wp_upload_bits Upload Specific Sizes Only

This is how you can limit the image upload size

function fineima() {
  if (isset($_POST['submit'])) {
    wp_upload_bits($_FILES['fileToUpload']['name'], null, file_get_contents($_FILES['fileToUpload']['tmp_name']));
  }
  echo '<form action="" method="post" enctype="multipart/form-data">
      <input type="file" name="fileToUpload" id="fileToUpload">
      <input type="submit" value="Upload Image" name="submit">
    </form>
  ';
}
function fineFileUploaderRenderer() {
  ob_start();
  fineimageUpload();
  return ob_get_clean();
}
add_shortcode('your_file_uploader', 'fineFileUploaderRenderer');