Using Preview to adjust the colors in an image

When I need to work on a piece of new equipment that has a power adapter, I usually note the model number and part number for the power adapter in case the adapter should be separated from the equipment later, so that I can easily determine which adapter goes with which piece of equipment and so, if a wire within the cord for the adapter gets broken over years of use, I can easily locate a source for a replacement if needed. I sometimes also take a photo of the power adapter, so I know what it looks like if I'm searching through boxes of adapters for the correct one.

So I took some pictures of the adapter for a new HP 15-af131dx notebook. I used a station my wife has in her studio for taking photos that has a white cloth for a backdrop and lights that are focused on the area to be photographed. But I used my cell phone to take the photos rather than the camera she uses. Even though I made some adjustments to the phone's settings for taking photos so that the images had a white background when I viewed them on the phone, when I uploaded them from the phone to a computer I found that the white backdrop looked somewhat gray when I viewed them on a couple of computers.

On my MacBook Pro laptop, I normally use the Preview program, which is found in the Applications directory on OS X systems, to view images. That application provides color adjustment capabilites that allowed me to easily adjust the colors in the image so that I got the whiter background I wanted for the images. After opening a photo in Preview, I could click on Tools then Adjust Color to bring up an Adjust Color window where I could change the following values for an image:

Preview - Adjust Color

I started with the photo below:

HP power adapter Part No. 740015-002

To whiten and brighten the image, I first clicked on the Auto Levels button, which modified the image as shown below:

HP power adapter PN: 
740015-002 Auto Levels

To further lighten the background and produce a black and white image, I then moved the slider for Saturation all the way to the left, producing the image below:

HP power adapter PN: 
740015-002 Auto Levels and Saturation

If, after making changes to an image, you wish to revert to the original image, you can click on the Reset All button near the bottom of the Adjust Color window.

For further tips on adjusting an image's tonality and color with the OS X Preview application, see Discover Preview's hidden image editing powers.


  1. Discover Preview's hidden image editing powers
    By: Derrick Story
    Date: September 2, 2010


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