Red Snapper

Red Snapper is a simple module that takes a screenshot of a webpage using headless Chrome and the Chrome Debugging Protocol.

Important: The latest version has been tested on macOS Catalina and Ubuntu 16.04 LTS

Usage

In the following example, Red Snapper will take a 300px by 600px screenshot of github.com. If content is outside of that area it is cropped.

const fs = require('fs');
const snap = require('red-snapper');

snap({
    url: 'https://github.com/',
    width: 300,
    height: 600,
    delay: 500,
    format: 'png'
}).then((data) => {
    fs.writeFileSync('screenshot.png', Buffer.from(data, 'base64'));
}).catch((error) => {
    console.error(error);
});

In some cases you may need to pass a custom header to bypass bot detection or to get the correct cache version on a page. Add the headers object and populate with the values you need. Warning headers and their values must be strings otherwise you will get a ProtocolError.

To set the user agent string use the separate userAgent config parameter.

const fs = require('fs');
const snap = require('red-snapper');

snap({
    url: 'https://github.com/',
    width: 300,
    height: 600,
    delay: 500,
    format: 'png',
    headers: {
        'x-custom-header': 'header value'
    },
    userAgent: 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)'
}).then((data) => {
    fs.writeFileSync('screenshot.png', Buffer.from(data, 'base64'));
}).catch((error) => {
    console.error(error);
});

To take multiple screenshots specify an array of delays. The delays happen sequentially. So for example if you want screenshots at 1 second, 5 seconds, and 8 seconds from a page load use an array with values of [1000,4000,3000]; The return object then becomes an array of buffers.

snap({
    url: 'https://github.com/',
    width: 300,
    height: 600,
    delay: [1000,4000,3000],
    format: 'png'
}).then((data) => {
    for(let i = 0; i < data.length; i++) {
        fs.writeFileSync('screenshot'+i+'.png', Buffer.from(data[i], 'base64'));
    }
}).catch((error) => {
    console.error(error);
});

Parameters

• url (string) - Path to website to screenshot. Use file:/// to load a local file.
• width (integer) - Width of the browser. Defaults to 1024px. (optional)
• height (integer) - Height of the browser. Defaults to 768px. (optional)
• delay (integer|array) - Number of milliseconds to wait after page load before taking a screenshot. If an array is specified several screenshots will be taken with delays taking place sequentially. (optional)
• format (string) - File format of the screenshot. Acceptable values are "png" or "jpeg". Defaults to PNGs. (optional)
• quality (integer) - Value between [0..100] and only used when format is jpeg. Defaults to 80. (optional)
• fullPage (boolean) - When set to true the height of the image will grow to expand the content of the page. Defaults to false. (optional)
• headers (object) - An object containing key-value pairs. (optional)
• userAgent (string) - A string representing the user agent to send to a website. (optional)