Fix #13094: fix: correct Z-Image guidance scale threshold from > 1 to > 0

src/diffusers/pipelines/z_image/pipeline_z_image.py

@@ -339,10 +339,9 @@ def __call__(
                 will be used.
             guidance_scale (`float`, *optional*, defaults to 5.0):
                 Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale >
-                1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`,
-                usually at the expense of lower image quality.
+                Z-Image uses the formula `pred = pos + guidance_scale * (pos - neg)`, so guidance scale is enabled
+                by setting `guidance_scale > 0`. Higher guidance scale encourages to generate images that are closely
+                linked to the text `prompt`, usually at the expense of lower image quality.
             cfg_normalization (`bool`, *optional*, defaults to False):
                 Whether to apply configuration normalization.
             cfg_truncation (`float`, *optional*, defaults to 1.0):

src/diffusers/pipelines/z_image/pipeline_z_image_controlnet.py

@@ -431,10 +431,9 @@ def __call__(
                 will be used.
             guidance_scale (`float`, *optional*, defaults to 5.0):
                 Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale >
-                1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`,
-                usually at the expense of lower image quality.
+                Z-Image uses the formula `pred = pos + guidance_scale * (pos - neg)`, so guidance scale is enabled
+                by setting `guidance_scale > 0`. Higher guidance scale encourages to generate images that are closely
+                linked to the text `prompt`, usually at the expense of lower image quality.
             control_image (`PipelineImageInput`):
                 The ControlNet input condition to provide guidance to the `transformer` for generation. If the type is
                 specified as `torch.Tensor`, it is passed to ControlNet as is. `PIL.Image.Image` can also be accepted

src/diffusers/pipelines/z_image/pipeline_z_image_controlnet_inpaint.py

@@ -440,10 +440,9 @@ def __call__(
                 will be used.
             guidance_scale (`float`, *optional*, defaults to 5.0):
                 Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale >
-                1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`,
-                usually at the expense of lower image quality.
+                Z-Image uses the formula `pred = pos + guidance_scale * (pos - neg)`, so guidance scale is enabled
+                by setting `guidance_scale > 0`. Higher guidance scale encourages to generate images that are closely
+                linked to the text `prompt`, usually at the expense of lower image quality.
             image (`PipelineImageInput`):
                 `Image`, numpy array or tensor representing an image batch to be inpainted (which parts of the image to
                 be masked out with `mask_image` and repainted according to `prompt`).

src/diffusers/pipelines/z_image/pipeline_z_image_img2img.py

@@ -424,10 +424,9 @@ def __call__(
                 will be used.
             guidance_scale (`float`, *optional*, defaults to 5.0):
                 Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale >
-                1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`,
-                usually at the expense of lower image quality.
+                Z-Image uses the formula `pred = pos + guidance_scale * (pos - neg)`, so guidance scale is enabled
+                by setting `guidance_scale > 0`. Higher guidance scale encourages to generate images that are closely
+                linked to the text `prompt`, usually at the expense of lower image quality.
             cfg_normalization (`bool`, *optional*, defaults to False):
                 Whether to apply configuration normalization.
             cfg_truncation (`float`, *optional*, defaults to 1.0):

src/diffusers/pipelines/z_image/pipeline_z_image_inpaint.py

@@ -597,10 +597,9 @@ def __call__(
                 will be used.
             guidance_scale (`float`, *optional*, defaults to 5.0):
                 Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale >
-                1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`,
-                usually at the expense of lower image quality.
+                Z-Image uses the formula `pred = pos + guidance_scale * (pos - neg)`, so guidance scale is enabled
+                by setting `guidance_scale > 0`. Higher guidance scale encourages to generate images that are closely
+                linked to the text `prompt`, usually at the expense of lower image quality.
             cfg_normalization (`bool`, *optional*, defaults to False):
                 Whether to apply configuration normalization.
             cfg_truncation (`float`, *optional*, defaults to 1.0):

src/diffusers/pipelines/z_image/pipeline_z_image_omni.py

@@ -410,10 +410,9 @@ def __call__(
                 will be used.
             guidance_scale (`float`, *optional*, defaults to 5.0):
                 Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale >
-                1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`,
-                usually at the expense of lower image quality.
+                Z-Image uses the formula `pred = pos + guidance_scale * (pos - neg)`, so guidance scale is enabled
+                by setting `guidance_scale > 0`. Higher guidance scale encourages to generate images that are closely
+                linked to the text `prompt`, usually at the expense of lower image quality.
             cfg_normalization (`bool`, *optional*, defaults to False):
                 Whether to apply configuration normalization.
             cfg_truncation (`float`, *optional*, defaults to 1.0):