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(pi/4)
placeimage(img, -w/2, -h/2, .5)
sethue("red")
circle(-w/2, -h/2, 15, :fill)

┌ Warning: The function `cfunction` is now written as a macro `@cfunction`.
│   caller = get_stream_callback at Cairo.jl:145 [inlined]
└ @ Core Cairo.jl:145

"Images"

Luxor.readpng — Function.

readpng(pathname)

Read a PNG file.

This returns a image object suitable for placing on the current drawing with placeimage(). You can access its width and height fields:

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

source

Luxor.placeimage — Function.

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

Place a PNG image on the drawing at (xpos/ypos). The image img has been previously loaded using readpng().

Use keyword centered=true to place the center of the image at the position.

source

placeimage(img, pos; centered=false)

Place the top left corner of the PNG image on the drawing at pos.

Use keyword centered=true to place the center of the image at the position.

source

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

Place a PNG image on the drawing at (xpos/ypos) with transparency a.

Use keyword centered=true to place the center of the image at the position.

source

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

Place a PNG image on the drawing at pos with transparency a.

Use keyword centered=true to place the center of the image at the position.

source

Clipping images

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

"Images"

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:pi/8:2pi))
    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 the image and scales and rotates it in a circle:

img = readpng("assets/figures/clipping-tests.png")
w = img.width
h = img.height
for theta in 0:pi/6:2pi
    gsave()
        scale(.5, .5)
        rotate(theta)
        transform([1, 0, -pi/4, 1, 250, 0])
        placeimage(img, -w/2, -h/2, .75)
    grestore()
end

┌ Warning: The function `cfunction` is now written as a macro `@cfunction`.
│   caller = get_stream_callback at Cairo.jl:145 [inlined]
└ @ Core Cairo.jl:145

transforming images

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 this example, we'll annotate a PNG file with some text and graphics.

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")
fontsize(20)
circle(5, 5, 2, :fill)
text("(5/5)", Point(25, 25), halign=:center)

arrow(Point(w/2, 50), Point(0, 50))
arrow(Point(w/2, 50), Point(w, 50))
text("width $w", Point(w/2, 70), halign=:center)

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

gsave()
setline(0.2)
sethue("green")
fontsize(12)
translate(w/2, h/2)
tiles = Tiler(w, h, 16, 10, margin=0)
for (pos, n) in tiles
    box(pos, tiles.tilewidth, tiles.tileheight, :stroke)
    text(string(n), pos, halign=:center)
end
grestore()

# If you want coordinates to be relative to the bottom left corner of the image, transform:

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(O, Point(100, 100))

# However, don't use text while flipped, because it's reversed:

text("I'm in reverse!", w/2, h/2)

┌ Warning: The function `cfunction` is now written as a macro `@cfunction`.
│   caller = get_stream_callback at Cairo.jl:145 [inlined]
└ @ Core Cairo.jl:145

drawing on images

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/textcurvecenteredexample.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)

┌ Warning: The function `cfunction` is now written as a macro `@cfunction`.
│   caller = get_stream_callback at Cairo.jl:145 [inlined]
└ @ Core Cairo.jl:145

transforming images