EdgeDetection.jl

# # Imports
using Pkg
Pkg.activate(".");

using Plots
using TiffImages

# # Load Image and convert to grayscale
img = TiffImages.load("MD/image3.tiff");
img = Float64.(Gray.(img))*255;

rows   = size(img, 1);
cols   = size(img, 2);

# # Gray Scale Image Input
p1 = Plots.heatmap(reverse(img, dims=1))

# # Edge Detection

# The Sobel operator is applied for edge detection.


ximage = zeros(rows,cols);
yimage = zeros(rows,cols);
simage = zeros(rows,cols);
bimage = zeros(rows,cols);


maxim = zeros(Float32,3);
maxim[1] = 0;
maxim[2] = 0;
maxim[3] = 0;
# Calculate sobel mask for ∂E/∂x and ∂E/∂y & calculate the square gradient magnitude (edge strength)

for i in 2:rows-1
    for j in 2:cols-1
        
        gx = abs(
            -img[i-1, j-1] - 2*img[i, j-1] - img[i+1, j-1] + img[i-1, j+1] +  2*img[i, j+1] + img[i+1, j+1])
        maxim[1] = max(gx, maxim[1])
        ximage[i, j] = gx

        gy = abs(-img[i-1, j-1] -2*img[i-1, j] - img[i-1, j+1] + img[i+1, j-1] + 2*img[i+1, j] + img[i+1, j+1])
        maxim[2] = max(gy, maxim[2])
        yimage[i, j] = gy
        
        sgm = sqrt(gx^2 + gy^2)
        maxim[3] = max(sgm, maxim[3])
        simage[i, j] = sgm
    end
end

# Normalize the images between 0 and 255
ximage .= ximage .* (255 / maxim[1])
yimage .= yimage .* (255 / maxim[2])
simage .= simage .* (255 / maxim[3])
Plots.heatmap(reverse(simage, dims = 1))

# Create binary image of edge map
for i in 1:rows
    for j in 1:cols
        if simage[i, j] > 45
            bimage[i, j] = 255
        else
            bimage[i, j] = 0
        end
    end
end

# # View the X and Y gradient images
l = @layout [a b] 
p2 = Plots.plot(
    Plots.heatmap(reverse(ximage, dims=1), color=:grays),
    Plots.heatmap(reverse(yimage, dims=1), color=:grays),
    layout = l,
    size=(1200, 400)
)

# # View the edge map
p3 = Plots.heatmap(reverse(simage, dims = 1))

# # View the binary image
p4 = Plots.heatmap(reverse(bimage, dims = 1))

# # Save the images
using ImageMagick

simage = round.(UInt8, simage)
bimage = convert.(UInt8, bimage)
ImageMagick.save("sgm.ras", simage)
ImageMagick.save("binaryimg.ras", bimage)