Images

Placing images

There is some limited support for placing PNG images on the drawing. First, load a PNG image using readpng(filename).

Then use placeimage() to place it by its top left corner at point x/y or pt. Access the image's dimensions with .width and .height.

img = readpng("assets/figures/julia-logo-mask.png")
w = img.width
h = img.height
rulers()
scale(0.3, 0.3)
rotate(π/4)
placeimage(img, -w/2, -h/2, .5)
sethue("red")
circle(-w/2, -h/2, 15, :fill)

readpng(pathname)

image = readpng("/tmp/test-image.png")
w = image.width
h = image.height

placeimage(img, xpos, ypos; centered=false)

placeimage(img, pos; centered=false)

placeimage(img, xpos, ypos, a; centered=false)

placeimage(img, pos, a; centered=false)

Clipping images

You can clip images. The following script repeatedly places the image using a circle to define a clipping path:

using Luxor

width, height = 4000, 4000
margin = 500

fname = "/tmp/test-image.pdf"
Drawing(width, height, fname)
origin()
background("grey25")

setline(5)
sethue("green")

image = readpng(dirname(@__FILE__) * "assets/figures/julia-logo-mask.png")

w = image.width
h = image.height

pagetiles = Tiler(width, height, 7, 9)
tw = pagetiles.tilewidth/2
for (pos, n) in pagetiles
    circle(pos, tw, :stroke)
    circle(pos, tw, :clip)
    gsave()
    translate(pos)
    scale(.95, .95)
    rotate(rand(0.0:π/8:2π))
    placeimage(image, O, centered=true)
    grestore()
    clipreset()
end

finish()

Transforming images

You can transform images by setting the current matrix, either with scale() and rotate() and similar, or by modifying it directly. This code skews an image made in an earlier chapter of this document and scales and rotates it in a circle:

img = readpng(dirname(dirname(pathof(Luxor))) * "/docs/src/assets/figures/textoutlines.png")
w = img.width
h = img.height
for θ in 0:π/6:2π-π/6
    gsave()
    scale(.4, .4)
    rotate(θ)
    translate(300, 0)
    placeimage(img, -w/2, -h/2, 0.9)
    grestore()
end

Drawing on images

You sometimes want to draw over images, for example to annotate them with text or vector graphics. The things to be aware of are mostly to do with coordinates and transforms.

In these examples, we'll annotate a PNG file.

image = readpng("assets/figures/julia-logo-mask.png")

w = image.width
h = image.height

# create a drawing surface of the same size

fname = "assets/figures/drawing_on_images.png"
Drawing(w, h, fname)

# place the image on the Drawing - it's positioned by its top/left corner

placeimage(image, 0, 0)

# now you can annotate the image. The (0/0) is at the top left.

sethue("red")
setline(1)
fontsize(16)
circle(Point(150, 50), 2, :fill)
label("(150/50)", :NE, Point(150, 50), leader=true, offset=25)

arrow(Point(w/2, 90), Point(0, 90))
arrow(Point(w/2, 90), Point(w, 90))
text("width $w", Point(w/2, 70), halign=:center)

# to divide up the image into rectangular areas and number them,
# temporarily position the axes at the center:

@layer begin
  setline(0.5)
  sethue("green")
  fontsize(12)
  translate(w/2, h/2)
  tiles = Tiler(w, h, 8, 8, margin=0)
  for (pos, n) in tiles
      box(pos, tiles.tilewidth, tiles.tileheight, :stroke)
      text(string(n-1), pos, halign=:center)
  end
end

Adding text to transformed images

The above approach works well, but suppose you want to locate the working origin at the lower left of the image, ie you want all coordinates to be relative to the bottom left corner of the image?

To do this, use translate() and transform() to modify the drawing space:

image = readpng("assets/figures/julia-logo-mask.png")
w = image.width
h = image.height
fname = "assets/figures/drawing_on_images_2.png"
Drawing(w, h, fname)
placeimage(image, 0, 0)

# Move the axes to the bottom:

translate(0, h)

# and reflect in the x-axis

transform([1 0 0 -1 0 0])

# now 0/0 is at the bottom left corner, and 100/100 is up and to the right.

sethue("blue")
arrow(Point(200, 300), Point(160, 300))

# However, don't draw text while flipped, because it will be reversed!

fontsize(20)
sethue("black")
text("Oh no!", Point(30, 250))

# To work around this, define a text function
# that flips the workspace over the x-axis just for the text:

function textoverlay(t, pos; kwargs...)
    @layer begin
        translate(pos)
        transform([1 0 0 -1 0 0])
        text(t, O; kwargs...)
    end
end

textoverlay("a tittle!", Point(200, 300), halign=:left, valign=:middle)
textoverlay("0/0", O)
arrow(Point(130, 400), Point(130, 340))

Image compositing

You should be using Images.jl for most tasks involving image editing. But if you just need to composite images together, you can use the blending modes provided by setmode().

img = readpng("assets/figures/textoutlines.png")
w = img.width
h = img.height

placeimage(img, -w/2, -h/2, .5)
setmode("saturate")
translate(50, 0)
placeimage(img, -w/2, -h/2, .5)