在笔记本中保存<iframe>对象的屏幕截图？

Question

我正在插入<iframe ...>引用远程网站的对象,并在Chrome中为我提供笔记本中的交互式可视化(从简单方式到可视化Jupyter中的TensorFlow图形？).这样做的缺点是,当我关闭笔记本,然后再次打开它时,所有可视化都将被替换为空白空间.

我怀疑它显示需要重新执行javascript代码iframe.

另一个缺点是,当托管这个笔记本(即github)时,所有这些单元格都是空的,因此静态图像方法比重新执行javascript更具可移植性.

有人能看到一种方法来保存这些单元格的屏幕截图并将它们嵌入到笔记本中吗？也许类似的东西camera_ready(14)将嵌入来自输出单元14的可视化的静态屏幕截图.

Answer 1

PhantomJS可以帮助您进行屏幕捕获。当你的笔记本运行时，PhantomJS 浏览器将打开它并截取指定输出单元的屏幕截图：

PhantomJS 的 JS 文件：

// address of the notebook
var address = "http://localhost:8888/notebooks/Untitled.ipynb";
// auth token from Jupyter console
var authToken = "af6bc1d90688bb6c26aeb206b8690e4855d27ef8d265b1bc";
// cell number with a widget output
var cellNumber = 10;

// this function is used to verify that a page is fully loaded
// source: https://github.com/ariya/phantomjs/blob/master/examples/waitfor.js
function waitFor(testFx, onReady, timeOutMillis) {
    var maxtimeOutMillis = timeOutMillis ? timeOutMillis : 3000,
        start = new Date().getTime(),
        condition = false,
        interval = setInterval(function() {
            if ( (new Date().getTime() - start < maxtimeOutMillis) && !condition ) {
                // If not time-out yet and condition not yet fulfilled
                condition = (typeof(testFx) === "string" ? eval(testFx) : testFx());
            } else {
                if(!condition) {
                    // If condition still not fulfilled (timeout but condition is 'false')
                    console.log("'waitFor()' timeout");
                    phantom.exit(1);
                } else {
                    // Condition fulfilled (timeout and/or condition is 'true')
                    console.log("'waitFor()' finished in " + (new Date().getTime() - start) + "ms.");
                    typeof(onReady) === "string" ? eval(onReady) : onReady();
                    clearInterval(interval); //< Stop this interval
                }
            }
        }, 250); //< repeat check every 250ms
};

// log in to a notebook using a token
function logIn() {
    console.log("Logging in");
    page.evaluate(function(token) {
        document.forms[0].password.value = token;
        document.forms[0].submit();
    }, authToken);
}

// wait for a notebook to fully load, find the
// needed output cell and save it as a PNG file
function saveAsPNG() {
    console.log("Saving PNG")
    // Wait for 'notebook-container' to be visible
    waitFor(function() {
        // Check in the page if a specific element is now visible
        return page.evaluate(function() {
            return $("#notebook-container").is(":visible");
        });
    }, function() {
        console.log("The notebook-container element should be visible now.");
        var clipRect = page.evaluate(function(cell){
            // we are selecting only the output cell
            var searchStr = 'div.input_prompt:contains("[' + cell + ']:")';
            var parentCell = $(searchStr).parents('div.cell')[0];
            // get only the data div
            var outputSubarea = $(parentCell).find('div.output_subarea')[0];
            // get the coordinates of the data div
            return outputSubarea.getBoundingClientRect()
        }, cellNumber);

        page.clipRect = {
            top:    clipRect.top,
            left:   clipRect.left,
            width:  clipRect.width,
            height: clipRect.height
          };
       page.render('example.png');
       phantom.exit();
    });
}

var page = require('webpage').create();
// it seems, viewportSize should fully cover the
// the rendered div position, or nothing will be saved.
page.viewportSize = { width: 5000, height: 5000 };

page.open(address, function (status) {
    // Check for page load success
    if (status !== "success") {
        console.log("Unable to open a page");
    } else {
        // Wait for 'password_input' to be visible
        waitFor(function() {
            // Check in the page if a specific element is now visible
            return page.evaluate(function() {
                return $("#password_input").is(":visible");
            });
        }, function() {
           console.log("The password_input element should be visible now.");
           logIn();
           saveAsPNG();
        });
    }
});

在脚本中指定笔记本的地址、身份验证令牌和单元格编号，然后使用 phantomjs 运行它：

phantomjs script.js