How to make a signature photo transparent on a Mac
A photo of your signature has a white or grey box around it. Remove the background on a Mac with Preview so only the ink shows on the document.
The problem
You pasted a photo of your signature onto a document, and a grey rectangle of paper came with it. It looks pasted on, because it is.
How do I remove the white background from a signature on a Mac?
- Sign on clean white paper with a dark pen, and take a sharp, well lit photo.
- Open the photo in Preview. Crop to the signature with Tools > Rectangular Selection, then Tools > Crop.
- Choose Tools > Remove Background. If Preview asks, let it convert the image to PNG, the format that can be transparent.
- If bits of paper remain, click Show Markup Toolbar, choose Instant Alpha, and drag across the leftover background.
- Save as PNG.
Why does my signature still have a box around it?
It was saved as a JPEG, which cannot be transparent: every pixel is a colour, so the cleared background comes back as white. Export it again as PNG.
Can I skip the photo altogether?
Yes. Preview's signature tool can capture a signature from the trackpad or the camera and clears the paper for you. See sign a PDF on a Mac.
Our take
Take the photo in daylight, not under a lamp. Removing a background works on contrast: an even, bright sheet of paper comes away in one click, while a shadow across it leaves grey patches that no tool can tell apart from ink.
In Simply PDF
Simply PDF takes a photo of your signature, makes the paper clear, saves it for next time, and writes it into the page when you sign.
Questions
How do I remove the white background from a signature on a Mac?
Open the photo in Preview and choose Tools > Remove Background, or use Instant Alpha in the Markup toolbar. Save as PNG.
Why does my signature still have a box around it?
JPEG images cannot be transparent. Save the signature as a PNG.