How to create julia color scheme for displaying Ct scan Makie.jl - plot

Question

I use makie.jl with slicesNumb for visualization of PET/CT scans, I have 3d array of attenuation values and I display heatmap with changing slices using slider - this works well I have two problems
I do not know how to be able to define custom colormaps (basically I need to be able to specify that all above some threshold value will be black and all below white and values between will have grey values proportional to attenuation value).
2)I would like to be able to display to display over my image (tachnically heatmap) another ones where I would be able to controll transparency - alpha value of pixels - in order to display some annotations/ PET ...
code that works but without those 2 functionalities and how it looks
using GLMakie
```#doc
simple display of single image - only in transverse plane
```
function singleCtScanDisplay(arr ::Array{Number, 3})
fig = Figure()
sl_x = Slider(fig[2, 1], range = 1:1:size(arr)[3], startvalue = 40)
ax = Axis(fig[1, 1])
hm = heatmap!(ax, lift(idx-> arr[:,:, floor(idx)], sl_x.value) ,colormap = :grays)
Colorbar(fig[1, 2], hm)
fig
end
Thanks for help !

Answer 1

You can use Colors and ColorSchemeTools, but you will need to add the top and bottom of the scheme according to your thresholds.
using Colors, ColorSchemeTools
truemin = 0
truemax = 600
max_shown_black = 20
min_shown_white = 500
data = rand(truemin:truemax, (500, 500, 20))
grayscheme = [fill(colorant"black", max_shown_black - truemin + 1);
collect(make_colorscheme(identity, identity, identity,
length = min_shown_white - max_shown_black - 1));
fill(colorant"white", truemax - min_shown_white + 1)]
For controlling alpha, I would add a popup window with an alpha slider. Take a look at some of the distributable DICOM tools for examples.

Answer 2

I finally managed it basically I load 3 dimensional data stored in hdf5 (I loaded it into hdf5 from raw using python)
It enables viewing transverse slices and annotate 3d pathes in a mask that will be displayed over main image
exmpleH = #spawnat persistenceWorker Main.h5manag.getExample()
minimumm = -1000
maximumm = 2000
arrr= fetch(exmpleH)
imageDim = size(arrr)
using GLMakie
maskArr = Observable(BitArray(undef, imageDim))
MyImgeViewer.singleCtScanDisplay(arrr, maskArr,minimumm, maximumm)
Now definition of the required modules
```#doc
functions responsible for displaying medical image Data
```
using DrWatson
#quickactivate "Probabilistic medical segmentation"
module MyImgeViewer
using GLMakie
using Makie
#using GeometryBasics
using GeometricalPredicates
using ColorTypes
using Distributed
using GLMakie
using Main.imageViewerHelper
using Main.workerNumbers
## getting id of workers
```#doc
simple display of single image - only in transverse plane we are adding also a mask that
arrr - main 3 dimensional data representing medical image for example in case of CT each voxel represents value of X ray attenuation
minimumm, maximumm - approximately minimum and maximum values we can have in our image
```
function singleCtScanDisplay(arrr ::Array{Number, 3}, maskArr , minimumm, maximumm)
#we modify 2 pixels just in order to make the color range constant so slices will be displayed in the same windows
arrr[1,1,:].= minimumm
arrr[2,1,:].= maximumm
imageDim = size(arrr) # dimenstion of the primary image for example CT scan
slicesNumb =imageDim[3] # number of slices
#defining layout variables
scene, layout = GLMakie.layoutscene(resolution = (600, 400))
ax1 = layout[1, 1] = GLMakie.Axis(scene, backgroundcolor = :transparent)
ax2 = layout[1, 1] = GLMakie.Axis(scene, backgroundcolor = :transparent)
#control widgets
sl_x =layout[2, 1]= GLMakie.Slider(scene, range = 1:1: slicesNumb , startvalue = slicesNumb/2 )
sliderXVal = sl_x.value
#color maps
cmwhite = cgrad(range(RGBA(10,10,10,0.01), stop=RGBA(0,0,255,0.4), length=10000));
greyss = createMedicalImageColorSchemeB(200,-200,maximumm, minimumm )
####heatmaps
#main heatmap that holds for example Ct scan
currentSliceMain = GLMakie.#lift(arrr[:,:, convert(Int32,$sliderXVal)])
hm = GLMakie.heatmap!(ax1, currentSliceMain ,colormap = greyss)
#helper heatmap designed to respond to both changes in slider and changes in the bit matrix
currentSliceMask = GLMakie.#lift($maskArr[:,:, convert(Int32,$sliderXVal)])
hmB = GLMakie.heatmap!(ax1, currentSliceMask ,colormap = cmwhite)
#adding ability to be able to add information to mask where we clicked so in casse of mit matrix we will set the point where we clicked to 1
indicatorC(ax1,imageDim,scene,maskArr,sliderXVal)
#displaying
colorB = layout[1,2]= Colorbar(scene, hm)
GLMakie.translate!(hmB, Vec3f0(0,0,5))
scene
end
```#doc
inspired by https://github.com/JuliaPlots/Makie.jl/issues/810
Generaly thanks to this function the viewer is able to respond to clicking on the slices and records it in the supplied 3 dimensional AbstractArray
ax - Axis which store our heatmap slices which we want to observe wheather user clicked on them and where
dims - dimensions of main image for example CT
sc - Scene where our axis is
maskArr - the 3 dimensional bit array that has exactly the same dimensions as main Array storing image
sliceNumb - represents on what slide we are on currently on - ussually it just give information from slider
```
function indicatorC(ax::Axis,dims::Tuple{Int64, Int64, Int64},sc::Scene,maskArr,sliceNumb::Observable{Any})
register_interaction!(ax, :indicator) do event::GLMakie.MouseEvent, axis
if event.type === MouseEventTypes.leftclick
println("clicked")
##async begin
#appropriately modyfing wanted pixels in mask array
#async calculateMouseAndSetmaskWrap(maskArr, event,sc,dims,sliceNumb)
#
#
# println("fetched" + fetch(maskA))
# finalize(maskA)
#end
return true
#print("xMouse: $(xMouse) yMouse: $(yMouse) compBoxWidth: $(compBoxWidth) compBoxHeight: $(compBoxHeight) calculatedXpixel: $(calculatedXpixel) calculatedYpixel: $(calculatedYpixel) pixelsNumbInX $(pixelsNumbInX) ")
end
end
end
```#doc
wrapper for calculateMouseAndSetmask - from imageViewerHelper module
given mouse event modifies mask accordingly
maskArr - the 3 dimensional bit array that has exactly the same dimensions as main Array storing image
event - mouse event passed from Makie
sc - scene we are using in Makie
```
function calculateMouseAndSetmaskWrap(maskArr, event,sc,dims,sliceNumb)
maskArr[] = calculateMouseAndSetmask(maskArr, event,sc,dims,sliceNumb)
end
end #module
and helper methods
```#doc
functions responsible for helping in image viewer - those functions are meant to be invoked on separate process
- in parallel
```
using DrWatson
#quickactivate "Probabilistic medical segmentation"
module imageViewerHelper
using Documenter
using ColorTypes
using Colors, ColorSchemeTools
using Makie
export calculateMouseAndSetmask
export createMedicalImageColorSchemeB
# using AbstractPlotting
```#doc
given mouse event modifies mask accordingly
maskArr - the 3 dimensional bit array that has exactly the same dimensions as main Array storing image
event - mouse event passed from Makie
sc - scene we are using in Makie
```
function calculateMouseAndSetmask(maskArr, event,sc,dims,sliceNumb)
#position from top left corner
xMouse= Makie.to_world(sc,event.data)[1]
yMouse= Makie.to_world(sc,event.data)[2]
#data about height and width in layout
compBoxWidth = 510
compBoxHeight = 510
#image dimensions - number of pixels from medical image for example ct scan
pixelsNumbInX =dims[1]
pixelsNumbInY =dims[2]
#calculating over which image pixel we are
calculatedXpixel =convert(Int32, round( (xMouse/compBoxWidth)*pixelsNumbInX) )
calculatedYpixel = convert(Int32,round( (yMouse/compBoxHeight)*pixelsNumbInY ))
sliceNumbConv =convert(Int32,round( sliceNumb[] ))
#appropriately modyfing wanted pixels in mask array
return markMaskArrayPatch( maskArr ,CartesianIndex(calculatedXpixel, calculatedYpixel, sliceNumbConv ),2)
end
```#doc
maskArr - the 3 dimensional bit array that has exactly the same dimensions as main Array storing image
point - cartesian coordinates of point around which we want to modify the 3 dimensional array from 0 to 1
```
function markMaskArrayPatch(maskArr, pointCart::CartesianIndex{3}, patchSize ::Int64)
ones = CartesianIndex(patchSize,patchSize,patchSize) # cartesian 3 dimensional index used for calculations to get range of the cartesian indicis to analyze
maskArrB = maskArr[]
for J in (pointCart-ones):(pointCart+ones)
diff = J - pointCart # diffrence between dimensions relative to point of origin
if cartesianTolinear(diff) <= patchSize
maskArrB[J]=1
end
end
return maskArrB
end
```#doc
works only for 3d cartesian coordinates
cart - cartesian coordinates of point where we will add the dimensions ...
```
function cartesianTolinear(pointCart::CartesianIndex{3}) :: Int16
abs(pointCart[1])+ abs(pointCart[2])+abs(pointCart[3])
end
```#doc
creating grey scheme colors for proper display of medical image mainly CT scan
min_shown_white - max_shown_black range over which the gradint of greys will be shown
truemax - truemin the range of values in the image for which we are creating the scale
```
#taken from https://stackoverflow.com/questions/67727977/how-to-create-julia-color-scheme-for-displaying-ct-scan-makie-jl/67756158#67756158
function createMedicalImageColorSchemeB(min_shown_white,max_shown_black,truemax,truemin ) ::Vector{Any}
# println("max_shown_black - truemin + 1")
# println(max_shown_black - truemin + 1)
# println(" min_shown_white - max_shown_black - 1")
# println( min_shown_white - max_shown_black - 1)
# println("truemax - min_shown_white + 1")
# println(truemax - min_shown_white + 1)
return [fill(colorant"black", max_shown_black - truemin + 1);
collect(make_colorscheme(identity, identity, identity,
length = min_shown_white - max_shown_black - 1));
fill(colorant"white", truemax - min_shown_white + 1)]
end
end #module