http://vaaaaanquish.jp/doitu_no_tori/ 用Snippet

vaaaaaanquish_doitsunotori.js

(()=>{
    let responseImage = new Image();
    responseImage.style.maxWidth = "100%";
    responseImage.style.display = "block";
    let canvas = document.createElement("canvas");
    document.querySelector('body > form > input[type="submit"]').style.display = "none";
    document.getElementById("id_image").addEventListener("change", ev=>{
        let files = ev.target.files;
        if (!files.length || !files[0].type.match(/^image\/(png|gif|jpeg)$/))
            return;
        let reader = getDoitsuNoToriReader();
        reader.readAsDataURL(files[0]);
    })
    document.addEventListener("paste", ev=> {
        ev.preventDefault();
        let data = ev.clipboardData || window.clipboardData;
        for(let i=0; i<data.items.length; i++) {
            if(data.items[i].type.match(/^image\/(png|gif|jpeg)$/)) {
                let file = data.items[i].getAsFile();
                let reader = getDoitsuNoToriReader();
                reader.readAsDataURL(file);
            }
        }
    })
    document.body.appendChild(responseImage);
    function canvasToBlob(canvas, callback) {
        let type = "image/jpeg";
        if (canvas.toBlob) {
            canvas.toBlob(callback, type);
        } else if (canvas.toDataURL && window.Uint8Array && window.Blob && window.atob) {
            var binStr = atob(canvas.toDataURL(type).replace(/^[^,]*,/, ''))
              , len = binStr.length
              , arr = new Uint8Array(len);
            for (var i = 0; i < len; i++) {
                arr[i] = binStr.charCodeAt(i);
            }
            callback(new Blob([arr],{
                type: type
            }));
        } else {
            callback(null);
        }
    }
    function getDoitsuNoToriReader() {
        let reader = new FileReader();
        reader.addEventListener("load", ev=>{
            let img = new Image();
            img.addEventListener("load", ev=>{
                canvas.width = ev.target.width;
                canvas.height = ev.target.height;

                let c = canvas.getContext("2d");
                c.drawImage(ev.target, 0, 0);
                canvasToBlob(canvas, blob=>{
                    if (blob) {
                        let fd = new FormData(document.forms[0]);
                        fd.append("image", blob);
                        let xhr = new XMLHttpRequest();
                        xhr.open("POST", "");
                        xhr.responseType = "arraybuffer";
                        xhr.addEventListener("load", ev=>{
                            let urlCreator = window.URL || window.webkitURL;
                            let response = new Blob([ev.target.response],{
                                type: "image/png"
                            })
                            responseImage.src = urlCreator.createObjectURL(response);
                        }
                        )
                        xhr.send(fd);
                    }
                });
            }
            )
            img.src = ev.target.result
        })
        return reader;
    }
})()