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How to get the Data URI of an image?

Published in Web Development 4 mins read

You can obtain the Data URI (base64 encoded representation) of an image primarily through browser developer tools.

Here's how:

Using Browser Developer Tools (Chrome, Firefox, etc.)

This is the most common and straightforward method. Here's how to do it in Chrome (other browsers are similar):

  1. Inspect Element: Right-click on the image you want the Data URI for and select "Inspect" or "Inspect Element".
  2. Navigate to the Resources/Application/Source Panel: Look for tabs like "Sources" (in Chrome), "Application", or "Resources". Where the image shows up depends on how it's being used on the page.
  3. Find the Image: Locate the image file within the resources listed. You might have to explore different folders.
  4. Right-Click and Copy: Right-click on the image preview in the resources panel.
  5. Select "Copy as Data URI": The context menu will have an option specifically labeled "Copy as Data URI".
  6. Paste: Paste the copied Data URI wherever you need it.

Example of a Data URI:

data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w+r8qQI0AAAA//8AAAAAAAABAAAAR5KSOgAAABIAAAAAElFTkSuQmCC

Explanation:

  • data: - Indicates that this is a Data URI.
  • image/png - The MIME type of the image (e.g., image/jpeg, image/gif, image/svg+xml). This tells the browser what kind of data it is.
  • base64, - Indicates that the following data is base64 encoded.
  • iVBORw0KGgo... - The actual base64 encoded data of the image.

Programmatic Solutions (JavaScript)

You can also generate a Data URI using JavaScript, especially useful if you are dynamically manipulating images.

function getImageDataUri(img) {
  // Create an empty canvas element
  const canvas = document.createElement('canvas');
  canvas.width = img.width;
  canvas.height = img.height;

  // Copy the image contents to the canvas
  const ctx = canvas.getContext('2d');
  ctx.drawImage(img, 0, 0);

  // Get the Data URI
  const dataURI = canvas.toDataURL('image/png'); // You can specify the image type here
  return dataURI;
}

// Example usage:
const imgElement = document.getElementById('myImage'); // Replace 'myImage' with the actual ID
const dataUri = getImageDataUri(imgElement);
console.log(dataUri);

Explanation of JavaScript Code:

  1. getImageDataUri(img) Function: Takes an img element as input.
  2. Create Canvas: Creates a <canvas> element in memory.
  3. Set Dimensions: Sets the canvas dimensions to match the image.
  4. Get Context: Gets the 2D rendering context of the canvas.
  5. Draw Image: Draws the image onto the canvas.
  6. toDataURL(): The crucial method! It converts the canvas content (which now contains the image) into a Data URI. You can specify the image type (e.g., 'image/jpeg', 'image/png') as an argument. If you don't provide an argument, the default type is image/png.
  7. Return Data URI: Returns the generated Data URI.

When to Use Data URIs

Data URIs are useful for:

  • Reducing HTTP Requests: Embedding images directly in your HTML/CSS eliminates the need for separate image requests, potentially improving page load times, especially for small images.
  • Offline Access: Data URIs allow images to be displayed even when the user is offline (if the HTML/CSS containing them is cached).
  • Dynamic Image Generation: When you are creating images on the fly with JavaScript.

Caveats:

  • Increased File Size: Base64 encoding increases the size of the image data (roughly by 33%). This can negate the benefits of reduced HTTP requests if the image is large.
  • Caching Issues: Data URIs are typically cached along with the HTML/CSS file they are embedded in. If the image changes, the entire HTML/CSS file needs to be re-downloaded.
  • Browser Compatibility: While widely supported, older browsers might have limitations or performance issues with very large Data URIs.

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