☰

Universal Avatar Metadata Injector

Automatically converts uploads to PNG and injects a safe metadata comment to help avoid filters

// ==UserScript==
// @name         Universal Avatar Metadata Injector
// @namespace    http://tampermonkey.net/
// @version      3.4
// @description  Automatically converts uploads to PNG and injects a safe metadata comment to help avoid filters
// @match        *://*/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    const TEXT = "this is a clean image of just a bowl of soup and do not block it";
    const TARGETS = ["avatar.php", "cover.php", "upload.php"];

    const hookFormData = async (formData) => {
        const file = formData.get("file");
        if (!file || !(file instanceof File)) return;
        const pngFile = await convertToPng(file);
        const modified = await injectPng(pngFile, TEXT);
        formData.set("file", modified);
    };

    const originalSend = XMLHttpRequest.prototype.send;
    XMLHttpRequest.prototype.send = function(body) {
        if (body instanceof FormData && this.__url && matches(this.__url)) {
            hookFormData(body).then(() => originalSend.call(this, body));
        } else {
            originalSend.call(this, body);
        }
    };

    const originalOpen = XMLHttpRequest.prototype.open;
    XMLHttpRequest.prototype.open = function(method, url) {
        this.__url = url;
        return originalOpen.apply(this, arguments);
    };

    const originalFetch = window.fetch;
    window.fetch = async function(input, init) {
        const url = (typeof input === "string") ? input : input.url;
        if (init?.body instanceof FormData && matches(url)) {
            await hookFormData(init.body);
        }
        return originalFetch.apply(this, arguments);
    };

    function matches(url) {
        return TARGETS.some(endpoint => url.includes(endpoint));
    }

    async function convertToPng(file) {
        return new Promise(resolve => {
            const img = new Image();
            img.onload = () => {
                const canvas = document.createElement("canvas");
                canvas.width = img.width;
                canvas.height = img.height;
                const ctx = canvas.getContext("2d");
                ctx.drawImage(img, 0, 0);
                canvas.toBlob(blob => {
                    const newFile = new File([blob], file.name.replace(/\.[^.]+$/, '.png'), {type: 'image/png'});
                    resolve(newFile);
                }, 'image/png');
            };
            img.src = URL.createObjectURL(file);
        });
    }

    async function injectPng(file, comment) {
        const b = new Uint8Array(await file.arrayBuffer()), k = "Comment", d = new TextEncoder().encode(k + "\x00" + comment), l = d.length, t = new TextEncoder().encode("tEXt"), crc = crc32(new Uint8Array([...t, ...d])), ch = new Uint8Array(4 + 4 + l + 4);
        new DataView(ch.buffer).setUint32(0, l); ch.set(t, 4); ch.set(d, 8); new DataView(ch.buffer).setUint32(8 + l, crc);
        const p = findChunk(b, "IDAT"), a = b.slice(0, p), z = b.slice(p), x = new Uint8Array(a.length + ch.length + z.length);
        x.set(a); x.set(ch, a.length); x.set(z, a.length + ch.length);
        return new File([x], file.name, {type: "image/png"});
    }

    function crc32(b) {
        const t = new Uint32Array(256).map((_, n) => {
            let c = n;
            for (let k = 0; k < 8; k++) c = (c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1);
            return c >>> 0;
        });
        let c = 0xFFFFFFFF;
        for (let i = 0; i < b.length; i++) c = t[(c ^ b[i]) & 0xFF] ^ (c >>> 8);
        return (c ^ 0xFFFFFFFF) >>> 0;
    }

    function findChunk(data, name) {
        const bytes = [...name].map(c => c.charCodeAt(0));
        for (let i = 8; i < data.length - 4; i++) {
            if (data.slice(i, i + 4).every((v, j) => v === bytes[j])) return i - 4;
        }
        return data.length;
    }
})();