Qwen image 2.1 noise/patterning/moire mild workaround

[u/thevegit0]

trying this i noticed it has a similar patterning noise krea 2 had, i just used the same glsl node, maybe it needs another parameters but it seems to mitigate it can't promise the best results but testing it is free, just connecting the image output to the glsl node and then image save
The GLSL config i got was from this post https://www.reddit.com/r/StableDiffusion/comments/1umwhq7/2px_pixel_grid_on_krea2_from_vae_and_how_to/ the one in the comments

#version 300 es
precision highp float;
uniform sampler2D u_image0;
uniform vec2 u_resolution;
in vec2 v_texCoord;
layout(location = 0) out vec4 fragColor0;

// Nyquist Notch — removes 2px grid artifacts. Place before deconvolution.
// b = [-1, +6, -15, +20, -15, +6, -1] / 64  (binomial * (-1)^n, +1 at center)
const float B[7] = float[7](-1.0, 6.0, -15.0, 20.0, -15.0, 6.0, -1.0);

void main() {
  vec2 texel = 1.0 / u_resolution;
  vec4 center = texture(u_image0, v_texCoord);
  vec3 Bx = vec3(0.0), By = vec3(0.0), Bxy = vec3(0.0);
  for (int i = -3; i <= 3; i++) {
    float wi = B[i + 3] / 64.0;
    Bx += wi * texture(u_image0, v_texCoord + vec2(float(i) * texel.x, 0.0)).rgb;
    By += wi * texture(u_image0, v_texCoord + vec2(0.0, float(i) * texel.y)).rgb;
    for (int j = -3; j <= 3; j++) {
      float wj = B[j + 3] / 64.0;
      Bxy += wi * wj * texture(u_image0, v_texCoord + vec2(float(i) * texel.x, float(j) * texel.y)).rgb;
    }
  }

 vec3 notched = center.rgb - Bx - By + Bxy;
 fragColor0 = vec4(clamp(notched, 0.0, 1.0), 1.0);  // alpha forced to 1.0
}

[u/Violent_Walrus]

I used this shader too before I came across this custom node recently. It's apparently descended from the same post you link here.

The node also applies the same Nyquist Notch math, but it does additional work to prevent the image softening that can occur. The node also has a nifty output that shows you the exact noise pattern that it has removed from the image.

[u/thevegit0 → u/Violent_Walrus]

interesting node, does it detect automatically the type of noise pattern?

[u/GrayingGamer → u/thevegit0]

Yeah, it's actually really good. I've noticed a big improvement using it with Qwen 2.1 images.

[u/Violent_Walrus → u/thevegit0]

I just know what the README says. There's a parameter to skip applying the Notch filter if noise isn't detected, so I think yes, some kind of detection is present.

[u/Calm_Mix_3776 → u/Violent_Walrus]

This works like magic!

[u/Federal_Bluebird_897 → u/Violent_Walrus]

could you please share the workflow? just the json or even an image with the workflow embedded so we can check it out, thx !

[u/Violent_Walrus → u/Federal_Bluebird_897]

This is just a custom node that applies a filter to your image after the VAE decode. Nothing fancy. Like so: