resize image using javascript

Question

I\'m using javascript function to input image.

This is my HTML:

Answer 1

Resize it on the canvas like this:

function showimagepreview(input) { //image preview after select image
  if (input.files && input.files[0]) {
    var filerdr = new FileReader();

    filerdr.onload = function(e) {
      var img = new Image();

      img.onload = function() {
        var canvas = document.createElement('canvas');
        var ctx = canvas.getContext('2d');
        canvas.width = 250;
        canvas.height = canvas.width * (img.height / img.width);
        ctx.drawImage(img, 0, 0, canvas.width, canvas.height);

        // SEND THIS DATA TO WHEREVER YOU NEED IT
        var data = canvas.toDataURL('image/png');

        $('#imgprvw').attr('src', img.src);
        //$('#imgprvw').attr('src', data);//converted image in variable 'data'
      }
      img.src = e.target.result;
    }
    filerdr.readAsDataURL(input.files[0]);
  }
}

I haven't tested this yet, but it should work.

Resize image with javascript canvas (smoothly)