The profile photo on a Mac computer is also known as the user's photo. This photo is shown when you sign in to your Mac account, and when you use apps like iChat and Address Book. While a profile photo is generally selected when you first set up your Mac, you can change the photo at any time via the System Preferences menu.
Step
Part 1 of 3: Accessing User Profile Photos
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Step 1. Open the Apple menu
Click “System Preferences”, then click “Users & Groups”.
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Step 2. Log in as administrator
Click the padlock icon to unlock the settings, then enter the administrator username and password.
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Step 3. Select the user account you want to change by clicking on the image
You will see a menu to select the image source.
Part 2 of 3: Selecting Image Source
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Step 1. Select the category for the image you want to use
You'll see several options, such as "Defaults" (the default OS X image). "Recents" (photos of recently used users), and "Linked" (photos from contacts). You can also select the "Faces" option, which allows OS X to detect and extract faces from your saved images. Select "iCloud Photos" to use photos that have been uploaded to iCloud. If you want to use the photo you just took, read the next steps.
You need to enable iCloud photo library before you can use it as a profile photo source. On the Apple menu, click “System Preferences”, then “iCloud”, then “Preferences” (next to “Photos”). Select “iCloud Photo Library”
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Step 2. Click "Edit" on the button below the image selection
You can enlarge part or all of the photo, then crop the profile photo you want to use.
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Step 3. Click the photo you want to use, then click "Done"
The profile photo of the user you selected will change.
Part 3 of 3: Using Photos from Webcams
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Step 1. Click the "Camera" option from the menu that appears after you click on the user's image, among other image source options
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Step 2. Click the camera button that appears
The camera on your computer will take a picture after 3 seconds.
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Step 3. Click "Edit" on the button below your photo
Crop the image as desired.
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Step 4. Click “Done”
The profile photo of the user you selected will change.