slang-shaders/retro/shaders/ascii.slang

#version 450

// Bitmap to ASCII (not really) fragment shader by movAX13h, September 2013
// --- This shader is now used in Pixi JS ---
// Pixi JS is MIT-licensed

layout(push_constant) uniform Push
{
	vec4 SourceSize;
	vec4 OriginalSize;
	vec4 OutputSize;
	uint FrameCount;
} params;

layout(std140, set = 0, binding = 0) uniform UBO
{
	mat4 MVP;
} global;

float character(float n, vec2 p) // some compilers have the word "char" reserved
{
	p = floor(p*vec2(4.0, -4.0) + 2.5);
	if (clamp(p.x, 0.0, 4.0) == p.x && clamp(p.y, 0.0, 4.0) == p.y)
	{
		if (int(mod(n/exp2(p.x + 5.0*p.y), 2.0)) == 1) return 1.0;
	}	
	return 0.0;
}

#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;

void main()
{
   gl_Position = global.MVP * Position;
   vTexCoord = TexCoord;
}

#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;

void main()
{
	vec2 uv = vTexCoord * params.OutputSize.xy;
	vec3 col = texture(Source, floor(uv/8.0)*8.0/params.OutputSize.xy).rgb;	
	
	float gray = dot(col.rgb, vec3(0.299, 0.587, 0.114));
	
	float n =  65536.0;             // .
	if (gray > 0.2) n = 65600.0;    // :
	if (gray > 0.3) n = 332772.0;   // *
	if (gray > 0.4) n = 15255086.0; // o 
	if (gray > 0.5) n = 23385164.0; // &
	if (gray > 0.6) n = 15252014.0; // 8
	if (gray > 0.7) n = 13199452.0; // @
	if (gray > 0.8) n = 11512810.0; // #
	
	vec2 p = mod(uv/4.0, 2.0) - vec2(1.0);
	col = col*character(n, p);
	
   FragColor = vec4(col, 1.0);
}