The resolution of photo’s increases every year. And while some of that information may be worthy of retaining, not all is. High resolution images come at a price. Not only storage, but, especially in a mobile context, also data transfer. In this post I explain how you could create an uploader that fixes this.

The old form

Traditionally your form would look something like this:

`<form enctype="multipart/form-data">
  <label for="image_upload">Upload image:</label>
  <input type="file" id="image_upload" name="image_upload"/>
  <input type="submit" />
</form>`

If you want to be forgiving to your end users (and not requiring them to manually resize the images themselves) you could configure your server to accept files > 20MB and resize the images server side.

However, to save bandwidth you you might want to resize the images just before uploading.

Enter canvas

To manipulate pixels we need a canvas. So we need a canvas element.

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