// AdvancedMosaic — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/AdvancedMosaic.glsl
// Author: Sergey Kosarevsky
// License: MIT
// Description: Both images break into large blocks that blend, then sharpen into the incoming image

uniform shader _from;
uniform shader _to;
uniform float2 _resolution;
uniform float progress;
uniform float ratio;

vec4 getFromColor(vec2 uv) { return vec4(unpremul(_from.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }
vec4 getToColor(vec2 uv) { return vec4(unpremul(_to.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }

uniform float pixelSize; 

vec4 transition(vec2 uv) {
  float T = progress;
  float half_ = 0.5;
  float size = (T < half_) ? mix(1.0, pixelSize, T / half_) : mix(pixelSize, 1.0, (T - half_) / half_);
  float D = size * 0.005;
  
  vec2 UV = (uv - 0.5) / D;
  vec2 coord = clamp(D * (ceil(UV - 0.5)) + 0.5, 0.0, 1.0);
  vec4 C0 = getFromColor(coord);
  vec4 C1 = getToColor(coord);
  return mix(C0, C1, T);
}

half4 main(float2 _coord) {
  vec2 _uv = _coord / _resolution;
  vec4 _c = clamp(transition(vec2(_uv.x, 1.0 - _uv.y)), 0.0, 1.0);
  return half4(_c.rgb * _c.a, _c.a);
}