// pixelize — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/pixelize.glsl
// Author: gre
// License: MIT
// Description: Both images pixelate, crossfade, then sharpen again

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 ivec2 squaresMin; 

uniform int steps; 

vec4 transition(vec2 uv) {
  float d = min(progress, 1.0 - progress);
  float dist = steps>0 ? ceil(d * float(steps)) / float(steps) : d;
  vec2 squareSize = 2.0 * dist / vec2(squaresMin);
  vec2 p = dist>0.0 ? (floor(uv / squareSize) + 0.5) * squareSize : uv;
  return mix(getFromColor(p), getToColor(p), progress);
}

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);
}