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HTML5 image upload preprocessing

韦小宝Original: 2017-11-21 11:05:311926browse

HTML5 Image upload preprocessing, a plug-in that only has HTML5 front-end upload page without background processing, you can use it directly ~ yes for HTML5 Interested friends can research it.

The style is a bit ugly, but it’s still okay

Code:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>PHP中文网</title>
</head>
<body>
    <script>
        window.onload = function () {
            var input = document.createElement(&#39;input&#39;);
            input.type = &#39;file&#39;;
            input.addEventListener(&#39;change&#39;, function () {
                var file = this.files[0];
                var img = document.createElement(&#39;img&#39;);
                img.src = window.URL.createObjectURL(file);
                img.onload = function () {
                    var canvas = document.createElement(&#39;canvas&#39;);
                    var ctx = canvas.getContext(&#39;2d&#39;);
                    var MAX_WIDTH = 150;
                    var MAX_HEIGHT = 200;
                    var width = img.width;
                    var height = img.height;

                    if (width > height) {
                        if (width > MAX_WIDTH) {
                            height *= MAX_WIDTH / width;
                            width = MAX_WIDTH;
                        }
                    } else {
                        if (height > MAX_HEIGHT) {
                            width *= MAX_HEIGHT / height;
                            height = MAX_HEIGHT;
                        }
                    }

                    canvas.width = width;
                    canvas.height = height;
                    ctx.drawImage(img, 0, 0, width, height);
                    document.body.appendChild(canvas);

                    var btn = document.createElement(&#39;button&#39;);
                    btn.innerHTML = &#39;上传&#39;;
                    document.body.appendChild(btn);
                    btn.addEventListener(&#39;click&#39;, function() {
                        /*
                            toBlob的兼容性问题使用
                             https://github.com/blueimp/JavaScript-Canvas-to-Blob 这个库，就可以解决
                        */
                        canvas.toBlob(function(blob) {
                            var form = new FormData();
                            form.append(&#39;file&#39;, blob);
                            fetch(&#39;/api/upload&#39;, {method: &#39;POST&#39;, body: form});
                        });
                    }, false);
                };

                // document.body.appendChild(img); 原始图片是不用展示出来的
            }, false);
            document.body.appendChild(input);
        };
    </script>
</body>

</html>

The above is the HTML5 image upload preset Processing, you can modify it and use it directly, or you can study it. For more articles and source codes, please go to PHP Chinese website to search

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