FLOODFILL is a drawing tool capable of filling areas consisting of similar pixels.
Tolerance parameter controls how different may the pixels be to be considered close enough to be painted.
In most cases, the "Simple flood fill" mode should be used. Click on the image and eventually move the mouse with left button down to experiment with the source point. After the mouse button is released, the operation is applied.
If you wish to have more control over the process, use the "Multi-point flood fill" mode. In this mode, you can change color before applying the action and move the source point using a control handle. You can also select multiple source points. Apply the action with ENTER key, from a context menu or using a Down->Right mouse gesture.
How to use the flood fill (also known as the paint bucket) tool.
Open an image a switch to the flood fill tool. Its configuration panel appears. It allows you to select the number of source points, the matching mode and its tolerance.
So, click on the image. This is not a trivial case and the result is not optimal. We may need to switch to the "Multi-point" mode. Do it.
Note that after clicking now, a control point appears and you can freely drag it around or change the values in the configuration panel. Click again at a different place to designate a second flood source. Another thing you can change is the color (or use a more complex fill style). You can use any number of source points. To remove a source, drag it out of the canvas.
Let me open another image that is more suitable to demonstrate how the matching modes work.
I'll start in the multi-point mode. The RGBA mode takes all color channels into account. The Hue mode disregards brightness and saturation. The Brightness mode on the other hand disregards Hue. The Alpha mode only considers level of transparency. The tolerance setting controls the accuracy of the selected matching mode.
Be aware that using flood fill will usually make smooth edges not so smooth, because a pixel is either filled or left alone.
When filling you can also adjust transparency of the color and if you are using semitransparent color the "Replace" blend mode may be of use.
Now, click the Tool presets button and select Manage custom presets. In the window, click on the "Create new preset" icon. Name your new present and then carefully fill the Edit tool box with RETOUCH underscore FLOODFILL - user upper case letters and no spaces.
Click on the new item in the Tool presets popup menu. Note the retouch tool configuration above Flood-fill configuration panel.
Instead of simple filling, you can now Brighten, Darken, Desaturate, Colorize the affected pixels and more. Experiment with the available combinations.
Unlike the plain flood fill, the retouch modifier preserves the features of the affected pixels, namely the gradient and the reflection. Also, the edges remained smooth, because the pixels were not overwritten, merely affected by the selected operation.
The flood fill tool can also be used with a selection. If I create an ellipse selection and then use the flood fill tool, only the selected region is affected.
So, this is what the current flood fill tool can do. I hope you'll find it useful.
FLOODFILL tool can be used from scripts. The command in script may have 2 to 4 parameters:
DrawTool.FLOODFILL(Document, 100, 100, 10, "HLSA");