shaderlib: Implement place_texture() and provide an example, replace mix.gdshader example; implements #17

examples/CREDITS.md

@@ -1,5 +1,5 @@
 
 # Example Images
 
-- swamp.jpg by [clfr21](https://pixabay.com/de/users/clfr21-6530007/)
-- overlay.jpg by [Humusak](https://pixabay.com/de/users/humusak-137455/)
+- swamp.jpg by [clfr21 on Pixabay](https://pixabay.com/de/users/clfr21-6530007/)
+- grass.png by [GDJ on Pixabay](https://pixabay.com/users/gdj-1086657/)

examples/grass.png.import

@@ -2,16 +2,16 @@
 
 importer="texture"
 type="CompressedTexture2D"
-uid="uid://8101nnc8cx4o"
-path="res://.godot/imported/overlay.jpg-b6d13e0def59877969c9eda02fa4244e.ctex"
+uid="uid://c1mh1d2f3u4ju"
+path="res://.godot/imported/grass.png-30af7213ed2d70b810b4ae788314a9e9.ctex"
 metadata={
 "vram_texture": false
 }
 
 [deps]
 
-source_file="res://examples/overlay.jpg"
-dest_files=["res://.godot/imported/overlay.jpg-b6d13e0def59877969c9eda02fa4244e.ctex"]
+source_file="res://examples/grass.png"
+dest_files=["res://.godot/imported/grass.png-30af7213ed2d70b810b4ae788314a9e9.ctex"]
 
 [params]
 

examples/mix.gdshader

@@ -1,10 +0,0 @@
-shader_type canvas_item;
-
-//!load ./swamp.jpg
-
-//!load+ img2 ./overlay.jpg
-uniform sampler2D img2: repeat_enable, filter_nearest;
-
-void fragment() {
-	COLOR = mix(COLOR, texture(img2, UV), .2);
-}

examples/place_texture.gdshader

@@ -0,0 +1,14 @@
+shader_type canvas_item;
+
+#include "res://shaderlib/transform.gdshaderinc"
+
+//!load ./swamp.jpg
+//!load+ img2 ./grass.png
+
+uniform sampler2D img2: repeat_disable, filter_nearest;
+
+void fragment() {
+	vec4 grass = place_texture(img2, UV, TEXTURE_PIXEL_SIZE, vec2(0, .47), vec2(1));
+	grass.rgb += (vec3(0.03, 0.07, 0.11) - ((UV.y - .8) * 0.15)); // color correction
+	COLOR.rgb = mix(COLOR.rgb, grass.rgb, grass.a);
+}