In some cases, you may want to blur certain parts of a photo when posting it online. For example, you need to blur faces of those people who do not want to appear in the photo. The Preview app which is bundled with the Mac OS provides us the easiest way to black out parts of images on Mac.
Method 1. Remove a part of picture in Preview
Find the picture in Finder, double click to open it with Preview. Drag and drop to select the area you want to blur or pixelate, hit the ‘delete‘ key on your keyboard. Then save the image.
If you want to keep the original copy, make sure to duplicate the picture in Finder first.
Method 2. Annotate photo in Preview
Open the photo in Preview. From the top menu bar, select Tools >> Annotate >> Rectangle. This will add a rectangle shape on your photo. Drag it to any area on your photo at the background. Drag the borders to adjust its size, choose color of the border and the rectangle shape to override the area you want to blur or black out.
Blur pictures using Photos app
The Photos app on Mac, iPhone and iPad can also help us pixelate or blur image files. Check out this guide to blur pictures using photos app on iPhone for more details.