Converting HTML to images allows you to transform HTML content into static images that can be easily shared on social media, embedded in emails, or used as thumbnails in search engine results. This conversion process ensures that your content is displayed consistently across different devices and browsers, improving the overall user experience. In this article, you will learn how to convert HTML to images in React using Spire.Doc for JavaScript.
Install Spire.Doc for JavaScript
To get started with converting Word documents to PDF in a React application, you can either download Spire.Doc for JavaScript from our website or install it via npm with the following command:
npm i spire.doc
After that, copy the "Spire.Doc.Base.js" and "Spire.Doc.Base.wasm" files to the public folder of your project. Additionally, include the required font files to ensure accurate and consistent text rendering.
For more details, refer to the documentation: How to Integrate Spire.Doc for JavaScript in a React Project
Convert an HTML File to an Image in JavaScript
Spire.Doc for JavaScript allows you to load an HTML file and convert a specific page to an image stream using the Document.SaveImageToStreams() method. The image streams can then be further saved to a desired image format such as jpg, png, bmp, gif. The following are the main steps.
- Load the font file to ensure correct text rendering.
- Create a new document using the wasmModule.Document.Create() method.
- Load the HTML file using the Document.LoadFromFile() method.
- Convert a specific page to an image stream using the Document.SaveImageToStreams() method.
- Save the image stream to a specified image format.
- JavaScript
import React, { useState, useEffect } from 'react';
function App() {
// State to hold the loaded WASM module
const [wasmModule, setWasmModule] = useState(null);
// useEffect hook to load the WASM module when the component mounts
useEffect(() => {
const loadWasm = async () => {
try {
// Access the Module and spiredoc from the global window object
const { Module, spiredoc } = window;
// Set the wasmModule state when the runtime is initialized
Module.onRuntimeInitialized = () => {
setWasmModule(spiredoc);
};
} catch (err) {
// Log any errors that occur during loading
console.error('Failed to load WASM module:', err);
}
};
// Create a script element to load the WASM JavaScript file
const script = document.createElement('script');
script.src = `${process.env.PUBLIC_URL}/Spire.Doc.Base.js`;
script.onload = loadWasm;
// Append the script to the document body
document.body.appendChild(script);
// Cleanup function to remove the script when the component unmounts
return () => {
document.body.removeChild(script);
};
}, []);
// Function to convert an HTML file to an image
const HtmlToImage = async () => {
if (wasmModule) {
// Load the font file into the virtual file system (VFS)
await wasmModule.FetchFileToVFS('CALIBRI.ttf','/Library/Fonts/', `${process.env.PUBLIC_URL}/`);
// Specify the input and output file paths
const inputFileName = 'sample1.html';
const outputFileName = 'HtmlToImage.png';
// Fetch the input file and add it to the VFS
await wasmModule.FetchFileToVFS(inputFileName,'', `${process.env.PUBLIC_URL}/`);
// Create a new document
const doc = wasmModule.Document.Create();
// Load the HTML file
doc.LoadFromFile({fileName: inputFileName,fileFormat: wasmModule.FileFormat.Html,validationType: wasmModule.XHTMLValidationType.None});
// Save the first page as an image stream
let image = doc.SaveImageToStreams({pageIndex : 0, imagetype : wasmModule.ImageType.Bitmap});
// Save the image stream as a PNG file
image.Save(outputFileName);
// Read the generated image from VFS
const modifiedFileArray = wasmModule.FS.readFile(outputFileName);
// Create a Blog object from the image file
const modifiedFile = new Blob([modifiedFileArray], {type: 'image/png'});
// Create a URL for the Blob
const url = URL.createObjectURL(modifiedFile);
// Create an anchor element to trigger the download
const a = document.createElement("a");
a.href = url;
a.download = outputFileName;
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
URL.revokeObjectURL(url);
// Clean up resources
doc.Dispose();
}
};
return (
<div style={{ textAlign: 'center', height: '300px' }}>
<h1>Convert an HTML File to an Image Using JavaScript in React</h1>
<button onClick={HtmlToImage} disabled={!wasmModule}>
Convert
</button>
</div>
);
}
export default App;
Run the code to launch the React app at localhost:3000. Once it's running, click on the "Convert" button to download the image converted from an HTML file:
Below is the converted image file:
Convert an HTML String to an Image in JavaScript
To convert HTML strings to images, you'll need to first add HTML strings to the paragraphs of a Word page through the Paragraph.AppendHTML() method, and then convert the page to an image. The following are the main steps.
- Load the font file to ensure correct text rendering.
- Specify the HTML string.
- Create a new document using the wasmModule.Document.Create() method.
- Add a new section using the Document.AddSection() method.
- Add a paragraph to the section using the Section.AddParagraph() method.
- Append the HTML string to the paragraph using the Paragraph.AppendHTML() method.
- Convert a specific page to an image stream using the Document.SaveImageToStreams() method.
- Save the image stream to a specified image format.
- JavaScript
import React, { useState, useEffect } from 'react';
function App() {
// State to hold the loaded WASM module
const [wasmModule, setWasmModule] = useState(null);
// useEffect hook to load the WASM module when the component mounts
useEffect(() => {
const loadWasm = async () => {
try {
// Access the Module and spiredoc from the global window object
const { Module, spiredoc } = window;
// Set the wasmModule state when the runtime is initialized
Module.onRuntimeInitialized = () => {
setWasmModule(spiredoc);
};
} catch (err) {
// Log any errors that occur during loading
console.error('Failed to load WASM module:', err);
}
};
// Create a script element to load the WASM JavaScript file
const script = document.createElement('script');
script.src = `${process.env.PUBLIC_URL}/Spire.Doc.Base.js`;
script.onload = loadWasm;
// Append the script to the document body
document.body.appendChild(script);
// Cleanup function to remove the script when the component unmounts
return () => {
document.body.removeChild(script);
};
}, []);
// Function to convert an HTML string to an image
const HtmlStringToImage = async () => {
if (wasmModule) {
// Load the font file into the virtual file system (VFS)
await wasmModule.FetchFileToVFS('CALIBRI.ttf','/Library/Fonts/', `${process.env.PUBLIC_URL}/`);
// Specify the output file path
const outputFileName = 'HtmlStringToImage.png';
// Specify the HTML string
let HTML = "<html><head><title>HTML to Word Example</title><style>, body {font-family: 'Calibri';}, h1 {color: #FF5733; font-size: 24px; margin-bottom: 20px;}, p {color: #333333; font-size: 16px; margin-bottom: 10px;}";
HTML+="ul {list-style-type: disc; margin-left: 20px; margin-bottom: 15px;}, li {font-size: 14px; margin-bottom: 5px;}, table {border-collapse: collapse; width: 100%; margin-bottom: 20px;}";
HTML+= "th, td {border: 1px solid #CCCCCC; padding: 8px; text-align: left;}, th {background-color: #F2F2F2; font-weight: bold;}, td {color: #0000FF;}</style></head>";
HTML+="<body><h1>This is a Heading</h1><p>This is a paragraph demonstrating the conversion of HTML to Word document.</p><p>Here's an example of an unordered list:</p><ul><li>Item 1</li><li>Item 2</li><li>Item 3</li></ul>";
HTML+="<p>Here's a table:</p><table><tr><th>Product</th><th>Quantity</th><th>Price</th></tr><tr><td>Jacket</td><td>30</td><td>$150</td></tr><tr><td>Sweater</td><td>25</td><td>$99</td></tr></table></body></html>";
// Create a new document
const doc = wasmModule.Document.Create();
// Add a section to the document
let section = doc.AddSection();
// Add a paragraph to the section
let paragraph = section.AddParagraph();
// Append the HTML string to the paragraph
paragraph.AppendHTML(HTML.toString('utf8',0,HTML.length));
// Save the first page as an image stream
let image = doc.SaveImageToStreams({pageIndex : 0, imagetype : wasmModule.ImageType.Bitmap});
// Save the image stream as a PNG file
image.Save(outputFileName);
// Read the generated image from VFS
const modifiedFileArray = wasmModule.FS.readFile(outputFileName);
// Create a Blog object from the image file
const modifiedFile = new Blob([modifiedFileArray], {type: 'image/png'});
// Create a URL for the Blob
const url = URL.createObjectURL(modifiedFile);
// Create an anchor element to trigger the download
const a = document.createElement("a");
a.href = url;
a.download = outputFileName;
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
URL.revokeObjectURL(url);
// Clean up resources
doc.Dispose();
}
};
return (
<div style={{ textAlign: 'center', height: '300px' }}>
<h1>Convert an HTML String to an Image Using JavaScript in React</h1>
<button onClick={HtmlStringToImage} disabled={!wasmModule}>
Convert
</button>
</div>
);
}
export default App;
Get a Free License
To fully experience the capabilities of Spire.Doc for JavaScript without any evaluation limitations, you can request a free 30-day trial license.
