How Does Chrome\'s New Image Paste Feature Work?

Chrome's Image Paste Functionality: A Deeper Dive

Google's announcement of the ability to paste images from the clipboard directly into Gmail using Chrome 12 has sparked curiosity about the underlying mechanism.

Behind the Scenes: Clipboard API and Data Conversion

Contrary to previous assumptions, the enhancement lies not in the JavaScript paste event handling within WebKit, but in the newly implemented Clipboard API. This API allows developers to access the clipboard's contents, including images.

The code snippet provided demonstrates the core functionality:

<code class="javascript">document.onpaste = function (event) {
    var items = (event.clipboardData || event.originalEvent.clipboardData).items;
    ...
}</code>

Upon a paste event, the API's clipboardData.items provides a list of clipboard contents. If an item is of type file, it can be referred to as a Blob using getAsFile() and further processed using FileReader to retrieve a data URL for the image.

Extending Functionality

Once the data URL is obtained, it can be displayed on the page or uploaded to a server.

Important Note: The Clipboard API's items list can return a mime type for each item, which may prove useful in determining the nature of the clipboard contents.

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