// 5×5 variant for 7→4 channels (vec4-optimized)
// Assumes 'tex' is already normalized to [-1,1]
// UV coordinates remain in [0,1] and are normalized internally
// weights: array<vec4<f32>, 200> (25 pos × 4 ch × 2 vec4)
fn cnn_conv5x5_7to4(
  tex: texture_2d<f32>,
  samp: sampler,
  uv: vec2<f32>,
  resolution: vec2<f32>,
  gray: f32,
  weights: array<vec4<f32>, 200>
) -> vec4<f32> {
  let step = 1.0 / resolution;
  let uv_norm = (uv - 0.5) * 2.0;

  var sum = vec4<f32>(0.0);
  var pos = 0;

  for (var dy = -2; dy <= 2; dy++) {
    for (var dx = -2; dx <= 2; dx++) {
      let offset = vec2<f32>(f32(dx), f32(dy)) * step;
      let rgbd = textureSample(tex, samp, uv + offset);
      let in1 = vec4<f32>(uv_norm, gray, 1.0);

      sum.r += dot(weights[pos+0], rgbd) + dot(weights[pos+1], in1);
      sum.g += dot(weights[pos+2], rgbd) + dot(weights[pos+3], in1);
      sum.b += dot(weights[pos+4], rgbd) + dot(weights[pos+5], in1);
      sum.a += dot(weights[pos+6], rgbd) + dot(weights[pos+7], in1);
      pos += 8;
    }
  }

  return sum;
}

// 5×5 variant for 7→1 channel (vec4-optimized)
// Assumes 'tex' is already normalized to [-1,1]
// UV coordinates remain in [0,1] and are normalized internally
// weights: array<vec4<f32>, 50> (25 pos × 2 vec4)
fn cnn_conv5x5_7to1(
  tex: texture_2d<f32>,
  samp: sampler,
  uv: vec2<f32>,
  resolution: vec2<f32>,
  gray: f32,
  weights: array<vec4<f32>, 50>
) -> f32 {
  let step = 1.0 / resolution;
  let uv_norm = (uv - 0.5) * 2.0;

  var sum = 0.0;
  var pos = 0;

  for (var dy = -2; dy <= 2; dy++) {
    for (var dx = -2; dx <= 2; dx++) {
      let offset = vec2<f32>(f32(dx), f32(dy)) * step;
      let rgbd = textureSample(tex, samp, uv + offset);
      let in1 = vec4<f32>(uv_norm, gray, 1.0);

      sum += dot(weights[pos], rgbd) + dot(weights[pos+1], in1);
      pos += 2;
    }
  }

  return clamp(sum, 0.0, 1.0);
}

// Source layer: 7→4 channels (vec4-optimized)
// Normalizes [0,1] input to [-1,1] internally
fn cnn_conv5x5_7to4_src(
  tex: texture_2d<f32>,
  samp: sampler,
  uv: vec2<f32>,
  resolution: vec2<f32>,
  weights: array<vec4<f32>, 200>
) -> vec4<f32> {
  let step = 1.0 / resolution;

  let original = (textureSample(tex, samp, uv) - 0.5) * 2.0;
  let gray = dot(original.rgb, vec3<f32>(0.2126, 0.7152, 0.0722));
  let uv_norm = (uv - 0.5) * 2.0;

  var sum = vec4<f32>(0.0);
  var pos = 0;

  for (var dy = -2; dy <= 2; dy++) {
    for (var dx = -2; dx <= 2; dx++) {
      let offset = vec2<f32>(f32(dx), f32(dy)) * step;
      let rgbd = (textureSample(tex, samp, uv + offset) - 0.5) * 2.0;
      let in1 = vec4<f32>(uv_norm, gray, 1.0);

      sum.r += dot(weights[pos+0], rgbd) + dot(weights[pos+1], in1);
      sum.g += dot(weights[pos+2], rgbd) + dot(weights[pos+3], in1);
      sum.b += dot(weights[pos+4], rgbd) + dot(weights[pos+5], in1);
      sum.a += dot(weights[pos+6], rgbd) + dot(weights[pos+7], in1);
      pos += 8;
    }
  }

  return sum;
}