resizing images for better preview before download them

[Hirakamu]

Hi, I have installed my copyparty on my local server for publishing my photography shots. I have an issue with image previewing things.

Each photo I upload to the local server is around 2-5 MB with a resolution of 4948 x 3280.

After I upload it, the photo uses a preview with the same resolution (4948 x 3280), and I don't want it to be that big just for a preview.

And it's the same with videos.

There is a method that YouTube commonly uses for low-quality video streaming. They say that the video is recompiled for low quality, but I don't know the name of the feature. Maybe it will work on pictures.

Is there an option to provide a smaller preview to reduce bandwidth?

[Paresh-pk]

@Hirakamu
Hey,

I get what you mean. Having your browser try to load a dozen 5 MB photos just for a gallery view is a real pain and super slow.

The good news is copyparty can handle this for you. What you're looking for is a way to make smaller "previews" or "thumbnails" on the fly, and copyparty has flags for exactly that. It's the same idea YouTube uses, where they re-encode video for different qualities.

Here’s how you can set it up.

1. Get the Right Tool

First, you need a program called ffmpeg. It's a powerhouse for handling video and image conversions, and copyparty uses it to create the previews. You'll need to install it on your server.

Open your server's terminal and run one of these commands, depending on your OS:

• Debian or Ubuntu: sudo apt update && sudo apt install ffmpeg
• Fedora or CentOS: sudo dnf install ffmpeg
• Arch Linux: sudo pacman -S ffmpeg

2. Start copyparty with New Flags

Now, when you run copyparty, you just need to add a few arguments to your command to turn on the preview generation.

• --th-img: This tells it to make thumbnails for your photos.
• --th-v: This makes a single image thumbnail for your videos.
• --v-pvw: This is the one you were asking about for videos. It creates a smaller, re-encoded video preview that loads quickly.

So, your new startup command would look something like this:

copyparty --th-img --th-v --v-pvw -v /path/to/your/photos

Pro-tip: If you think the default 256px previews are too small, you can make them bigger. For example, to get 480px previews, you'd run:

copyparty --th-size 480 --v-pvw-size 480p --th-img --th-v --v-pvw -v /path/to/your/photos

The first time you load a folder, it might take a moment while copyparty generates all the previews. But it's smart—it saves them in a hidden .cpt_cache folder, so every visit after that will be super fast.

Give that a try. It should completely solve the issue with large previews and make your site much snappier.

[Hirakamu]

Thank you for the response, previously why I requested this feature for my file server, because I am self hosting at my home with 50Mbps bandwitdh, and the photos are almost 200 clients accessing my network, and I experienced downtime many times, hopefully this method is useful for me, thank you.

[icxes]

If you'd like to view the full pictures in smaller size and reduced (but still reasonable) quality, it's also possible to run programs on file upload. So if using some extra hard drive space isn't a huge problem, you could have a volume like /images/fullsize/ that runs a program (after first uploading the full size and quality picture) to resize and decrease the quality of those pictures (but still retain the original), then upload the reduced quality picture into /images/preview/, without you having to do anything aside from uploading normally.

This is explained in some detail here, and although there isn't an image-resizing hook in there at the time, it does sound like something reasonably useful enough to be implemented at some point in the future.

This way you would have your original full size and quality images at /images/fullsize/, but could show the more reasonably sized ones at /images/preview for the clients accessing them. Testing just now, I was able to reduce a 41Mb 5460x3774 PNG image to a 181Kb 2083x1440 WebP image, about 0.44% of the original (or alternatively about 226 times smaller, if my math is correct). The resulting image looks the same to me when not zoomed in, so it should work fine for previews.