Fix Chroma attention padding order and update docs to use `lodestones/Chroma1-HD` (#12508)

* [Fix] Move attention mask padding after T5 embedding

* [Fix] Move attention mask padding after T5 embedding

* Clean up whitespace in pipeline_chroma.py

Removed unnecessary blank lines for cleaner code.

* Fix

* Fix

* Update model to final Chroma1-HD checkpoint

* Update to Chroma1-HD

* Update model to Chroma1-HD

* Update model to Chroma1-HD

* Update Chroma model links to Chroma1-HD

* Add comment about padding/masking

* Fix checkpoint/repo references

* Apply style fixes

---------
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

docs/source/en/api/models/chroma_transformer.md

@@ -12,7 +12,7 @@ specific language governing permissions and limitations under the License.
 
 # ChromaTransformer2DModel
 
-A modified flux Transformer model from [Chroma](https://huggingface.co/lodestones/Chroma)
+A modified flux Transformer model from [Chroma](https://huggingface.co/lodestones/Chroma1-HD)
 
 ## ChromaTransformer2DModel
 

docs/source/en/api/pipelines/chroma.md

@@ -19,20 +19,21 @@ specific language governing permissions and limitations under the License.
 
 Chroma is a text to image generation model based on Flux.
 
-Original model checkpoints for Chroma can be found [here](https://huggingface.co/lodestones/Chroma).
+Original model checkpoints for Chroma can be found here:
+* High-resolution finetune: [lodestones/Chroma1-HD](https://huggingface.co/lodestones/Chroma1-HD)
+* Base model: [lodestones/Chroma1-Base](https://huggingface.co/lodestones/Chroma1-Base)
+* Original repo with progress checkpoints: [lodestones/Chroma](https://huggingface.co/lodestones/Chroma) (loading this repo with `from_pretrained` will load a Diffusers-compatible version of the `unlocked-v37` checkpoint)
 
 > [!TIP]
 > Chroma can use all the same optimizations as Flux.
 
 ## Inference
 
-The Diffusers version of Chroma is based on the [`unlocked-v37`](https://huggingface.co/lodestones/Chroma/blob/main/chroma-unlocked-v37.safetensors) version of the original model, which is available in the [Chroma repository](https://huggingface.co/lodestones/Chroma).
-
 ```python
 import torch
 from diffusers import ChromaPipeline
 
-pipe = ChromaPipeline.from_pretrained("lodestones/Chroma", torch_dtype=torch.bfloat16)
+pipe = ChromaPipeline.from_pretrained("lodestones/Chroma1-HD", torch_dtype=torch.bfloat16)
 pipe.enable_model_cpu_offload()
 
 prompt = [
@@ -63,10 +64,10 @@ Then run the following example
 import torch
 from diffusers import ChromaTransformer2DModel, ChromaPipeline
 
-model_id = "lodestones/Chroma"
+model_id = "lodestones/Chroma1-HD"
 dtype = torch.bfloat16
 
-transformer = ChromaTransformer2DModel.from_single_file("https://huggingface.co/lodestones/Chroma/blob/main/chroma-unlocked-v37.safetensors", torch_dtype=dtype)
+transformer = ChromaTransformer2DModel.from_single_file("https://huggingface.co/lodestones/Chroma1-HD/blob/main/Chroma1-HD.safetensors", torch_dtype=dtype)
 
 pipe = ChromaPipeline.from_pretrained(model_id, transformer=transformer, torch_dtype=dtype)
 pipe.enable_model_cpu_offload()

src/diffusers/models/transformers/transformer_chroma.py

@@ -379,7 +379,7 @@ class ChromaTransformer2DModel(
     """
     The Transformer model introduced in Flux, modified for Chroma.
 
-    Reference: https://huggingface.co/lodestones/Chroma
+    Reference: https://huggingface.co/lodestones/Chroma1-HD
 
     Args:
         patch_size (`int`, defaults to `1`):

src/diffusers/pipelines/chroma/pipeline_chroma.py

@@ -53,8 +53,8 @@ EXAMPLE_DOC_STRING = """
         >>> import torch
         >>> from diffusers import ChromaPipeline
 
-        >>> model_id = "lodestones/Chroma"
-        >>> ckpt_path = "https://huggingface.co/lodestones/Chroma/blob/main/chroma-unlocked-v37.safetensors"
+        >>> model_id = "lodestones/Chroma1-HD"
+        >>> ckpt_path = "https://huggingface.co/lodestones/Chroma1-HD/blob/main/Chroma1-HD.safetensors"
         >>> transformer = ChromaTransformer2DModel.from_single_file(ckpt_path, torch_dtype=torch.bfloat16)
         >>> pipe = ChromaPipeline.from_pretrained(
         ...     model_id,
@@ -158,7 +158,7 @@ class ChromaPipeline(
     r"""
     The Chroma pipeline for text-to-image generation.
 
-    Reference: https://huggingface.co/lodestones/Chroma/
+    Reference: https://huggingface.co/lodestones/Chroma1-HD/
 
     Args:
         transformer ([`ChromaTransformer2DModel`]):
@@ -233,20 +233,23 @@ class ChromaPipeline(
             return_tensors="pt",
         )
         text_input_ids = text_inputs.input_ids
-        attention_mask = text_inputs.attention_mask.clone()
+        tokenizer_mask = text_inputs.attention_mask
 
-        # Chroma requires the attention mask to include one padding token
-        seq_lengths = attention_mask.sum(dim=1)
-        mask_indices = torch.arange(attention_mask.size(1)).unsqueeze(0).expand(batch_size, -1)
-        attention_mask = (mask_indices <= seq_lengths.unsqueeze(1)).bool()
+        tokenizer_mask_device = tokenizer_mask.to(device)
 
+        # unlike FLUX, Chroma uses the attention mask when generating the T5 embedding
         prompt_embeds = self.text_encoder(
-            text_input_ids.to(device), output_hidden_states=False, attention_mask=attention_mask.to(device)
+            text_input_ids.to(device),
+            output_hidden_states=False,
+            attention_mask=tokenizer_mask_device,
         )[0]
 
-        dtype = self.text_encoder.dtype
         prompt_embeds = prompt_embeds.to(dtype=dtype, device=device)
-        attention_mask = attention_mask.to(device=device)
+
+        # for the text tokens, chroma requires that all except the first padding token are masked out during the forward pass through the transformer
+        seq_lengths = tokenizer_mask_device.sum(dim=1)
+        mask_indices = torch.arange(tokenizer_mask_device.size(1), device=device).unsqueeze(0).expand(batch_size, -1)
+        attention_mask = (mask_indices <= seq_lengths.unsqueeze(1)).to(dtype=dtype, device=device)
 
         _, seq_len, _ = prompt_embeds.shape
 

src/diffusers/pipelines/chroma/pipeline_chroma_img2img.py

@@ -53,8 +53,8 @@ EXAMPLE_DOC_STRING = """
         >>> import torch
         >>> from diffusers import ChromaTransformer2DModel, ChromaImg2ImgPipeline
 
-        >>> model_id = "lodestones/Chroma"
-        >>> ckpt_path = "https://huggingface.co/lodestones/Chroma/blob/main/chroma-unlocked-v37.safetensors"
+        >>> model_id = "lodestones/Chroma1-HD"
+        >>> ckpt_path = "https://huggingface.co/lodestones/Chroma1-HD/blob/main/Chroma1-HD.safetensors"
         >>> pipe = ChromaImg2ImgPipeline.from_pretrained(
         ...     model_id,
         ...     transformer=transformer,
@@ -170,7 +170,7 @@ class ChromaImg2ImgPipeline(
     r"""
     The Chroma pipeline for image-to-image generation.
 
-    Reference: https://huggingface.co/lodestones/Chroma/
+    Reference: https://huggingface.co/lodestones/Chroma1-HD/
 
     Args:
         transformer ([`ChromaTransformer2DModel`]):
@@ -247,20 +247,21 @@ class ChromaImg2ImgPipeline(
             return_tensors="pt",
         )
         text_input_ids = text_inputs.input_ids
-        attention_mask = text_inputs.attention_mask.clone()
+        tokenizer_mask = text_inputs.attention_mask
 
-        # Chroma requires the attention mask to include one padding token
-        seq_lengths = attention_mask.sum(dim=1)
-        mask_indices = torch.arange(attention_mask.size(1)).unsqueeze(0).expand(batch_size, -1)
-        attention_mask = (mask_indices <= seq_lengths.unsqueeze(1)).long()
+        tokenizer_mask_device = tokenizer_mask.to(device)
 
         prompt_embeds = self.text_encoder(
-            text_input_ids.to(device), output_hidden_states=False, attention_mask=attention_mask.to(device)
+            text_input_ids.to(device),
+            output_hidden_states=False,
+            attention_mask=tokenizer_mask_device,
         )[0]
 
-        dtype = self.text_encoder.dtype
         prompt_embeds = prompt_embeds.to(dtype=dtype, device=device)
-        attention_mask = attention_mask.to(dtype=dtype, device=device)
+
+        seq_lengths = tokenizer_mask_device.sum(dim=1)
+        mask_indices = torch.arange(tokenizer_mask_device.size(1), device=device).unsqueeze(0).expand(batch_size, -1)
+        attention_mask = (mask_indices <= seq_lengths.unsqueeze(1)).to(dtype=dtype, device=device)
 
         _, seq_len, _ = prompt_embeds.shape