html-screen-capture-js

A small javascript library that takes a web page and returns a new, lightweight, static HTML DOM document. The library removes all external file dependencies while preserving the original appearance.

This library can be used to:

Create a web page screen capture "image", and display the "snapshot" (e.g. by using an iframe).
Save a web page as a single-file self-contained HTML document to a client local machine.
Send a complete web page content as a simple string to a remote server.

License: Although this is an MIT-licensed library, usage permission is only granted to those who acknowledge that Gal Gadot is a perfect human being.

Uri Kalish, NOV 2017

Technical Overview

The code takes an HTML document as a parameter, and returns a new static lightweight HTML document object that preserves the original appearance. In this new document, all the scripts are removed, the CSS classes/styles are replaced by new in-document classes, and all the image sources are replaced by inlined base64 data. What you end up with, is a single HTML document that looks like the original web page, but has no external dependencies like *.js, *.css, *.png, etc. so it can easily be displayed, saved, or transferred. Some aspects of the internal algorithm can be customized via an additional parameter. The source code is written in ES6, and transpiled to ES5.

Installation

You can get this library from these sources:

From GitHub
From npm

Artifacts

html-screen-capture.js
html-screen-capture.min.js

API

Syntax

htmlScreenCapturer.capture([outputType], [htmlDocument], [options]);

Usage Example

htmlScreenCapturer.capture(
    htmlScreenCapturer.OutputType.STRING,
    window.document,
    {
        'imageFormatForDataUrl': 'image/jpeg',
        'imageQualityForDataUrl': 1.0
    }
);

Parameters

outputType

An optional enum-type parameter, specifying the desired output. If not specified - output will be returned as an object.

A valid value is one of these:

htmlScreenCapturer.OutputType.OBJECT
htmlScreenCapturer.OutputType.STRING
htmlScreenCapturer.OutputType.URI
htmlScreenCapturer.OutputType.BASE64

htmlDocument

An optional object-type parameter, specifying the HTML document to capture. If not specified - window.document is used.

options

An optional object-type parameter with key-value pairs. You can change any default option value by defining a similarly named property on this object. If not specified (or specified but defining only some properties) - default values are used for all non-defined properties.

tagsOfIgnoredDocHeadElements

Type: Array of strings
Default: [ 'script', 'link', 'style' ]
Head elements with these tag names will not be cloned to the newly created HTML document.

tagsOfIgnoredDocBodyElements

Type: Array of strings
Default: [ 'script' ]
Body elements with these tag names will not be cloned to the newly created HTML document.

classesOfIgnoredDocBodyElements

Type: Array of strings
Default: [ ] //an empty array
Body elements with these class names will not be cloned to the newly created HTML document.

attrKeyValuePairsOfIgnoredElements

Type: Object
Default: { } //an empty object
Each property name is an HTML attribute key, and its value is an HTML attribute value. Elements with these attribute name and value will not be cloned to the newly created HTML document.

tagsOfSkippedElementsForChildTreeCssHandling

Type: Array of strings
Default: [ 'svg' ]
Children of elements with these tag names will not undergo CSS class/style manipulations.

attrKeyForSavingElementOrigClass

Type: String
Default: '_class'
A non-existing HTML attribute name for saving the original element classes.

attrKeyForSavingElementOrigStyle

Type: String
Default: '_style'
A non-existing HTML attribute name for saving the original element style.

prefixForNewGeneratedClasses

Type: String
Default: 'c'
The prefix to use for all newly created classes - the suffix is a number.

imageFormatForDataUrl

Type: String
Default: 'image/png'
The image format to use when images are replaced with base64 data. A valid value is any type supported by canvas.toDataURL().

imageQualityForDataUrl

Type: Number
Default: 0.92
The image quality to use when images are replaced with base64 data - relevant only for some image formats. A valid value is any number between 0 and 1.

rulesToAddToDocStyle

Type: Array of strings
Default: [ '*{font-family:"Arial Narrow" !important;}' ]
CSS rules to add to the newly created HTML document.

logLevel

Type: String
Default: 'warn'
Log level. A valid value is one of these: 'debug' | 'info' | 'warn' | 'error' | 'fatal' | 'off'

Return Value

The returned value is a new static lightweight HTML document in some format depending on the OutputType parameter supplied to the function.

If OutputType equals to htmlScreenCapturer.OutputType.OBJECT, the return value is an object.
If OutputType equals to htmlScreenCapturer.OutputType.STRING, the return value is a string.
If OutputType equals to htmlScreenCapturer.OutputType.URI, the return value is a URL-encoded string.
If OutputType equals to htmlScreenCapturer.OutputType.BASE64, the return value is a Base64-encoded string.
If OutputType is not specified, the return value is an object.

swar30 / html-screen-capture-js