Set the alpha filter color value and x, y
Example:
filter.set_alpha x, y, Imlib2::Color::RgbaColor.new 0, 0, 0, 128
Set the blue filter color value and x, y
Example:
filter.set_blue x, y, Imlib2::Color::RgbaColor.new 0, 0, 64, 128
Set the green filter color value and x, y
Example:
filter.set_green x, y, Imlib2::Color::RgbaColor.new 0, 128, 0, 128
Set the alpha filter color value and x, y
Example:
filter.set_alpha x, y, Imlib2::Color::RgbaColor.new 0, 0, 0, 128
Set the blue filter color value and x, y
Example:
filter.set_blue x, y, Imlib2::Color::RgbaColor.new 0, 0, 64, 128