Add nodes to demo hardlight being used to raise constrast with an s-curve

Introduces the same fantasy image in https://www.lightxapp.com/curves-tool-in-photo-editing/ which explains what an s-curve is

overlay_and_hardlight.lua

@@ -25,6 +25,25 @@ minetest.register_node("texturemodifiertest:HardlightBlend_Gradient_with_Testima
 	groups = {cracky = 1, oddly_breakable_by_hand = 1},
 })
 
+minetest.register_node("texturemodifiertest:Hardlight_to_raise_contrast", {
+	description = "Hard light blending an image with itself applys an s-curve effect that increases contrast without clipping",
+	tiles = {"testimage.png^[hardlight:testimage.png"},
+	groups = {cracky = 1, oddly_breakable_by_hand = 1},
+})
+
+minetest.register_node("texturemodifiertest:Fantasy_testimage", {
+	description = "Fantasy test image unmodified",
+	tiles = {"fantasy.png"},
+	groups = {cracky = 1, oddly_breakable_by_hand = 1},
+})
+
+minetest.register_node("texturemodifiertest:Hardlight_to_raise_contrast_fantasy", {
+	description = "Hard light blending an image with itself applys an s-curve effect that increases contrast without clipping",
+	tiles = {"fantasy.png^[hardlight:fantasy.png"},
+	groups = {cracky = 1, oddly_breakable_by_hand = 1},
+})
+
+
 -- Mismatched texture dimensions (Texture scaling)
 minetest.register_node("texturemodifiertest:OverlayBlend_Testimage_with_TestImage2", {
 	description = "Overlay blend of Test image with TestTVScreen",