it.
Go deeper
Match the fix to the fault
Each fault has a different fix, and the wrong one makes things worse. Asking a generator to “remove the halo” from a file that is really opaque, for example, just redraws the person.
| What you see on the dark slide | Next action |
|---|---|
| White or a painted checkerboard where the slide should show | Save again as PNG and check the background is set to none |
| A band of old background or a pale outline | Mark Areas to Remove over it, then save again |
| Hair, an ear or clothing cut away | Mark Areas to Keep over it, then save again |
| A different face, light or clothes | Start again from the original with a removal tool, not a generator |
No PowerPoint? Use your usual editor
Keynote and Adobe Express have background removal, and so does Canva on paid plans. In Adobe Express, select the image and choose Remove Background, then set the canvas background to No fill and download as Transparent PNG; check your plan offers that file option. Whatever the tool, run the same three checks on the saved file. If no editor gives an acceptable cut-out, put the ordinary photo in a rectangular frame on the slide instead. A neat rectangle beats a fuzzy outline. Once a cut-out passes, set any brand colour behind it with a slide fill, which is exact in a way an image generator’s hex code isn’t; the brand-colour portrait guide covers this.
Ask AI to plan the steps for your editor
If you’re not sure what your editor can do, ask a chat to plan it rather than to make the image:
I need a cut-out of a person from their original photo, for a slide.
The person, lighting and clothing must stay unchanged.
I am using [editor].
Explain the background-removal steps, how to restore fine edges and
how to save a PNG with real transparency. Ask me which menus I can
see before naming specific controls. Do not generate a new image.[editor] is the app and version, such as “Keynote on a Mac”. Check the steps against that editor’s own help page.