Fill Panel and Gradient Panels

The fill panel is host to Howler's fill settings, used by tools like the floodfill tool, rectangle and ellipse tools, and the curve tool, to name a few.

On the top, left, is a preview of what your fill may look like.

To its right are the opacity and dither drop-sliders, as well as an option to make dithering monotone.

The Plain color option button fills using just one single color which is determined by your current primary (or secondary when drawing with the right mouse button) colors.

Fill modes are similar to drawing modes, except that they are used by fill tools. Fill modes let you combine a fill with the existing image in various unique ways.

The Pattern fill option button fills using the current custom brush as a source for the pattern. The pattern will repeat as many times as needed to fill the desired shape. The pattern will always be the same size (same number of pixels) as the original custom brush. Several other modes will re-size the pattern as needed.

The warp fill modes will warp the pattern in unique ways to fill a given shape.

Anti-aliasing ensured that the warp fill is smooth and realistic looking and not blocky, but sometimes you may need to turn it off, so there is a check-box for it.

The gradient fill modes are similar, but use a gradient instead of a pattern.

See below for more information on these modes.

Warp modes

There are many ways to fill a shape with a gradient, and many types of gradients.

You can use any of the fill tools on the tool panel to fill a shape.

You can also use an alpha channel tool, and fill it either with the paint can, or by pressing the 'q' key.

That is the method that was used for all of these examples.  Pressing the 'q' key will fill the alpha selection with whatever fill mode you have selected on the Gradient/fill panel.

You can see in the examples the various modes offered.

In these examples, the second row of icons were used to select a brush warping mode.

Brush warping uses the current custom brush as an image or pattern.

Each mode warps the brush in different ways, as you can see.

You can achieve a nice globe by warping a brush of a map into a sphere using the 'warp both' mode.


In the center of the panel, you have a control that adds some dithering to your fill.  This can be useful for breaking up gradients that might tend to look plain, otherwise.

Color dithering is used in the first image, and no dithering in the second.


The Modes menu lets you select the fill mode that is used for filling shapes.  You will find these similar to drawing modes used by brushes, except that they are used by the fill tools.

Selecting and Editing Gradients

There are several ways to edit a gradient in Howler. One way may be better for certain needs.

To begin with, when you need to select a gradient for use by various tools, you can do so with the gradient drop-down control found on the context strip for tools that allow filling with a gradient such as the floodfill, rectangle and ellipse tools, or tools that use gradients for other functions, such as the fx tool.

You can choose to edit a gradient from here, or from the Window menu, by selecting “Gradient editor” or “Sweep editor.”

Blocks of 8 gradients are always loaded at the same time. The one you click on will be an index into that list of 8.

The Gradient editor

You can edit a gradient in Howler using the gradient editor.

To add a “color stop” or “entry” to the gradient, just click on the big color swatch in the middle of the panel. Then click on the color box in the left, top corner to edit that entries color.

Alternately, you can edit an existing entry by clicking on it's mark that looks like an arrowhead, then clicking on the color box in the left, top corner.

You can also set the opacity for that entry with the box marked “A” which stands for “Alpha.”

Gradients in Howler are stored in groups of 8, so you can select any index in the group to work on using the “Gradient index” slider at the bottom.

The “Modes” drop-slider lets you pick several additional ways of working with your gradient.

You can chose between linear, cosine, and cubic interpolation. Linear is the most predictable, as the colors are simply blended directly from one to the next. Cosine mode attempts to smooth out the blends by using a cosine function. The Cubic interpolation mode creates a smooth blend between each color, but it can be a little unpredictable at times.

The HSV color model does the color blend in Hue/saturation/value space, meaning blends will take place around a color wheel. Additional colors may be introduced in such a case.

The Sweep editor is called that because you can “Sweep” your mouse over the channels of color to edit them interactively. You can also edit a gradient in a more traditional way by adding “color stops/”

You can use drag and drop to drop colors onto the area that looks like a ruler at the bottom to add color stops, and a gradient will be created by blending between them.

An opacity channel is included, so you can make parts of your fills transparent.  While the color channels can be created with drag and drop, you must edit the opacity channel manually by sweeping over it.

You can see how part of this fill has become transparent.

There are times when you want to smooth out the curves you create when editing a gradient.

Holding the Smooth button down will smooth out your curves until you let it up.

The Auto smooth button next to it will continue to smooth curves as you edit them until you deactivate it.

  The index slider lets you select or edit any one of 8 gradients.  Gradients come in sets of 8, so there can be lots of variety.

You can also load and save gradient sets.  There are quite a few that come installed.