module ChunkyPNG
class Canvas
# Module that adds some primitive drawing methods to {ChunkyPNG::Canvas}.
#
# All of these methods change the current canvas instance and do not create a new one,
# even though the method names do not end with a bang.
#
# @note Drawing operations will not fail when something is drawn outside of the bounds
# of the canvas; these pixels will simply be ignored.
# @see ChunkyPNG::Canvas
module Drawing
# Composes a pixel on the canvas by alpha blending a color with its background color.
# @param [Integer] x The x-coordinate of the pixel to blend.
# @param [Integer] y The y-coordinate of the pixel to blend.
# @param [Integer] color The foreground color to blend with
# @return [Integer] The composed color.
def compose_pixel(x, y, color)
return unless include_xy?(x, y)
compose_pixel_unsafe(x, y, ChunkyPNG::Color.parse(color))
end
# Composes a pixel on the canvas by alpha blending a color with its background color,
# without bounds checking.
# @param (see #compose_pixel)
# @return [Integer] The composed color.
def compose_pixel_unsafe(x, y, color)
set_pixel(x, y, ChunkyPNG::Color.compose(color, get_pixel(x, y)))
end
# Draws an anti-aliased line using Xiaolin Wu's algorithm.
#
# @param [Integer] x0 The x-coordinate of the first control point.
# @param [Integer] y0 The y-coordinate of the first control point.
# @param [Integer] x1 The x-coordinate of the second control point.
# @param [Integer] y1 The y-coordinate of the second control point.
# @param [Integer] stroke_color The color to use for this line.
# @param [true, false] inclusive Whether to draw the last pixel.
# Set to false when drawing multiplelines in a path.
# @return [ChunkyPNG::Canvas] Itself, with the line drawn.
def line_xiaolin_wu(x0, y0, x1, y1, stroke_color, inclusive = true)
stroke_color = ChunkyPNG::Color.parse(stroke_color)
dx = x1 - x0
sx = dx < 0 ? -1 : 1
dx *= sx
dy = y1 - y0
sy = dy < 0 ? -1 : 1
dy *= sy
if dy == 0 # vertical line
x0.step(inclusive ? x1 : x1 - sx, sx) do |x|
compose_pixel(x, y0, stroke_color)
end
elsif dx == 0 # horizontal line
y0.step(inclusive ? y1 : y1 - sy, sy) do |y|
compose_pixel(x0, y, stroke_color)
end
elsif dx == dy # diagonal
x0.step(inclusive ? x1 : x1 - sx, sx) do |x|
compose_pixel(x, y0, stroke_color)
y0 += sy
end
elsif dy > dx # vertical displacement
compose_pixel(x0, y0, stroke_color)
e_acc = 0
e = ((dx << 16) / dy.to_f).round
(dy - 1).downto(0) do |i|
e_acc_temp, e_acc = e_acc, (e_acc + e) & 0xffff
x0 += sx if (e_acc <= e_acc_temp)
w = 0xff - (e_acc >> 8)
compose_pixel(x0, y0, ChunkyPNG::Color.fade(stroke_color, w))
compose_pixel(x0 + sx, y0 + sy, ChunkyPNG::Color.fade(stroke_color, 0xff - w)) if inclusive || i > 0
y0 += sy
end
compose_pixel(x1, y1, stroke_color) if inclusive
else # horizontal displacement
compose_pixel(x0, y0, stroke_color)
e_acc = 0
e = ((dy << 16) / dx.to_f).round
(dx - 1).downto(0) do |i|
e_acc_temp, e_acc = e_acc, (e_acc + e) & 0xffff
y0 += sy if (e_acc <= e_acc_temp)
w = 0xff - (e_acc >> 8)
compose_pixel(x0, y0, ChunkyPNG::Color.fade(stroke_color, w))
compose_pixel(x0 + sx, y0 + sy, ChunkyPNG::Color.fade(stroke_color, 0xff - w)) if inclusive || i > 0
x0 += sx
end
compose_pixel(x1, y1, stroke_color) if inclusive
end
return self
end
alias_method :line, :line_xiaolin_wu
# Draws a polygon on the canvas using the stroke_color, filled using the fill_color if any.
#
# @param [Array, String] The control point vector. Accepts everything {ChunkyPNG.Vector} accepts.
# @param [Integer] stroke_color The stroke color to use for this polygon.
# @param [Integer] fill_color The fill color to use for this polygon.
# @return [ChunkyPNG::Canvas] Itself, with the polygon drawn.
def polygon(path, stroke_color = ChunkyPNG::Color::BLACK, fill_color = ChunkyPNG::Color::TRANSPARENT)
vector = ChunkyPNG::Vector(*path)
raise ArgumentError, "A polygon requires at least 3 points" if path.length < 3
stroke_color = ChunkyPNG::Color.parse(stroke_color)
fill_color = ChunkyPNG::Color.parse(fill_color)
# Fill
unless fill_color == ChunkyPNG::Color::TRANSPARENT
vector.y_range.each do |y|
intersections = []
vector.edges.each do |p1, p2|
if (p1.y < y && p2.y >= y) || (p2.y < y && p1.y >= y)
intersections << (p1.x + (y - p1.y).to_f / (p2.y - p1.y) * (p2.x - p1.x)).round
end
end
intersections.sort!
0.step(intersections.length - 1, 2) do |i|
intersections[i].upto(intersections[i + 1]) do |x|
compose_pixel(x, y, fill_color)
end
end
end
end
# Stroke
vector.each_edge do |(from_x, from_y), (to_x, to_y)|
line(from_x, from_y, to_x, to_y, stroke_color, false)
end
return self
end
# Draws a rectangle on the canvas, using two control points.
#
# @param [Integer] x0 The x-coordinate of the first control point.
# @param [Integer] y0 The y-coordinate of the first control point.
# @param [Integer] x1 The x-coordinate of the second control point.
# @param [Integer] y1 The y-coordinate of the second control point.
# @param [Integer] stroke_color The line color to use for this rectangle.
# @param [Integer] fill_color The fill color to use for this rectangle.
# @return [ChunkyPNG::Canvas] Itself, with the rectangle drawn.
def rect(x0, y0, x1, y1, stroke_color = ChunkyPNG::Color::BLACK, fill_color = ChunkyPNG::Color::TRANSPARENT)
stroke_color = ChunkyPNG::Color.parse(stroke_color)
fill_color = ChunkyPNG::Color.parse(fill_color)
# Fill
unless fill_color == ChunkyPNG::Color::TRANSPARENT
[x0, x1].min.upto([x0, x1].max) do |x|
[y0, y1].min.upto([y0, y1].max) do |y|
compose_pixel(x, y, fill_color)
end
end
end
# Stroke
line(x0, y0, x0, y1, stroke_color, false)
line(x0, y1, x1, y1, stroke_color, false)
line(x1, y1, x1, y0, stroke_color, false)
line(x1, y0, x0, y0, stroke_color, false)
return self
end
# Draws a circle on the canvas.
#
# @param [Integer] x0 The x-coordinate of the center of the circle.
# @param [Integer] y0 The y-coordinate of the center of the circle.
# @param [Integer] radius The radius of the circle from the center point.
# @param [Integer] stroke_color The color to use for the line.
# @param [Integer] fill_color The color to use that fills the circle.
# @return [ChunkyPNG::Canvas] Itself, with the circle drawn.
def circle(x0, y0, radius, stroke_color = ChunkyPNG::Color::BLACK, fill_color = ChunkyPNG::Color::TRANSPARENT)
stroke_color = ChunkyPNG::Color.parse(stroke_color)
fill_color = ChunkyPNG::Color.parse(fill_color)
f = 1 - radius
ddF_x = 1
ddF_y = -2 * radius
x = 0
y = radius
compose_pixel(x0, y0 + radius, stroke_color)
compose_pixel(x0, y0 - radius, stroke_color)
compose_pixel(x0 + radius, y0, stroke_color)
compose_pixel(x0 - radius, y0, stroke_color)
lines = [radius - 1] unless fill_color == ChunkyPNG::Color::TRANSPARENT
while x < y
if f >= 0
y -= 1
ddF_y += 2
f += ddF_y
end
x += 1
ddF_x += 2
f += ddF_x
unless fill_color == ChunkyPNG::Color::TRANSPARENT
lines[y] = lines[y] ? [lines[y], x - 1].min : x - 1
lines[x] = lines[x] ? [lines[x], y - 1].min : y - 1
end
compose_pixel(x0 + x, y0 + y, stroke_color)
compose_pixel(x0 - x, y0 + y, stroke_color)
compose_pixel(x0 + x, y0 - y, stroke_color)
compose_pixel(x0 - x, y0 - y, stroke_color)
unless x == y
compose_pixel(x0 + y, y0 + x, stroke_color)
compose_pixel(x0 - y, y0 + x, stroke_color)
compose_pixel(x0 + y, y0 - x, stroke_color)
compose_pixel(x0 - y, y0 - x, stroke_color)
end
end
unless fill_color == ChunkyPNG::Color::TRANSPARENT
lines.each_with_index do |length, y|
line(x0 - length, y0 - y, x0 + length, y0 - y, fill_color) if length > 0
line(x0 - length, y0 + y, x0 + length, y0 + y, fill_color) if length > 0 && y > 0
end
end
return self
end
end
end
end