Looking to insert a badge in a document, or a product’s image into a picture? Find out here how to make an image transparent on a Mac using Preview.
First, Alvy Ray Smith Knows Where the Good Images Are
In the pink building of New York Institute of Technology, Alvy Ray Smith helped Ed Catmull find just those background images to blend with particular foreground images. This was important work for Catmull’s upcoming paper—and it was excessively tedious.
Wouldn’t the blending and rendering be so much faster, wondered Catmull, if each pixel of the foreground image contained information not only about its color but als about its opacity?
“This is extremely easy,” said Smith and set to work.
One night later, the extra bit of information for each pixel’s transparency was ready—and named.
From the interpolation expression (as you intensify one object, another blended with it decreases proportionally), they took the first letter—alpha—to call their so helpful invention the alpha channel.
Now, to find out just how helpful that bit of information is, let’s add it to an image on a Mac:
How to Make an Image Transparent on a Mac Using Preview
Time needed: 4 minutes
To add translucency to an image using the Preview app built into any Mac:
- Show the Markup toolbar in Preview.
Here’s how: Click the Show Markup Toolbar button in the Preview toolbar so it is enabled.
Preview keyboard shortcut: Press Command Shift A to toggle the markup toolbar. - Click Instant Alpha in the markup toolbar.
- Click (and hold) in a part of the image you want to make transparent.
- Drag in any direction from the origin to progressively add (less and less similar) adjacent colors to the selection.
Undo: Drag back in the direction of the selection’s origin to remove colors.
- Let go of the mouse cursor.
- With the marching ants selection visible, press Del or Backspace.
Convert to PNG: If you edit an image in a format that does not support transparency (such as a JPEG image, for instance), Preview offers to convert the image to PNG (which does support alpha channel opacity); click Convert.
- Repeat steps 2–6 to make more parts of the image transparent as desired.
- Optional: Use the rectangular or lasso selection tool to highlight and delete pieces you missed with Instant Alpha.
- Save the image.
Alpha: To save with translucency information, do check Alpha when you export the image.
How to Make an Image Transparent on a Mac Using Preview: FAQ
Does the transparent part have to be the background?
No.
In Preview, you can make any part and color translucent. In any event, start with the center (or the most typical color value) to select.
What file formats will retain the alpha channel information?
In Preview you can use the following file formats for saving with transparency:
- HEIC
- JPEG-2000
- OpenEXR
- PNG
- TIFF
(How to make an image transparent on a Mac using Preview tested with macOS Sonoma 14.2–14.3, Ventura 13.3 and Monterey 12; first published June 2023, last updated May 2024)