Placing images
Loading and placing PNG and SVG 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)
orreadsvg(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
img = load(dirname(dirname(pathof(Luxor))) * "/docs/src/assets/figures/42.png")
@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")
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 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.
Adding graphics on top
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)