h4 // Image Compressor

H4_ImageCompressor is the "shrink this image" node for when you want to ship a result somewhere that doesn't love a 12MB PNG. It takes an image in, re-encodes it to JPEG, PNG, or WebP at a quality you pick, and hands you back the compressed image and the raw bytes and a string (the saved path or metadata). Save mode is on by default, so it can write the compressed file to disk for you - which makes it the natural terminal node for "generate a preview, compress it, push it somewhere" pipelines.

Under the hood it's straightforward Pillow work: _save_image_to_bytes encodes with the format's quality settings (JPEG quality, WebP method 6, PNG with compress_level 9), a background_color flattens alpha onto a solid color when you go to JPEG (which has no alpha channel), and the whole thing runs through the pack's preview/temp-asset system so you can see what you're compressing before you save. Nothing exotic - and that's the appeal: it's a boring, reliable re-encoder with a bytes output, which is rarer in ComfyUI than it should be.

The settings that matter

• image - the input image.
• quality - 1–100, default 85. Standard JPEG thinking: 85 is a great starting point, 70 for smaller files, 95+ for near-lossless.
• format - JPEG, PNG, or WebP. JPEG is the smallest for photos; PNG for anything needing lossless or transparency; WebP a good middle ground (the code even renders previews as WebP).
• show_preview / preview_only - look before you save; preview_only skips writing to disk entirely.
• save_mode / save_path - write the compressed file out (default on; save_path empty = the pack's default output location). If you just want bytes, turn save off.
• background_color - 255,255,255 by default. This is what alpha pixels get flattened to in formats without transparency, so if your WebP/PNG with transparency looks wrong after a JPEG conversion, this is why.

The outputs

• IMAGE - the compressed image tensor (for display or further use).
• BYTES - the encoded file bytes. This is the one you want if you're feeding an HTTP request, a cloud upload, or any node that accepts raw bytes.
• STRING - the saved path (or metadata string), for logging or feeding a filename downstream.

Installing

ComfyUI Manager → search "h4_Live", or:

cd ComfyUI/custom_nodes
git clone https://github.com/m3rr/h4_Live

restart. Needs Pillow, which every ComfyUI install already has.

Where people get burned

Two easy trips. First, going JPEG on an image with transparency: pick background_color deliberately or your transparent areas come back as white blocks. Second, forgetting save_mode is on by default - run a batch through it and your output folder quietly fills with compressed files you didn't ask for. And one honest note: quality 85 to 100 on a photorealistic image is usually invisible; the filesize difference is where you feel it. If you're compressing to post online, start at 85, and don't let anyone sell you on "quality 100 or it's trash."