Add functions for extracting data.

Because
* We need them in a package for convenience.

Only linear and log axis are supported for the moment.

src/VectorPlotDigitizer.jl

@@ -1,15 +1,9 @@
 module VectorPlotDigitizer
 
-# Write your package code here.
-export hellow_orld
+using DelimitedFiles
 
-"""
-    hellow_orld()
+export calibrate_axis, extract_svgpath
 
-This function is for testing purposes. I want to see if the package structure works.
-"""
-function hellow_orld()
-    print("Hellow, olrd!")
-end
+include("core_functions.jl")
 
-end
+end # module

src/core_functions.jl

@@ -0,0 +1,125 @@
+function rel2abs_coordinates(data)
+    # Permutate the matrix for faster processing
+    data_perm = permutedims(data)
+    # Transform the data
+    ix = axes(data_perm,2)
+    for i in ix[(begin+1):end]
+        data_perm[:,i] += data_perm[:,i-1]
+    end
+    # Transpose again
+    return permutedims(data_perm)
+end
+
+function axis_units(x0_path, x1_path, x0_real, x1_real)
+    # Compute the distance between the path points
+    Δx_path = x1_path - x0_path
+    Δx_real = x1_real - x0_real
+    # Compute how many real units are one path unit
+    units = Δx_real / Δx_path
+
+    return units
+end
+
+function calibrate_axis(l_path, l_real; is_xaxis_log = false, is_yaxis_log = false, is_yinverted = false)
+    # Read the L path coordinates by creating a temporary file
+    outfile = "l_coords.txt"
+    extract_svgpath(l_path, outfile)
+    # Read file contents as a Matrix
+    l_path = readdlm(outfile, ',', Float64, '\n')
+    # Delete file
+    rm(outfile)
+    # Convert to absolute coordinates
+    l_path = rel2abs_coordinates(l_path)
+
+    # Compute points of the transformation
+    xp0 = l_path[2,1]
+    xp1 = l_path[3,1]
+    yp0 = l_path[2,2]
+    yp1 = l_path[1,2]
+    # If axis is log, transform the real coordinates to the exp10 exponents
+    if is_xaxis_log
+        xr0 = log10(l_real[2,1])
+        xr1 = log10(l_real[3,1])
+    else
+        xr0 = l_real[2,1]
+        xr1 = l_real[3,1]
+    end
+    if is_yaxis_log
+        yr0 = log10(l_real[2,2])
+        yr1 = log10(l_real[1,2])
+    else
+        yr0 = l_real[2,2]
+        yr1 = l_real[1,2]
+    end
+
+    # Compute x and y axis units
+    x_axis_units = axis_units(xp0, xp1, xr0, xr1)
+    y_axis_units = axis_units(yp0, yp1, yr0, yr1)
+    # Create options dictionary to be read by the transforming function
+    options = Dict("xunits" => x_axis_units, "yunits" => y_axis_units,
+    "xp0" => xp0, "xr0" => xr0, "yp0" => yp0, "yr0" => yr0,
+    "isxlog" => is_xaxis_log, "isylog" => is_yaxis_log, "isyinverted" => is_yinverted
+    )
+    return options
+end
+
+
+function extract_svgpath(input_str::AbstractString, outfile::String)
+    # Split string in each space
+    str_splitted = split(input_str, ' ')
+
+    open(outfile, "w") do f
+        case = "m" # Command m, l, h or v of the SVG path
+        for s in str_splitted # Loop everything and decide
+            if occursin(s, "mlhv")
+                case = s
+            else
+                if case == "m" || case == "l"
+                    line = s
+                elseif case == "h"
+                    line = s * ",0.0"
+                elseif case == "v"
+                    line = "0.0," * s
+                end
+
+                write(f, line * "\n")
+            end
+        end
+    end
+end
+
+function extract_svgpath(input_str::AbstractString, outfile::String, options::Dict)
+    # Transform svg path to txt first
+    tempfile = outfile * "_tmp"
+    extract_svgpath(input_str, tempfile)
+    # Read data
+    data = readdlm(tempfile, ',', Float64, '\n')
+    # Delete file
+    rm(tempfile)
+    # Obtain units and points from options dictionary
+    xunits = opts["xunits"]
+    yunits = opts["yunits"]
+    xr0 = opts["xr0"]
+    xp0 = opts["xp0"]
+    yr0 = opts["yr0"]
+    yp0 = opts["yp0"]
+    # Convert data to absolute coordinates
+    data = rel2abs_coordinates(data)
+    # Change path units to real units
+    data[:,1] .= (data[:,1] .- xp0) .* xunits .+ xr0
+    data[:,2] .= (data[:,2] .- yp0) .* yunits .+ yr0
+    # If axis scale is log, we have obtained the exponents of the base 10. Exponentiate
+    if opts["isxlog"]
+        data = exp10.(data[:,1])
+    end
+    if opts["isylog"]
+        data[:,2] .= exp10.(data[:,2])
+    end
+    # ! The minus sign is automatically incorporated as long as the data and the L coordinates of the axis
+    # ! follow the same criteria of svg path. DON'T MIX THEM!
+
+    # Save file
+    open(outfile, "w") do f
+        writedlm(f, data, ',')
+    end
+end