Image resize before upload

In 2011, we can know do it with the File API, and canvas. This works for now only in firefox and chrome. Here is an example :

var file = YOUR_FILE,
    fileType = file.type,
    reader = new FileReader();

reader.onloadend = function() {
  var image = new Image();
      image.src = reader.result;

  image.onload = function() {
    var maxWidth = 960,
        maxHeight = 960,
        imageWidth = image.width,
        imageHeight = image.height;

    if (imageWidth > imageHeight) {
      if (imageWidth > maxWidth) {
        imageHeight *= maxWidth / imageWidth;
        imageWidth = maxWidth;
      }
    }
    else {
      if (imageHeight > maxHeight) {
        imageWidth *= maxHeight / imageHeight;
        imageHeight = maxHeight;
      }
    }

    var canvas = document.createElement('canvas');
    canvas.width = imageWidth;
    canvas.height = imageHeight;

    var ctx = canvas.getContext("2d");
    ctx.drawImage(this, 0, 0, imageWidth, imageHeight);

    // The resized file ready for upload
    var finalFile = canvas.toDataURL(fileType);
  }
}

reader.readAsDataURL(file);

There is multiple-technology-capable Plupload tool which declares that it can do resizing before upload, but I haven't tried it yet. I have also find a suitable answer in my question about binary image handling javascript libs.

You have several options:

1. Java
2. ActiveX (only on windows)
3. Silverlight
4. Flash
5. Flex
6. Google Gears (the most recent version is capable of resizing and drag and drop from your desktop)

I've done a lot of research looking for a similar solution to what you have described and there a lot of solutions out there that vary a lot in quality and flexibility.

My suggestion is find a solution which will do 80% of what you need and customize it to suit your needs.