Defines the way non-maxima are detected.

Values of this enumeration:

• Nearest - Checks the nearest of the four basic direction: horizontal, vertical and two diagonals.
• Interpolated - Checks one precise direction, interpolating pixel values.
• InterpolatedPlus - Checks one precise direction, interpolating pixel values, with an additional check.
• Double - Checks the two nearest of the four basic directions.
• Quadruple - Checks the two nearest of the four basic directions, but also not straight.