🎈LG_FastPreview

Preview nodes are the most underrated part of ComfyUI - the difference between watching your workflow work and trusting it works. LG_FastPreview is a small one with a genuinely useful knob: it saves to ComfyUI's temp directory (not your output folder, which is the whole point) and lets you pick the format - PNG, JPEG, or WEBP - plus a quality setting. Its description calls itself "快速预览图像" (quick image preview), and quick is the right word: previews land in temp, so your output folder stays clean.

It's from Comfyui-LG_GroupExecutor, LAOGOU-666's small utility pack. This node is basically a reskin of the core SaveImage with format control bolted on and the output path moved to temp - nothing exotic, no dependencies, no models.

How it works

Under the hood it subclasses ComfyUI's SaveImage but writes to folder_paths.get_temp_directory() with a random _temp_xxxxx prefix so runs don't collide. The format and quality inputs map to Pillow save options:

• PNG - quality maps to a compression level (9 * (1 - quality/100)), so higher quality = lower compression. Also embeds prompt/metadata if enabled.
• JPEG - quality passed straight to Pillow (default 95) with optimize=True.
• WEBP - quality passed through.

Every image in the batch gets its own temp file, and the node reports them to the UI so you get thumbnails in the preview pane.

Inputs

• images (IMAGE) - anything with pixels.
• format - PNG / JPEG / WEBP.
• quality (1–100, default 95) - meaning differs per format, but "higher is better" holds across all three.

No outputs - it's a terminal preview node.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/LAOGOU-666/Comfyui-LG_GroupExecutor

or ComfyUI Manager → "Comfyui-LG_GroupExecutor", then restart.

Where it earns its keep

• Batch previews without trashing your output folder. If you're iterating on a 64-frame batch and only want to look, this keeps the filesystem tidy.
• JPEG for speed, PNG for fidelity. Quality 95 JPEG is a good default; drop to 70 and previews get noticeably lighter if you're reviewing a big batch.
• Don't use it when you actually want to save - this is a look-at-me node, and temp files aren't durable.