Cutting object out of background using 'Smart Lasso' and 'Instant Alpha' in Preview

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Cutting object out of background using 'Smart Lasso' and 'Instant Alpha' in Preview

With Preview on OSX.14.6 (Mojave), I'm using 'Smart Lasso' and 'Instant Alpha' to select and pull objects out from the background. Two files are in question here, both originally JPGs, now converted to PNG for transparency. One of them worked just fine: object selected with 'Smart Lasso', copied to paste buffer, then 'New File from Clipboard' created new image — no problem. The second file just won't work, for some reason, though all settings and parameters seem to be the same.

Having selected the object with 'Instant Alpha' because it's quicker and easier and this second object is just one black object with clearly defined edges on a white background, object is then selected and copied BUT when a new image is created from the clipboard, the whole image is black. There is a vague outline of the object, but I can't find any way to pull it away from the now-black background. What's going on?

Mac mini, macOS 10.15

Posted on Aug 30, 2023 3:42 PM

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Answer 1

kamote0628

Community Specialist

Aug 31, 2023 12:34 PM in response to McD.ee

Hi McD.ee,

We appreciate you reaching out to us.

We’d like to gather additional details that may help us be in a better position to assist you.

After copying a portion of an image, do you paste it on a different image that is also opened through Preview?

In the meantime, please check if the issue persists while on safe mode.

Safe mode can help determine if the issue is caused by a third-party software.

Performing this step may help resolve the issue, or further isolate the issue.

Below is an article to help guide you through the process.

Use safe mode on your Mac - Apple Support

If the issue persists, please test if the issue happens on a newly created user account.

"On your Mac, choose Apple menu > System Settings, then click Users & Groups in the sidebar. (You may need to scroll down.)
Click the Add Account button below the list of users on the right (you may be asked to enter your password.)
Click the New Account pop-up menu, then choose a type of user.
Enter a full name for the new user. An account name is generated automatically. To use a different account name, enter it now—you can’t change it later.
Enter a password for the user, then enter it again to verify. Enter a password hint to help the user remember their password.
Click Create User."

You can use the article below as a reference.

Add a user or group on Mac - Apple Support

Take care!

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