add_filter('wp_handle_upload_prefilter','_limit_image_dimensions');

function _limit_image_dimensions( $file ) {
    $image = getimagesize($file['tmp_name']);

    $minimum = array(
        'width' => '400',
        'height' => '400'
    );

    $maximum = array(
        'width' => '2000',
        'height' => '2000'
    );
    $image_width = $image[0];
    $image_height = $image[1];

    $too_small = "Image dimensions are too small. Minimum size is {$minimum['width']} by {$minimum['height']} pixels. Uploaded image is $image_width by $image_height pixels.";
    $too_large = "Image dimensions are too large. Maximum size is {$maximum['width']} by {$maximum['height']} pixels. Uploaded image is $image_width by $image_height pixels.";

    if ( $image_width < $minimum['width'] || $image_height < $minimum['height'] ) {
        $file['error'] = $too_small; 
        return $file;
    }
    elseif ( $image_width > $maximum['width'] || $image_height > $maximum['height'] ) {
        $file['error'] = $too_large; 
        return $file;
    }
    else
        return $file;
}

function _limit_image_size($file) {

    $image_size = $file['size']/1024;

    $limit = 200; // size in kb

    $is_image = strpos($file['type'], 'image');

    if ( ( $image_size > $limit ) && ($is_image !== false) )
          $file['error'] = 'Your picture is too large. It has to be smaller than '. $limit .'KB';

          return $file;

}
add_filter('wp_handle_upload_prefilter', '_limit_image_size');