When you are creating a digital presentation or designing a flyer, you often need to insert a logo or a photograph of a product. However, those images usually come surrounded by a solid white background block, which looks terrible when placed over a colored slide. You do not need to hire a professional graphic designer or purchase an expensive Adobe Photoshop license to fix this. You can use the macOS Preview application’s hidden “Instant Alpha” tool to magically erase the solid background, rendering it completely transparent.
How to Use the Instant Alpha Tool
The Instant Alpha tool acts like a digital magic wand. You click on a specific color (like a solid white background), and the software mathematically selects every connected pixel of that exact same color.
- Double-click the image file to open it in Preview.
- Look at the top-right corner of the Preview window. Click the Show Markup Toolbar button (the small pencil tip icon).
- On the new horizontal toolbar that appears, click the Instant Alpha icon. It is located on the far left side, and looks like a magic wand with tiny stars sparkling around the tip.
Your mouse cursor will transform into a crosshair.
How to Select and Delete the Background
Carefully move your crosshair cursor over the solid background color you wish to delete (e.g., the white area surrounding the company logo).
- Click and hold your left mouse button down.
- Slowly drag your mouse slightly downward or to the right.
As you drag, a bright red highlight will spread across the background like spilled paint. This red highlight indicates exactly what pixels the software is about to delete. By dragging the mouse further, you increase the tool’s “tolerance,” allowing it to grab slightly different shades of white near the edges of the logo. Be careful: if you drag too far, the red highlight will bleed into the logo itself.
Once the background is perfectly highlighted in red, simply release the mouse button. The red highlight will disappear, replaced by a “marching ants” dotted selection line.
Press the Delete key on your keyboard. (If the original image was a JPEG, Preview will throw a warning that it must convert the file to a PNG to support transparency. Click “Convert”). The solid white background will instantly vanish, replaced by the grey-and-white checkerboard pattern that universally signifies a transparent background.
Press Command + S to permanently save the newly transparent PNG file, ready to be seamlessly dropped into your presentation.