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Removing Parts of a Picture

The Clone Tool

This page is aimed at advanced level. This explains more practical information, with techniques that may be more complex or time consuming than other tutorials.

Sometimes when you have a picture, there may be some small, messy parts which frankly would be better off not being there. The easiest way to get rid of them is to cover them with another object - but that isn't always easy. What you need is this explanation of the clone tool.

Why do we need the Clone Tool?: Alternatives
What the Clone Tool Does
Using the Clone Tool
Hints for better results
Feathering

Why do we need the Clone Tool?

Alternatives

The first question you may have, is "why do we need the clone tool"? Surely there are other tools we can use to remove part of an image? Have a look at the nearby image - see the pink rose near the middle? Let's consider two methods of removing it:

Paste some other object over the rose.
Paint over the rose with shades of green.

Well, the first method would be great, except we don't have another image to put on top. I just want the picture to not-have that rose. This only leaves us with method two - paint over the rose.

Well, I've saved you some time on this one. I've taken the picture, done an average sampling of the green colours around the rose, and painted over the rose with them. This should look okay, right? No. Check this:

Rose painted out

Looks terrible doesn't it. And this is just a small patch. If we wanted to paint out a larger area, it would become extremely obvious. This is Not Good.

What the Clone Tool Does

The clone tool steps in to rescue us at this point. Most advanced image processing programs have a clone tool, and once you've got used to it, you can't live without it. Typically, it will have an icon like this: Clone Tool icon

The clone tool is basically another painting tool, but instead of painting using a colour, it paints with another part of the picture. Confused? Okay, it's like this. In the previous section, painting over the rose didn't work, because the solid blocks of colour are very obvious in the large area of textured green stuff. The green plants are in no way uniform. The clone tool lets us copy part of the green plant texture and blend it into the image over the rose, thus hiding it but preserving the effect of the image.

Let's see that in action to get a better idea.

Using the Clone Tool

We start with a picture with a complicated background, with a foreground object we want to remove. In this case, the rose.
We start using the clone tool. In Picture Publisher, this produces two circled cursors - the one with the cross in it is the source (where we copy from), the other is the target (where we copy to). The target can be moved around the source to any location we like. We slowly start copying the source to the target by clicking the mouse. (If you can't see the circles, just click on the image - this links to a larger version if you want.)
After cloning, we have covered the rose completely. The effect is quite good, but looks a lot better when this is placed in its original picture (you would never know the rose was there...)

Good huh? It can take a bit of time, but it is well worth it.

Hints for Better Results

I only have a few hints for using the clone tool, but they are good:

Keep moving the source area: Although the clone tool makes it possible to hide objects quite well, it is possible to introduce repeating patterns into the picture. The human eye will quickly spot these, and ruin the image for the viewer. The patterns are caused if you keep the source point still and clone it into more and more points in the picture. The same features being cloned each time are very obvious. Always vary the source area.
Don't clone over the main feature: Sounds strange, but cloning over the main feature in the picture is often bad. Cloning is most effective if the user isn't going to be studying the image in detail. Avoid having a clone feature as the image focal point.
Don't clone over too big an area: Like the previous hint, cloning over very large areas becomes obvious as the eye sees the lines and patterns in the picture don't flow so smoothly. Keep cloning to small areas only.

Feathering

The clone tool has one last feature. In most programs, the clone tool supports feathering or "blending". This tries to smooth out the edge between the clone source and the clone destination. Usually, if you are cloning textures such as grass, sand, skin tones and others, a high level of feathering is desireable, as it helps hide the effect of the clone tool.

However, there are times when feathering is bad. If you are deliberately trying to get a hard edge, such as if you are cloning the boundary between two distinct objects, then you will probably want to reduce the feathering to 20% or less. Otherwise you will get a short point on the edge which is all fuzzy - naturally, this can look out of place.

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This page was created by James Corrin. All pictures and text belongs to him or the appropriate author. Permission to use any pictures or text from these pages must be sought from the work's author. This page was last updated Saturday 22 January 2000. Email: webmaster@imageeffects.8m.com