2D outline stroke

Adds an outer outline stroke to a Sprite texture. Alpha acts as the defining border which the stroke follows. This shader comes from GD Quest’s library of free shaders.

Shader code

shader_type canvas_item;

uniform vec4 line_color : hint_color = vec4(1);
uniform float line_thickness : hint_range(0, 10) = 1.0;

void fragment() {
	vec2 size = TEXTURE_PIXEL_SIZE * line_thickness;
	
	float outline = texture(TEXTURE, UV + vec2(-size.x, 0)).a;
	outline += texture(TEXTURE, UV + vec2(0, size.y)).a;
	outline += texture(TEXTURE, UV + vec2(size.x, 0)).a;
	outline += texture(TEXTURE, UV + vec2(0, -size.y)).a;
	outline += texture(TEXTURE, UV + vec2(-size.x, size.y)).a;
	outline += texture(TEXTURE, UV + vec2(size.x, size.y)).a;
	outline += texture(TEXTURE, UV + vec2(-size.x, -size.y)).a;
	outline += texture(TEXTURE, UV + vec2(size.x, -size.y)).a;
	outline = min(outline, 1.0);
	
	vec4 color = texture(TEXTURE, UV);
	COLOR = mix(color, line_color, outline - color.a);
}

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