Menu Mode

This menu is a list of the different drawing modes. Commonly whenever you draw with the foreground color (drawing with left mouse button) the mode you have chosen here will be used. This mode also affects drawing primitives like lines, rectangles, circles...
Whenever possible the right mouse button uses an inverse operation like darken if the mode is brighten.
Some paint modes do color calculations. Because there are only 256 colors that can be used the quality of the result may be poor. The more colors of different kind your color table contains the better the results will be.
Some paint modes can be configured using the Settings... menu entry.

Paint

Paints with current brush as it is. That means the brush is simply stamped down.

Erase

Uses the transparent color for painting if there is no alpha layer. If alpha is enabled then the left mouse button reduces the opacity by the given value where the right mouse button draws fully transparent. In detail it works like this:
Project has no transparency
  left mouse button= foreground color
  right mouse button= background color
Project has simple transparency
  left mouse button= transparent color
  right mouse button= current background color
Project has alpha transparency   left mouse button= decrease alpha by pressure
  right mouse button= set zero alpha and draw with current background color

Selection

Instead of moifying pixels this mode will modify the mask. This way you can modify the drawing mask easily using any drawing tool. The left mouse button includes and the right excludes for masking.

Halftone

Uses the currently selected dither pattern for drawing. It will use the selected foreground and background color with the pattern.

Brightness

Brightens image colors with left mouse button and darkens with the right. You can set the strength of brightening in the Settings.

Tint

Tints image colors with brush colors. That means the brightness of each image pixel is taken and the color from the corresponding brush pixel. Both are mixed together and the result is a pixel with the brush pixel color and the image pixel brightness.

Inc/Dec Hue

Takes the Hue (color model HSV) of the image pixels and rotates it (0..360°). You can set the strength of this mode in the Settings

Inc/Dec Saturation

Increments/decrements the Saturation(color model HSV) of the image pixel colors. You can set the strength and type of this mode in the Settings

Invert

Simply inverts the image colors using the RGB-color model. A Red value of f.e. 40 will then be 215 (=255-40). The mode will try to find the best matching inverse color in the palette.

Difference

Uses difference values between image and brush colors for painting (RGB color model).

Translucent

Mixes image and brush colors. You can define a proportional weighting for this mode. That means the result color is calculated by x% of the image color and y% of the brush color and x+y=100%. See the paint mode Settings below.

Color Cycle

Uses the colors of the current gradient one after another. If the last gradient color is passed the first one is used again...

Gray

Reduces the image colors to gray levels.

Rub Through

When drawing with this mode the image that resides in the "Spare Frame" (see descriptions for menu Frame) becomes visible. You "rub through" to the spare frame.

Shade

Shifts the image colors which are part of the current gradient. So for each color the next or previous color within the gradient will be used.

Multi Shade

Shifts the image colors which are part of any gradient that is enabled for color cycling. So for each color the next or previous color within the first gradient that contains this color will be used. This only works for gradients that are set up for color cycle/multi shade. Because you might want to have gradients that are not touched by the multi shade you must enable a gradient that may be used. Just go to the gradient editor and activate color cycle/multi shade for the gradients that may be used for this paint mode.

Paint single Color

Draws using current foreground color regardless if the brush has more than one color.

Replace

Draws with the current brush but without transparency.

Smear

Smears the colors in the drawing direction. Only use with continuous painting or continuous line modes.

Blend

Smears the colors in the drawing direction and applies smoothing. Only use with continuous painting or continuous line modes.

Formula

This mode can be used to modify pixels using different types of mathematical formulas. See Settings for further information.

High Pass

Increases brightness contrasts.

Soften

Softens color contrasts and makes the image unsharp.

Soften more

Stronger soften mode.

Light Edges SE

Emphasizes edges that are nearly parallel to south, east or south east direction.

Light Edges NW

Emphasizes edges that are nearly parallel to west, north or north west direction.

Emboss I

Puts dark colored areas into the "background". So the objects look embossed.

Emboss II

Puts light colored areas into the "background".

Dither

Enable this option if you want to draw using a dither pattern. See paint mode settings for pattern selection.

Settings

Here you can change values for certain paint modes.