Convert WebP to PDF

WebP files end up needing to be PDFs for the same administrative reasons everything else does. A screenshot for a support ticket, a chart pulled off a dashboard, a product image for a supplier form, an image saved from a website that now has to be filed. The picture is right; the wrapper is wrong; and the system at the other end has an opinion about wrappers.

A PDF can carry JPEG data directly, so a JPEG goes into the document completely untouched — nothing decoded, nothing re-encoded, the same bytes in the file. A PNG does not have that privilege either: PDF has no PNG filter, so it is decoded and its pixels are deflated again. PDF has no idea what WebP is at all.

So this conversion decodes your image and stores the pixels in the document compressed losslessly, the way a PNG source is stored. No pixel value changes and nothing is compressed lossily, but the picture has been through a decode, which is one step more than the JPG route. On any real image you will not see it.

WebP is very good at compression and PNG is not, so the picture inside the PDF takes several times the space it did as a WebP. A 200 KB image becoming a 2 MB PDF is entirely normal and is not a sign that something went wrong.

If the size matters more than anything else — an upload limit, an email attachment — converting the WebP to a JPG first and then that to a PDF gives a much smaller document, at the cost of one extra lossy step and any transparency the image had.

This sets it apart from converting to JPG. PDF has a real understanding of alpha, so a cut-out logo or an icon with no background keeps it. Printed, that means it appears on white paper; placed into another document, it blends with whatever is behind it. If you wanted a solid background, add it before converting rather than hoping the PDF will supply one.

Fit-to-image gives you a page exactly the shape of the picture, with no border and nothing scaled, which is right for anything being uploaded. A4 or Letter centres it on a real sheet with a margin, which is right for anything being printed. The image is scaled down to fit when it is too large and never scaled up.

Everything happens in your browser: the WebP decoder and the PDF writer both run on your machine, and the file is not uploaded anywhere.

Most WebP files people convert were saved from a web page, which means they were sized for a web page — often eight hundred pixels wide, sometimes less. That is fine on screen and thin on paper: printed at A4 it works out at roughly seventy dots per inch, which looks soft.

Nothing in a conversion can add detail that was never downloaded. If the printed result matters, go back to the source and look for the full-size image before converting the version your browser happened to cache.

The image goes in as an image, so anything written in it stays a picture of writing: not selectable, not searchable, invisible to a screen reader. For a saved diagram or a chart that is usually irrelevant, and for a saved page of text it is the thing that matters most.

What you do gain is a fixed page at a fixed size that opens in a reader rather than in whatever the receiving machine decided handles images. That predictability is normally the entire reason the other end asked for a PDF.