bring histogram matching example back (#226)

Author: johnnychen94

Project.toml

@@ -29,6 +29,7 @@ MosaicViews = "e94cdb99-869f-56ef-bcf0-1ae2bcbe0389"
 Noise = "81d43f40-5267-43b7-ae1c-8b967f377efa"
 OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
 PaddedViews = "5432bcbf-9aad-5242-b902-cca2824c8663"
+Plots = "91a5bcdd-55d7-5caf-9e0b-520d859cae80"
 Rotations = "6038ab10-8711-5258-84ad-4b1120ba62dc"
 SimpleTraits = "699a6c99-e7fa-54fc-8d76-47d257e15c1d"
 TestImages = "5e47fb64-e119-507b-a336-dd2b206d9990"
@@ -65,6 +66,7 @@ MosaicViews = "0"
 Noise = "0.2"
 OffsetArrays = "1.0"
 PaddedViews = "0"
+Plots = "1.21"
 Rotations = "1"
 SimpleTraits = "0"
 TestImages = "0, 1.0"

docs/examples/spatial_transformation/histogram_matching.jl.bak renamed to docs/examples/spatial_transformation/histogram_matching.jl

@@ -2,6 +2,11 @@ using Documenter, DemoCards
 using Images, ImageFiltering, ImageSegmentation, ImageFeatures, PaddedViews
 using ImageContrastAdjustment, TestImages, FileIO, MosaicViews, ImageMorphology
 
+# loading Plots before generating demos (might be helpful to avoid segfaults)
+using Plots
+ENV["GKSwstype"] = "nul" # needed for the GR backend on headless servers
+gr()
+
 branch = "master"
 
 demos, demos_cb, demo_assets = makedemos("examples"; branch = branch)