Highlighting Text as Google Cloud Text-to-Speech Reads Aloud in Your Browser
Have you ever wanted to create a web application that reads text aloud and visually highlights the words being spoken? This can be incredibly useful for learning new languages, providing accessibility for users with visual impairments, or simply enhancing the user experience.
This article will guide you through the process of integrating Google Cloud Text-to-Speech (TTS) API with your web application to achieve this functionality.
The Scenario
Imagine you have a website where users can input text and have it read aloud. As the text is spoken, you want to highlight the currently spoken word on the screen to provide a more engaging and synchronized experience.
Initial Code Setup
Here's a basic code structure using JavaScript and the Google Cloud TTS API:
// 1. Initialize the Google Cloud TTS API client
const speech = new SpeechSynthesisUtterance();
// 2. Set the text to be spoken
speech.text = 'This text will be read aloud';
// 3. Configure the voice and language
speech.voice = speechSynthesis.getVoices().filter(voice => voice.name === 'en-US-Standard-A')[0];
speech.lang = 'en-US';
// 4. Create a function to handle speech synthesis
function speak() {
speechSynthesis.speak(speech);
}
// 5. Add event listeners for word boundaries
speech.onboundary = (event) => {
// Handle word boundary events here
// For example, update the highlight on the page
};
// 6. Call the speak function when needed
speak();
This code creates a basic speech synthesizer, but it lacks the dynamic highlighting of text as it is spoken.
Diving into the Details
To achieve the desired text highlighting, we'll need to use the onboundary event provided by the SpeechSynthesisUtterance object. This event is triggered at the end of each word in the spoken text.
Here's how we can leverage this event:
-
Identifying Word Boundaries: The
onboundaryevent provides acharIndexproperty. This indicates the character index of the current word in the spoken text. -
Highlighting the Text: We need to create a function that takes the
charIndexas input and dynamically highlights the corresponding word on the webpage. This could involve:- Selecting the correct DOM element containing the word.
- Adding a CSS class that applies the highlighting style.
Example Implementation
Let's modify the code to highlight the text dynamically:
// ... Previous code ...
speech.onboundary = (event) => {
const charIndex = event.charIndex;
// Assuming you have a function called 'highlightWord'
// This function handles the DOM manipulation to highlight the word
highlightWord(charIndex);
};
// Function to highlight the word based on charIndex
function highlightWord(charIndex) {
// Logic to select the corresponding word on the page based on charIndex
// and apply the necessary CSS class for highlighting
// For example:
const wordElement = document.querySelector(`span:nth-child(${charIndex})`);
wordElement.classList.add('highlighted');
}
// ... Rest of the code ...
This code will highlight the word on the screen as it is being spoken. It's important to customize the highlightWord function based on your HTML structure and CSS styles.
Additional Considerations
- Text Segmentation: If your text is long, you might want to split it into smaller segments to improve the performance of the highlighting process.
- User Experience: Consider adding visual cues like a progress bar to indicate the current progress of the speech synthesis.
- Accessibility: Ensure your implementation is accessible to users with disabilities. Provide alternative ways to interact with the content, such as text navigation or pausing/replaying functionality.
Summary
By integrating Google Cloud Text-to-Speech API with the onboundary event, you can create an interactive experience that reads text aloud and highlights the spoken words on your web application. This approach provides a more engaging, accessible, and user-friendly experience for your users.
Remember to adjust the code based on your specific needs and to design your application with accessibility in mind.
