Copying part of an image and trying to blend it smoothly into another picture is one of the trickiest options in image editing. Many times, images will look like they have been hastily cut out and dropped on top. One reason for this unwanted effect is that the sharp edges can make a selection look blocky (lighting and colours also play an important part). One quick solution to this problem is to use feathering. Like many techniques, its successful implementation will depend on the images being manipulated, but it is worthwhile learning as it has many other uses.
In the July 2003 issue of PC World, we covered the basics of anti-aliasing, a technique that introduces additional pixels to the edges of an object (see here for the full article). The extra pixels blend the edge of an object with the background colour and reduce the blocky, stepped appearance of text and shapes. Feathering utilises this blending technique in a similar way, but it is not restricted to specialised drawing features such as the Text or Draw Object tools. You can use it with a wide range of selected areas -- plus, you have greater control over its settings.
The trick with feathering is to realise it is not a stand-alone feature -- that's why you don't see a 'feather' tool listed in your program. It works in combination with various selection tools (keep in mind that there are many different tools used to select part of an image, such as wand, lasso and magic wand).
Rather than leaving a sharp edge, the feathering feature will blend the pixels between the border of the selected area and the background of the target area (i.e., the place where you will paste the feathered selection). This is an important point to remember -- after using the feather option, it is your target area that will determine the final blending of the border. If you press
The feathering process is simple to follow. Start by loading an image for testing. Click a selection tool -- this can be a lasso, marquee or other similar feature available in your program. At this stage, avoid using specialised gadgets like the magic wand. Now you may need to dig around in the selection tool's menu to find the feather option listed. In Photoshop, it will appear in the menu under Select-Feather; in other programs, you may find it in the Selection tool's palette/window. Choose a value, for example, 10: this number represents the width, in pixels, of the feathering. Now select an area of the photo, then copy and paste it into a new file with a white background. Go back to the original image and turn off the feathering. Copy and paste the selection as before, then compare the results. Follow the same technique with another photo instead of a white background. This should give you an understanding of the impact of feathering.
Since most programs use pixels as a measurement for feathering, make sure you note the pixel size of your image (or the object you are selecting). If the image you are copying is small, say 100x100 pixels, a feather setting of 10 will have a significant impact. If the image is 2000x2000 and you use the same setting of 10, the effect will be reduced substantially.
The images below show a very basic cut and paste using feathering. After selecting the bear's outline, the entire feather/copy/paste operation took about 15 seconds, with another minute or two for some quick adjustments.
Click here to see image The original image showing the selected area with feathering.
Click here to see image The unsuspecting seal in the target image.
Click here to see image The hunter and the hunted meet. Even though the edges blend well for a first attempt, they still need some touch-ups, particularly down the sides of the bear.