How to add width & height (resolution) on wordpress function?

You may be looking for WP_Customize_Cropped_Image_Control which has width and height parameters (along with flex_width and flex_height). This will then present you with the image dimensions when you select an image in the Customizer. For example, refer to how the Custom Logo control is registered in core:

$wp_customize->add_control( new WP_Customize_Cropped_Image_Control( $wp_customize, 'custom_logo', array(
    'label'         => __( 'Logo' ),
    'section'       => 'title_tagline',
    'priority'      => 8,
    'height'        => $custom_logo_args[0]['height'],
    'width'         => $custom_logo_args[0]['width'],
    'flex_height'   => $custom_logo_args[0]['flex-height'],
    'flex_width'    => $custom_logo_args[0]['flex-width'],
    'button_labels' => array(
        'select'       => __( 'Select logo' ),
        'change'       => __( 'Change logo' ),
        'remove'       => __( 'Remove' ),
        'default'      => __( 'Default' ),
        'placeholder'  => __( 'No logo selected' ),
        'frame_title'  => __( 'Select logo' ),
        'frame_button' => __( 'Choose logo' ),
    ),
) ) );

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