# Placing images

Luxor lets you place existing PNG and SVG images on the drawing. First, load the image:

• for PNG images, use readpng(filename)
• for SVG images, use readsvg(filename) or readsvg(string)

(JPEGs aren't supported.)

Then use placeimage to place the image by its top left corner at point pt, or use the centered=true keyword to place the image's center point there. 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, Point(-w/2, -h/2), .5)
sethue("red")
circle(-w/2, -h/2, 15, :fill)

PNG images can be placed with varying opacity or transparency.

readsvg also lets you supply raw (or pure) SVG code in a string.

You can also use placeimage() to place an array of RGB or RGBA pixels on a drawing.

N = 500
i = reshape([RGBA(rand(4)...) for p in 1:N^2], N, N)
# is is Matrix{RGBA{Float64}}
# (alias for Array{RGBA{Float64}, 2})
@draw begin
origin()
sethue("orange")
box(O, N/2, N/2, :fill)
placeimage(i, O, centered=true, alpha=0.5)
end 500 500

Or load an image as an array and place it on a drawing.

using Luxor, Colors, FileIO
@draw begin
img[1:50, :] .= colorant"cyan"
img[200:end, :] .= colorant"magenta"
placeimage(img, O, centered=true, alpha=0.5)
end 250 250

## SVG images

To create an SVG image, using the Drawing(... :svg) or specify an SVG filename. To obtain the SVG source of a completed drawing, use svgstring.

For example, draw the Julia logo:

Drawing(500, 500, :svg)
origin()
julialogo()
finish()
s = svgstring()

The SVG source code is now stored in s. You can examine or process it further:

eachmatch(r"rgb\$$.*?\$$", s) |> collect
5-element Vector{RegexMatch}:
RegexMatch("rgb(0%,0%,0%)")
RegexMatch("rgb(79.6%,23.5%,20%)")
RegexMatch("rgb(25.1%,38.8%,84.7%)")
RegexMatch("rgb(58.4%,34.5%,69.8%)")
RegexMatch("rgb(22%,59.6%,14.9%)")

To display the image in a Jupyter or Pluto notebook, use the HTML function, or you can use the readsvg and placeimage functions in combination.

## Placing an image matrix

You can also use placeimage to put image matrices on a drawing.

using Luxor

mat = @imagematrix begin
juliacircles(6)
end 40 40

@draw begin
for i in 1:500
pos = rand(BoundingBox())
@layer begin
translate(pos)
rotate(rand() * 2π)
placeimage(mat, centered = rand(Bool))
end
end
end

placeimage can also take in an optional argument alpha to change the opacity of the image matrix.

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

setline(5)
sethue("green")

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 scales and rotates an image made in an earlier chapter of this document around 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

## Combining images and vector graphics

You sometimes want to combine vector graphics and images, for example, to annotate them with text or vector graphics.

There are two ways you can do this:

• by adding the image with placeimage() and then drawing vector graphics on top.

• by opening the image as a drawing, and adding vector graphics into the image.

The things to be aware of are mostly to do with coordinates and transforms.

In this example, 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 placed images

The above approach works well, but suppose you want to locate the working origin at the lower left of the image, i.e. 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))

### Opening the image as drawing

An alternative way to work with images is to open the image as a drawing. Let's open the well-known mandrill image in Luxor. (I'll call him Marvin, because I couldn't find out whether or not the model had a name, but I think he should have one.)

using Luxor, Colors, Images, TestImages

marvin = testimage("mandrill")
M = Luxor.Colors.ARGB32.(marvin)
Drawing(M)

The current drawing is now a 512 × 512 array, where each pixel is an ARGB32 (an unsigned 32-bit integer holding 4 8-bit vaalues).

Marvin's right eye (on the left side of the drawing) is located at about 60 rows down, 175 columns across. Let's fill in his pupil with a white square:

M[55:65, 170:180] .= colorant"white"
M

Using M on its own should show the image in your notebook or code editor (but not the REPL). If you want to save it, using the standard Images.jl functions.

We can use these indices as x and y coordinates, since the drawing origin is also currently at the top left.

sethue("white")
circle(Point(60, 175), 20, :stroke)
M

If we want to draw, say, a 10 by 10 numbered grid overlay on top of Marvin, and highlight four numbered cells, it's easier to just add a transform() function that flips the x/cols and y/rows convention, then create a table centered at the center of the drawing:

fontsize(15)
sethue("white")
setline(1)
transform([0 1 1 0 0 0])
cells = Table(10, 10, 512 / 10, 512 / 10, Point(512 / 2, 512 / 2))
for (pos, n) in cells
text(string(n), pos, halign = :center, valign = :middle)
box(pos, 512 / 10, 512 / 10, :stroke)
end
setline(5)
highlightcells(cells, collect(1:100)[[2, 4, 35, 69]], :stroke,
color = colorant"blue")
M

## 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)