How can we give arguments to the node in launch file?

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I am using ros2 dashing and making a launch file including cam2image. For cam2image node, I can select the resolution using command line "ros2 run image_tools cam2image -x 1280 -y 960"

I want to do the same thing in the launch file because the default resoltion for cam2image is 320*240 which is too low.

I have no idea how to pass the arguments to the node in launch file properly. There is no example in the document. It always give me the default resolution when I run the following launch file.

from launch import LaunchDescription
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration, ThisLaunchFileDir
from ament_index_python.packages import get_package_share_directory

from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        Node(
            package='image_tools',
            node_executable='cam2image',
            arguments=[{"width":1280, "height":960, "x":1280, "y":960}],
            parameters=[{"width":1280, "height":960, "x":1280, "y":960}],
            output='screen',
        ),
    ])