Flood Fill Tool

The flood fill tool fills an arbitrary area of an image with color, according to the current fill color. To perform the fill, just click a point on the image. The place you click and the surrounding area will be filled with color until a border is reached

There are two flood fill modes: Fill until border color and fill until different color. The latter is generally the more useful mode because it takes the color of the place where you click, then floods until it finds a different color. The fill until border color mode, on the other hand, won't stop filling until it reaches a border of a particular color that you specify beforehand using the color picker beside it.

Both filling modes use the tolerance value, which specifies how "close" colors have to be to be considered a border color. Generally, if you're trying to fill an area that contains a wide range of colors, you'll want to use a higher tolerance value. If the tolerance value is too high, however, the flood filler could end up filling the entire image with color. Sometimes you have to experiment with the tolerance value to get exactly what you want. A tolerance value of 0% means that the color has to be exactly right. If you're using "fill until different color", then, adjacent pixels have to be exactly the same or they won't be filled, and if you're using "Fill to border color", then the pixel has to be exactly the right color or it won't be considered a border.

An example of using flood fill is shown to the right.

Put a check mark beside "Border" to draw a border around the flood-filled area using the current line color. By default, the current pen will be used as a border, but you may also choose thin pen for a single-pixel border.