lucach / meta-png

JavaScript library to store and retrieve metadata in PNG files

meta-png

Simple, zero-dependencies NodeJS/JavaScript library to store and retrieve metadata in PNG files.

Installation

Use your favourite package manager

npm install meta-png
# or: yarn add meta-png

Usage

The library provides two functions to add a new metadata:

addMetadata(PNGUint8Array, key, value)  // stores the given key-value inside the PNG, provided as Uint8Array
addMetadataFromBase64DataURI(dataURI, key, value)  // stores the given key-value inside the PNG, provided as a Data URL string

and a function to get back the stored value:

getMetadata(PNGUint8Array, key)  // retrives the given key from a PNG provided as Uint8Array

Limitations

• tEXt chunks inside PNG files are meant to use the Latin-1 standard: using characters outside this charset may lead to unwanted behaviors
• No check is performed inside add functions to test whether a given key is already present in the file. If you need it, you can call getMetadata beforehand and assert that it gives back undefined.

meta-png's Issues

CRC checksum is wrong after adding metadata

Hi, I saw the following error from Imagemagick on an image I had modified identify -verbose updated.png:

identify: tEXt: CRC error `updated.png' @ warning/png.c/MagickPNGWarningHandler/1669.

Does the CRC checksum need to be updated after modifying the tEXt section?

The code was very simple: readFileSync then addMetadata with the key/value hello and 42, then writeFileSync to a new file.

Thanks for this excellent library!

Library corrupts PNG footer/end

Hello!

Thank you for the best JS library for writing PNG metadata!

I'm experiencing some image corruption when storing metadata.

Is there a specific version of node I should use to avoid this?

node --version
v16.14.0

Original

Metadata

meta-png v1.0.1 module issue?

I see the new meta-png v1.0.1 on https://www.npmjs.com/package/meta-png. When I do an npm install [email protected], I get only the package.json and the README.md. However, when I npm install [email protected], I get the package.json and the README.md, but also a 'dist' directory with the javascript files in it.

Is there an issue with the meta-png v1.0.1 module, at least the one on npmjs.com? Of course, I could have something messed up in my environment, but I reviewed my setup and I'm not seeing this issue with other modules, so I though it best to ask if anybody else is seeing this issue.

Thank you.

Library sometimes creates invalid pngs

Hey @lucach!

Sorry for me being here again, but one of my users found out an issue regarding png generation.

I'll link his description for better clarity:
FRSOURCE/cypress-plugin-visual-regression-diff#184 (comment)

There are example pngs to be downloaded at the end of his message.

I have confirmed that for some images indeed meta-png is generating invalid PNGs, but I'm not quite sure why yet. I'll will add a comment here if I find anything.

Please let me know if you know what might be the issue 🤞