Colors and styles

Color and opacity

For color definitions and conversions, you can use Colors.jl.

setcolor() and sethue() will apply a single solid or transparent color to new graphics.

setblend() will apply a smooth transition between two or more colors to new graphics.

setmesh() will apply a color mesh to new graphics.

The difference between the setcolor() and sethue() functions is that sethue() is independent of alpha opacity, so you can change the hue without changing the current opacity value.

Named colors, such as "gold", or "lavender", can be found in Colors.color_names.

fontsize(8)
cols = sort(collect(Colors.color_names))
ncols = 15
nrows = convert(Int, ceil(length(cols) / ncols))
table = Table(nrows, ncols, 800/ncols, 800/nrows)
gamma = 2.2
for n in 1:length(cols)
    col = cols[n][1]
    r, g, b = sethue(col)
    box(table[n], table.colwidths[1], table.rowheights[1], :fill)
    luminance = 0.2126 * r^gamma + 0.7152 * g^gamma + 0.0722 * b^gamma
    (luminance > 0.5^gamma) ? sethue("black") : sethue("white")
    text(string(cols[n][1]), table[n], halign=:center, valign=:middle)
end

line endings

(To make the label stand out against the background, the luminance is calculated, then used to choose the label's color.)

Luxor.sethue — Function

sethue("black")
sethue(0.3, 0.7, 0.9)
setcolor(sethue("red")..., .2)

Set the color without changing opacity.

sethue() is like setcolor(), but we sometimes want to change the current color without changing alpha/opacity. Using sethue() rather than setcolor() doesn't change the current alpha opacity.

Line styles

There are set- functions for controlling subsequent lines' width, end shapes, join behavior, and dash patterns:

for l in 1:3
    sethue("black")
    setline(20)
    setlinecap(["butt", "square", "round"][l])
    textcentred(["butt", "square", "round"][l], 80l, 80)
    setlinejoin(["round", "miter", "bevel"][l])
    textcentred(["round", "miter", "bevel"][l], 80l, 120)
    poly(ngon(Point(80l, 0), 20, 3, 0, vertices=true), :strokepreserve, close=false)
    sethue("white")
    setline(1)
    strokepath()
end

line endings

patterns = ["solid", "dotted", "dot", "dotdashed", "longdashed",
  "shortdashed", "dash", "dashed", "dotdotdashed", "dotdotdotdashed"]
setline(12)

table = Table(fill(20, length(patterns)), [50, 300])
text.(patterns, table[:, 1], halign=:right, valign=:middle)

for p in 1:length(patterns)
    setdash(patterns[p])
    pt = table[p, 2]
    line(pt - (150, 0), pt + (150, 0), :stroke)
end

dashes

To define more complicated dash patterns in Luxor, supply a vector to setdash().

dashes = [50.0,  # ink
          10.0,  # skip
          10.0,  # ink
          10.0   # skip
          ]
setdash(dashes)

function dashing()
    setline(8)
    setlinecap("butt")
    patterns = [10, 4, 50, 25, 14, 100]
    table = Table(fill(20, length(patterns)), [40, 325])
    for p in 1:length(patterns)
        setdash(patterns)
        pt = table[p, 2]
        text(string(patterns), table[p, 1], halign=:right, valign=:middle)
        line(pt - (150, 0), pt + (200, 0), :stroke)
        patterns = circshift(patterns, 1)
        pop!(patterns)
    end
end

dashing()

more dashes

Notice that odd-numbered patterns flip the ink and skip numbers each time through.

Luxor.setline — Function

setline(n)

Set the line width.

Luxor.setlinecap — Function

setlinecap(s)

Set the line ends. s can be "butt" or :butt (the default), "square" or :square, or "round" or :round.

Luxor.setlinejoin — Function

setlinejoin("miter")
setlinejoin("round")
setlinejoin("bevel")

Set the line join style, or how to render the junction of two lines when stroking.

Luxor.setdash — Function

setdash("dot")

Set the dash pattern to one of: "solid", "dotted", "dot", "dotdashed", "longdashed", "shortdashed", "dash", "dashed", "dotdotdashed", "dotdotdotdashed".

Use setdash(dashes::Vector) to specify the pattern numerically.

setdash(dashes::Vector, offset=0.0)

Set the dash pattern to the values in dashes. The first number is the length of the ink, the second the gap, and so on.

The offset specifies an offset into the pattern at which the stroke begins. So an offset of 10 means that the stroke starts at dashes[1] + 10 into the pattern.

Or use setdash("dot") etc.

Luxor.fillstroke — Function

fillstroke()

Fill and stroke the current path.

Luxor.strokepath — Function

strokepath()

Stroke the current path with the current line width, line join, line cap, and dash settings. The current path is then cleared.

Luxor.fillpath — Function

fillpath()

Fill the current path according to the current settings. The current path is then cleared.

Luxor.strokepreserve — Function

strokepreserve()

Stroke the current path with current line width, line join, line cap, and dash settings, but then keep the path current.

Luxor.fillpreserve — Function

fillpreserve()

Fill the current path with current settings, but then keep the path current.

Luxor.paint — Function

paint()

Paint the current clip region with the current settings.

Luxor.do_action — Function

do_action(action)

This is usually called by other graphics functions. Actions for graphics commands include :fill, :stroke, :clip, :fillstroke, :fillpreserve, :strokepreserve, :none, and :path.

When you define blends, the location of the axes (eg the current workspace as defined by translate(), etc.), is important. In the first of the two following examples, the blend is selected before the axes are moved with translate(pos). The blend 'samples' the original location of the blend's definition.

goldblend = blend(Point(0, 0), Point(200, 0))
addstop(goldblend, 0.0,  "gold4")
addstop(goldblend, 0.25, "gold1")
addstop(goldblend, 0.5,  "gold3")
addstop(goldblend, 0.75, "darkgoldenrod4")
addstop(goldblend, 1.0,  "gold2")
setblend(goldblend)
tiles = Tiler(600, 200, 1, 5, margin=10)
for (pos, n) in tiles
    gsave()
    setblend(goldblend)
    translate(pos)
    ellipse(O, tiles.tilewidth, tiles.tilewidth, :fill)
    grestore()
end

blends 1

Outside the range of the original blend's definition, the same color is used, no matter how far away from the origin you go (there are Cairo options to change this). But in the next example, the blend is relocated to the current axes, which have just been moved to the center of the tile. The blend refers to 0/0 each time, which is at the center of shape.

goldblend = blend(Point(0, 0), Point(200, 0))
addstop(goldblend, 0.0,  "gold4")
addstop(goldblend, 0.25, "gold1")
addstop(goldblend, 0.5,  "gold3")
addstop(goldblend, 0.75, "darkgoldenrod4")
addstop(goldblend, 1.0,  "gold2")
setblend(goldblend)
tiles = Tiler(600, 200, 1, 5, margin=10)
for (pos, n) in tiles
    gsave()
    translate(pos)
    setblend(goldblend)
    ellipse(O, tiles.tilewidth, tiles.tilewidth, :fill)
    grestore()
end

blends 2

Luxor.blend — Function

blend(from::Point, to::Point)

Create an empty linear blend.

A blend is a specification of how one color changes into another. Linear blends are defined by two points: parallel lines through these points define the start and stop locations of the blend. The blend is defined relative to the current axes origin. This means that you should be aware of the current axes when you define blends, and when you use them.

To add colors, use addstop().

blend(centerpos1, rad1, centerpos2, rad2, color1, color2)

Create a radial blend.

Example:

redblue = blend(
    pos, 0,                   # first circle center and radius
    pos, tiles.tilewidth/2,   # second circle center and radius
    "red",
    "blue"
    )

blend(pt1::Point, pt2::Point, color1, color2)

Create a linear blend.

Example:

redblue = blend(pos, pos, "red", "blue")

blend(from::Point, startradius, to::Point, endradius)

Create an empty radial blend.

Radial blends are defined by two circles that define the start and stop locations. The first point is the center of the start circle, the first radius is the radius of the first circle.

A new blend is empty. To add colors, use addstop().

Luxor.addstop — Function

addstop(b::Blend, offset, col)
addstop(b::Blend, offset, (r, g, b, a))
addstop(b::Blend, offset, string)

Add a color stop to a blend. The offset specifies the location along the blend's 'control vector', which varies between 0 (beginning of the blend) and 1 (end of the blend). For linear blends, the control vector is from the start point to the end point. For radial blends, the control vector is from any point on the start circle, to the corresponding point on the end circle.

Examples:

blendredblue = blend(Point(0, 0), 0, Point(0, 0), 1)
addstop(blendredblue, 0, setcolor(sethue("red")..., .2))
addstop(blendredblue, 1, setcolor(sethue("blue")..., .2))
addstop(blendredblue, 0.5, sethue(randomhue()...))
addstop(blendredblue, 0.5, setcolor(randomcolor()...))

Using `blendadjust()`

You can use blendadjust() to modify the blend so that objects scaled and positioned after the blend was defined are rendered correctly.

setline(20)

# first line
blendgoldmagenta = blend(Point(-100, 0), Point(100, 0), "gold", "magenta")
setblend(blendgoldmagenta)
line(Point(-100, -50), Point(100, -50))
strokepath()

# second line
blendadjust(blendgoldmagenta, Point(50, 0), 0.5, 0.5)
line(O, Point(100, 0))
strokepath()

# third line
blendadjust(blendgoldmagenta, Point(-50, 50), 0.5, 0.5)
line(Point(-100, 50), Point(0, 50))
strokepath()

# fourth line
gsave()
translate(0, 100)
scale(0.5, 0.5)
setblend(blendgoldmagenta)
line(Point(-100, 0), Point(100, 0))
strokepath()
grestore()

blends adjust

The blend is defined to span 200 units, horizontally centered at 0/0. The top line is also 200 units long and centered horizontally at 0/0, so the blend is rendered exactly as you'd hope.

The second line is only half as long, at 100 units, centered at 50/0, so blendadjust() is used to relocate the blend's center to the point 50/0 and scale it by 0.5 (100/200).

The third line is also 100 units long, centered at -50/0, so again blendadjust() is used to relocate the blend's center and scale it.

The fourth line shows that you can translate and scale the axes instead of adjusting the blend, if you use setblend() again in the new scene.

Luxor.blendadjust — Function

blendadjust(ablend, center::Point, xscale, yscale, rot=0)

Modify an existing blend by scaling, translating, and rotating it so that it will fill a shape properly even if the position of the shape is nowhere near the original location of the blend's definition.

For example, if your blend definition was this (notice the 1)

blendgoldmagenta = blend(
        Point(0, 0), 0,                   # first circle center and radius
        Point(0, 0), 1,                   # second circle center and radius
        "gold",
        "magenta"
        )

you can use it in a shape that's 100 units across and centered at pos, by calling this:

blendadjust(blendgoldmagenta, Point(pos.x, pos.y), 100, 100)

then use setblend():

setblend(blendgoldmagenta)

Blending (compositing) operators

Graphics software provides ways to modify how the virtual "ink" is applied to existing graphic elements. In PhotoShop and other software products the compositing process is done using blend modes.

Use setmode() to set the blending mode of subsequent graphics.

origin()
# transparent, no background
fontsize(15)
setline(1)
tiles = Tiler(600, 600, 4, 5, margin=30)
modes = length(Luxor.blendingmodes)
setcolor("black")
for (pos, n) in tiles
    n > modes && break
    gsave()
    translate(pos)
    box(O, tiles.tilewidth-10, tiles.tileheight-10, :clip)

    # calculate points for circles
    diag = (Point(-tiles.tilewidth/2, -tiles.tileheight/2),
            Point(tiles.tilewidth/2,  tiles.tileheight/2))
    upper = between(diag, 0.4)
    lower = between(diag, 0.6)

    # first red shape uses default blend operator
    setcolor(0.7, 0, 0, .8)
    circle(upper, tiles.tilewidth/4, :fill)

    # second blue shape shows results of blend operator
    setcolor(0, 0, 0.9, 0.4)
    blendingmode = Luxor.blendingmodes[mod1(n, modes)]
    setmode(blendingmode)
    circle(lower, tiles.tilewidth/4, :fill)

    clipreset()
    grestore()

    gsave()
    translate(pos)
    text(Luxor.blendingmodes[mod1(n, modes)], O.x, O.y + tiles.tilewidth/2, halign=:center)
    grestore()
end

blend modes

Notice in this example that clipping was used to restrict the area affected by the blending process.

In Cairo these blend modes are called operators. A source for a more detailed explanation can be found here.

You can access the list of modes with the unexported symbol Luxor.blendingmodes.

Luxor.setmode — Function

setmode(mode::AbstractString)

Set the compositing/blending mode. mode can be one of:

"clear" Where the second object is drawn, the first is completely removed.
"source" The second object is drawn as if nothing else were below.
"over" The default mode: like two transparent slides overlapping.
"in" The first object is removed completely, the second is only drawn where the first was.
"out" The second object is drawn only where the first one wasn't.
"atop" The first object is mostly intact, but mixes both objects in the overlapping area. The second object object is not drawn elsewhere.
"dest" Discard the second object completely.
"dest_over" Like "over" but draw second object below the first
"dest_in" Keep the first object whereever the second one overlaps.
"dest_out" The second object is used to reduce the visibility of the first where they overlap.
"dest_atop" Like "over" but draw second object below the first.
"xor" XOR where the objects overlap
"add" Add the overlapping areas together
"saturate" Increase Saturation where objects overlap
"multiply" Multiply where objects overlap
"screen" Input colors are complemented and multiplied, the product is complemented again. The result is at least as light as the lighter of the input colors.
"overlay" Multiplies or screens colors, depending on the lightness of the destination color.
"darken" Selects the darker of the color values in each component.
"lighten" Selects the lighter of the color values in each component.

See the Cairo documentation for details.

Luxor.getmode — Function

getmode()

Return the current compositing/blending mode as a string.

Meshes

A mesh provides smooth shading between three or four colors across a region defined by lines or curves.

To create a mesh, use the mesh() function and save the result as a mesh object. To use a mesh, supply the mesh object to the setmesh() function.

The mesh() function accepts either an array of Bézier paths or a polygon.

This basic example obtains a polygon from the drawing area using box(BoundingBox()... and uses the four corners of the mesh and the four colors in the array to build the mesh. The paint() function fills the drawing.

garishmesh = mesh(
    box(BoundingBox(), vertices=true),
    ["purple", "green", "yellow", "red"])

setmesh(garishmesh)

paint()

setline(2)
sethue("white")
hypotrochoid(180, 81, 130, :stroke)

mesh 1

The next example uses a Bézier path conversion of a square as the outline of the mesh. Because the box to be filled is larger than the mesh's outlines, not all the box is filled.

setcolor("grey50")
circle.([Point(x, y) for x in -200:25:200, y in -200:25:200], 10, :fill)

bp = makebezierpath(box(O, 300, 300, vertices=true), smoothing=.4)
setline(3)
sethue("black")

drawbezierpath(bp, :stroke)
mesh1 = mesh(bp, [
    Colors.RGBA(1, 0, 0, 1),   # bottom left, red
    Colors.RGBA(1, 1, 1, 0.0), # top left, transparent
    Colors.RGB(0, 0, 1),      # top right, blue
    Colors.RGB(1, 0, 1)        # bottom right, purple
    ])
setmesh(mesh1)
box(O, 500, 500, :fillpreserve)
sethue("grey50")
strokepath()

mesh 1

The second example uses a polygon defined by ngon() as the outline of the mesh. The mesh is drawn when the path is stroked.

pl = ngon(O, 250, 3, π/6, vertices=true)
mesh1 = mesh(pl, [
    "purple",
    "green",
    "yellow"
    ])
setmesh(mesh1)
setline(180)
poly(pl, :strokepreserve, close=true)
setline(5)
sethue("black")
strokepath()

mesh 2

Luxor.mesh — Function

mesh(bezierpath::BezierPath,
     colors=Array{Colors.Colorant, 1})

Create a mesh. The first three or four elements of the supplied bezierpath define the three or four sides of the mesh shape.

The colors array define the color of each corner point. Colors are reused if necessary. At least one color should be supplied.

Use setmesh() to select the mesh, which will be used to fill shapes.

Example

@svg begin
    bp = makebezierpath(ngon(O, 50, 4, 0, vertices=true))
    mesh1 = mesh(bp, [
        "red",
        Colors.RGB(0, 1, 0),
        Colors.RGB(0, 1, 1),
        Colors.RGB(1, 0, 1)
        ])
    setmesh(mesh1)
    box(O, 500, 500, :fill)
end

mesh(points::Array{Point},
     colors=Array{Colors.Colorant, 1})

Create a mesh.

Create a mesh. The first three or four sides of the supplied points polygon define the three or four sides of the mesh shape.

The colors array define the color of each corner point. Colors are reused if necessary. At least one color should be supplied.

Example

@svg begin
    pl = ngon(O, 250, 3, pi/6, vertices=true)
    mesh1 = mesh(pl, [
        "purple",
        Colors.RGBA(0.0, 1.0, 0.5, 0.5),
        "yellow"
        ])
    setmesh(mesh1)
    setline(180)
    ngon(O, 250, 3, pi/6, :strokepreserve)
    setline(5)
    sethue("black")
    strokepath()
end

Luxor.setmesh — Function

setmesh(mesh::Mesh)

Select a mesh previously created with mesh() for filling shapes.

Masks

A simple mask function lets you use a circular or rectangular shape to control graphics that are drawn over it. mask() takes a position and a shape, and returns a value between 0 and 1 for that position, depending on its position relative to the shape.

In the first example, the gray color of each tile is determined by its location relative to the center of the masking circle (O, bw/2); the value is 1.0 at the center, and 0.0 at the circumference. The value could be used to control opacity, shape, or anything else that is relevant to graphics at a particular position.

println("generating mask.png now...")
tiles = Tiler(600, 600, 15, 15, margin=0)
bw = boxwidth(BoundingBox())
for (pos, n) in tiles
    setgray(mask(pos, O, bw/2))
    box(pos, tiles.tilewidth, tiles.tileheight, :fillstroke)
end

sethue("white")
circle(O, bw/2, :stroke)

generating mask.png now...

mask

The second example uses the distance of each tile relative to the rectangle O, bw, bw to determine the gray color.

tiles = Tiler(600, 600, 30, 30)

bw = boxwidth(BoundingBox())
bh = boxheight(BoundingBox())
for (pos, n) in tiles
    mv = mask(pos, O, bw, bh, easingfunction=easeinoutcubic)
    setgray(mv)
    box(pos, tiles.tilewidth, tiles.tileheight, :fillstroke)
end

mask1

Luxor.mask — Function

mask(point::Point, focus::Point, radius)
    max = 1.0,
    min = 0.0,
    easingfunction = easingflat)

Calculate a value between 0 and 1 for a point relative to a circular area defined by focus and radius. The value will approach max (1.0) at the center of the circular area, and min (0.0) at the circumference.

mask(point::Point, focus::Point, width, height)
    max = 1.0,
    min = 0.0,
    easingfunction = easingflat)

Calculate a value between 0 and 1 for a point relative to a rectangular area defined by focus, width, and height. The value will approach max (1.0) at the center, and min (0.0) at the edges.