Revision Date: 15 January 2023

Paint Bucket Tool 
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The Paint Bucket is used to fill an area with single specific color or hue.

Position the cursor over the area to be filled and click with the Left mouse button to fill with the Primary color.  Use the Right mouse button to fill the area with the Secondary color.

Flood Modes  

The Paint Bucket has two distinct modes of operation known as the Flood Mode.  These modes dictate how the 'fill' operation works and are selectable via the Tool Bar.

Flood Mode: Contiguous - the 'fill' will continue to bleed outwards from the click point until neighboring pixels fail to satisfy the Tolerance setting.

Flood Mode: Global - the 'fill' will extend to all the pixels in the layer which satisfy the Tolerance setting.

Tolerance

The Tolerance setting in the Tool Bar is a test of conformity.  A low setting dictates that pixels must be a close match to the click point pixel in order to be filled.  A high setting allows a wider variance of pixels to be included in the fill operation.

On the left is the original image. The second image show the original fill using a Tolerance setting of 36%.  The third image shows the fill covering a larger region because the Tolerance has been increased to 42%.  The image on the right shows the fill region has increased in size again because the Tolerance has again been increased. This time to 60%.

Change color on-the-fly

It's easy to change the color of a live fill, but this can only be done while the fill is still 'active' and not finished.

To change the color of a live fill, simply change the appropriate color in the Colors window.  If the fill has been made using the Primary color, select a new Primary color in the Colors window.  If the fill has been made using the Secondary color, change the Secondary color in the Colors window.

Dragging the click point

New to Paint.NET 4 is the ability to adjust the click point of the Paint Bucket Tool while a fill is still active.  This replaces the need to undo and reapply the fill operation to a different region.

The Control Nub looks like a white square with four arrows inside it (see image below).  Click and drag this icon to relocate the click point.  The fill operation will be reinterpreted as if the user had undone the original and reapplied it using the new source point.

The image above shows an initial fill operation has colored the left gear pink.  It is easy to apply this fill to a different gear; simply drag the click point over the region to be filled.  The left hand image shows the relocated click point and the resultant changed fill. As the fill operation no longer applies to the left gear, it reverts to it's pre-filled color (yellow).

The action of dragging the click point is shown in the animation below.

Fill Styles

The Paint Bucket will fill a region with a Fill Type as specified in the Tool Bar.  This feature allows regions to be filled with one of numerous patterns rather than a solid color.

Fills utilizing a fill style will make use of both the Primary and Secondary colors.

Sampling Modes

The Paint Bucket has two sampling modes, Image and Layer.  These modes are shared by the Paint Bucket, Magic Wand Tool and Color Picker tools (shown below).  The Sampling Modes dictate which pixels will be sampled or tested to determine the extent of the fill operation.

Image - pixels are polled from the composite image to determine their suitability to be included in the fill operation.  This mode will operate in the same way as if a multi-layered image was flattened prior to using the Paint Bucket tool.  Pixels outside an active selection will be ignored and only pixels within the active layer will be subject to the fill.

Layer - pixels only within the active layer and selection (if any) are polled to determine their suitability to be included in the fill operation.  This is the same sampling mode as found in previous versions of Paint.NET.

Tolerance Alpha Mode    

This toggle button changes the algorithm which determines how the alpha channel contributes to the comparison of neighboring pixels. The states are Premultiplied (default) and Straight.

  Premultiplied results in transparent pixels being treated as equal even if the color channels are different.

  Straight results in transparent pixels being treated as equal only if the color channel values are also equal.

The Tolerance Alpha Mode toggle button is common to the Magic Wand, Paint Bucket, and Recolor tools.

Blend Modes 

The Paint Bucket can be applied using a blend mode selected from the Tool Bar.  The fill will be applied in accordance with the other parameters (Tolerance, Sampling Mode, Fill Style, etc....) then reinterpreted as if the pixels were on their own layer with the layer blend mode set.

In the example shown below, two shapes were drawn.  The Paint Bucket was applied three times: once inside each shape, and once in the overlapping region.  The first fill used the Left Mouse button, resulting in a fill in the Primary color (gray).  The second fill used the Right Mouse button so the Secondary color was used (green).  The overlapping region was filled with one of the available Fill Styles (Solid Diamond) which uses both Primary and Secondary colors.