How to make a PNG with a transparent background
Last updated: 2026-07-27
You drop a logo into a document and it arrives wearing a white box that covers the table border behind it. The fix is a transparent background — but understanding what transparency actually is explains why some images clean up in one click and others fight you for twenty minutes.
Transparency means an alpha channel
A pixel in a normal image is three numbers: red, green and blue, each from 0 to 255. Images that support transparency carry a fourth number per pixel, the alpha value, which describes opacity. Alpha 255 means fully opaque — nothing behind it shows through. Alpha 0 means fully transparent, and that pixel is effectively not drawn at all. Values in between are partially see-through.
So a transparent background is not a background painted white. It is a region where the alpha values are zero and no colour is drawn. Hold onto that distinction; everything below follows from it.
JPG cannot be transparent, ever
The JPEG format has no place to store an alpha channel. It was designed for photographs, where every pixel has a colour and nothing needs to be see-through. Save a transparent image as JPG and the transparent areas get filled in — usually white, sometimes black. This is why a logo you downloaded as a transparent PNG can suddenly grow a white box: somewhere in the chain, someone opened it and re-saved as JPG, and the transparency was flattened permanently. It cannot be recovered by renaming the file. If you need transparency, the file must be .png. (WEBP, GIF and SVG also support it, but PNG has the best support across document tools.)
PNG-8 versus PNG-24
Not all PNGs handle alpha the same way.
- PNG-8 limits the image to a palette of at most 256 colours, and its transparency is binary: a pixel is either fully opaque or fully invisible, with nothing in between. That makes curved and diagonal edges look jagged, because there are no partial pixels to smooth the transition. It is fine for flat-colour icons and produces very small files.
- PNG-24 (technically PNG-32 once alpha is included) has no colour limit and stores 256 levels of alpha. Edge pixels can be partially transparent, so the outline blends smoothly into whatever sits behind it. Signatures, photographs and any logo with a gradient need this.
If your export dialog offers 8-bit or 24-bit, choose 24-bit unless file size is genuinely critical.
White and transparent look identical — until they do not
Place a white-background PNG and a transparent PNG side by side on a white page and you cannot tell them apart. The difference only appears when something is behind the image: a coloured table cell, a grey header band, a photo, a line of text. At that moment the white background reveals itself as an opaque rectangle.
So build a checking habit: never verify transparency against white space. Drag the image temporarily over a coloured or text-filled area. If a rectangle appears, it is not transparent. People routinely approve an image sitting in the margin and only discover the problem after moving it onto a table.
Where to get transparency from
The best transparent PNG is one you never had to make. For a company logo, the marketing team or the brand assets page almost always has a proper transparent PNG or an SVG. Anything scraped from a website screenshot or lifted out of a slide deck has already been composited against a background and will never be as clean as the original.
When you do have to create it, an image editor is the general answer: delete the background layer and export as PNG. Free options include GIMP, Photopea (runs in the browser) and Paint.NET. Recent versions of Windows Paint have a background removal button, but you must choose PNG when saving or the transparency is discarded.
If all you need is to strip a white background from an image you are putting into a document, an editor is overkill. In StickPDF, place the image and press Remove background: white and near-white pixels become transparent, and that cleaned version is what gets embedded in the exported PDF. Restore background puts it back if you change your mind.
The threshold problem with off-white and grey
Automatic background removal works by picking a threshold: pixels brighter than some cutoff become transparent, pixels darker stay. On a genuinely clean white background this is flawless. On a cream-coloured scan, or a photo where one corner sits in shadow, it stops being flawless — and the reason is structural, not a flaw in any particular tool.
Lower the threshold so it removes more, and the grey background finally disappears — along with the faded tail of a pen stroke and the soft grey tones inside a logo, leaving broken, gappy shapes. Raise it so the strokes survive, and patches of background survive too. When background and content are close in brightness, no threshold gives a clean result.
So the fix is upstream, in the input rather than the algorithm. Re-scan or re-photograph in even, bright light. Or open the image in any photo editor and push the brightness and contrast until the background clips to true white while the content stays dark. Once the background sits near 250 and the content below about 50, almost any threshold separates them cleanly.