Brief tutorial: visualizing page layout

MiseEnPage includes high-level functions for retrieving a documentary image for a page, and for diagramming page layout data using the Luxor graphics package. These functions make it straightforward to visualize the layout problem and analysis.

Documentary image

Continuing with the example page from the preceding documentation, we can load a documentary image for a page with the load_rgba function. Optional parameters let you scale the resulting image to a given width (w), and to set the alpha channel of the image (on a scale of 0.0 to 1.0).

img = load_rgba(pg; w = 200, alpha = 0.4)

In Julia, an image is just a normal Julia matrix of pixel values (here, RGBA values).

img |> typeof

Matrix{RGBA{N0f8}} (alias for Array{ColorTypes.RGBA{FixedPointNumbers.Normed{UInt8, 8}}, 2})

MiseEnPage includes a convenience function to save the width and height of the image in a named tuple.

dimm = dimensions(img)

(h = 266, w = 200)

Diagramming page layout with Luxor

Luxor includes shorthand macros to create diagrams as files on disk (e.g., @png) or for display in an interactive environment (@draw). You can specify a width and height for the resulting image following the macro's begin..end block. This boilerplate code uses the dimensions we just saved to create a drawing space of the same dimensions as our image.

using Luxor
# Boilerplate framework:
@draw begin


end dimm[:w] dimm[:h]

Next, we'll use two standard Luxor functions to place the image in the drawing space, translate and placeimage. By default, Luxor places the coordinate origin at the center of the drawing space, but's easier to draw on the image if we align the coordinate system's origin (0,0) to be the top left corner of the space. We can do that by shifting the origin up and to the left (both negative directions) for one half the size of our image. (That's the translate function in the following code snippet.) Then we'll place the image at the origin, here named with the Luxor shorthand O (the letter O).

@draw begin
     translate(-1 * dimm[:w]/2,  -1 * dimm[:h]/2)
     placeimage(img,O)

end dimm[:w] dimm[:h]

Now we have our image in a Luxor drawing space where we can continue our diagram. MiseEnPage includes functions you can use to add to the composition of a Luxor drawing.

• pagebox draws a rectangle around the physical page
• iliadbox draws a rectangle around the block of edited Iliad text

You can mix these in with normal Luxor functions like sethue and setline, as in the following example.

@draw begin
     translate(-1 * dimm[:w]/2,  -1 * dimm[:h]/2)
     placeimage(img,O)
     sethue("green")
     setline(2)
     pagebox_luxor(pg, img)
     sethue("blue")
     iliadbox_luxor(pg, img)
     sethue("gray")
      commented_lines_luxor(pg, img)
end dimm[:w] dimm[:h]