Add example shaders_shapes_outline.c (#1883)

examples/shaders/resources/LICENSE.md

@@ -9,3 +9,5 @@
 | raysan.png         | [@raysan5](https://github.com/raysan5)      | [CC0](https://creativecommons.org/publicdomain/zero/1.0/)   | - |
 | space.png          | ❔             | ❔       | - |
 | texel_checker.png  | [@raysan5](https://github.com/raysan5)      | [CC0](https://creativecommons.org/publicdomain/zero/1.0/)   | Made with [UV Checker Map Maker](http://uvchecker.byvalle.com/) |
+| egg.png            | [@GoldenThumbs](https://github.com/GoldenThumbs) |
+| torus.png          | [@GoldenThumbs](https://github.com/GoldenThumbs) |

examples/shaders/resources/shaders/glsl100/outline.fs

@@ -0,0 +1,35 @@
+#version 100
+
+precision mediump float;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+uniform vec2 texScale;
+
+// Function for drawing outlines on alpha-blended textures
+vec4 DrawOutline(sampler2D tex, vec2 uv, vec2 lineScale, vec3 lineCol)
+{
+	vec2 texelScale = 1.0 / lineScale;
+	vec4 center = texture2D(tex, uv); // We sample the center texel, (with all color data)
+	// Next we sample four corner texels, but only for the alpha channel (this is for the outline)
+	vec4 corners;
+	corners.x = texture2D(tex, uv+vec2( texelScale.x, texelScale.y)).a;
+	corners.y = texture2D(tex, uv+vec2( texelScale.x,-texelScale.y)).a;
+	corners.z = texture2D(tex, uv+vec2(-texelScale.x, texelScale.y)).a;
+	corners.w = texture2D(tex, uv+vec2(-texelScale.x,-texelScale.y)).a;
+	
+	float outline = min(dot(corners, vec4(1.0)), 1.0);
+	vec4 col = mix(vec4(0.0), vec4(lineCol, 1.0), outline);
+	col = mix(col, center, center.a);
+	return col;
+}
+
+void main()
+{
+	gl_FragColor = DrawOutline(texture0, fragTexCoord, texScale, vec3(0.0));
+}

examples/shaders/resources/shaders/glsl330/outline.fs

@@ -0,0 +1,36 @@
+#version 330
+
+// Input vertex attributes (from vertex shader)
+in vec2 fragTexCoord;
+in vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+uniform vec2 texScale;
+
+// Output fragment color
+out vec4 finalColor;
+
+// Function for drawing outlines on alpha-blended textures
+vec4 DrawOutline(sampler2D tex, vec2 uv, vec2 lineScale, vec3 lineCol)
+{
+	vec2 texelScale = 1.0 / lineScale;
+	vec4 center = texture(tex, uv); // We sample the center texel, (with all color data)
+	// Next we sample four corner texels, but only for the alpha channel (this is for the outline)
+	vec4 corners;
+	corners.x = texture(tex, uv+vec2( texelScale.x, texelScale.y)).a;
+	corners.y = texture(tex, uv+vec2( texelScale.x,-texelScale.y)).a;
+	corners.z = texture(tex, uv+vec2(-texelScale.x, texelScale.y)).a;
+	corners.w = texture(tex, uv+vec2(-texelScale.x,-texelScale.y)).a;
+	
+	float outline = min(dot(corners, vec4(1.0)), 1.0);
+	vec4 col = mix(vec4(0.0), vec4(lineCol, 1.0), outline);
+	col = mix(col, center, center.a);
+	return col;
+}
+
+void main()
+{
+	finalColor = DrawOutline(texture0, fragTexCoord, texScale, vec3(0.0));
+}