Correct the description of image compression

README.md

@@ -101,7 +101,7 @@ This repository currently hosts the **pixel-level annotated subset** of X-AIGD,
 
 ### Data Fields
 
-- `image`: The AI-generated image (PNG or JPEG format).
+- `image`: The AI-generated image (raw images with **PNG** format).
 - `generator`: Name of the text-to-image generator.
 - `uid`: Unique identifier for the image.
 - `labels`: List of human-annotated artifacts, each containing:
@@ -110,7 +110,7 @@ This repository currently hosts the **pixel-level annotated subset** of X-AIGD,
 - `original_prompt`, `positive_prompt`, `negative_prompt`: Text prompts used for generation.
 - `num_inference_steps`, `guidance_scale`, `seed`, `scheduler`: Generation parameters.
 - `width`, `height`: Image resolution.
-- `image_format`, `jpeg_quality`, `chroma_subsampling`: Image compression details.
+- `image_format`, `jpeg_quality`, `chroma_subsampling`: Image compression details of the _corresponding real image_ (used for optional compression alignment).
 
 ### UID Correspondence