Use ‘add_theme_support’ instead of ‘add_custom_image_header’ In WordPress 3.4

Please read Updating Custom Backgrounds and Custom Headers for WordPress 3.4.

Custom Headers

Old method:

// Define default header image constant
define( 'HEADER_IMAGE', get_template_directory_uri() . '/images/headers/default.jpg' );
// Define header image width constant
define( 'HEADER_IMAGE_WIDTH', 1000 );
// Define header image height constant
define( 'HEADER_IMAGE_HEIGHT', 198 );
// Define header text constant
define( 'NO_HEADER_TEXT', false );
// Define header text color constant
define( 'HEADER_TEXTCOLOR', '000' );
// Turn on random header image rotation by default.
// Requires HEADER_IMAGE to be null
add_theme_support( 'custom-header', array( 'random-default' => true ) );

// Add Theme support
add_custom_image_header( $wphead_cb, $adminhead_cb, $adminpreview_cb );

New method:

add_theme_support( 'custom-header', array(
    // Header image default
    'default-image'         => get_template_directory_uri() . '/images/headers/default.jpg',
    // Header text display default
    'header-text'           => false,
    // Header text color default
    'default-text-color'        => '000',
    // Header image width (in pixels)
    'width'             => 1000,
    // Header image height (in pixels)
    'height'            => 198,
    // Header image random rotation default
    'random-default'        => false,
    // Template header style callback
    'wp-head-callback'      => $wphead_cb,
    // Admin header style callback
    'admin-head-callback'       => $adminhead_cb,
    // Admin preview style callback
    'admin-preview-callback'    => $adminpreview_cb
) );

Again: that was easy, wasn’t it?

Just to clarify, here are the old-constant/new-array-key equivalents:

HEADER_IMAGE       => 'default-image'
HEADER_IMAGE_WIDTH  => 'width'
HEADER_IMAGE_HEIGHT => 'height'
NO_HEADER_TEXT      => 'header-text'
HEADER_TEXTCOLOR    => 'default-text-color'

All of the same callbacks are supported, exactly as before.

For reference, here is the complete defaults array:

$defaults = array(
    'default-image' => '',
    'random-default' => false,
    'width' => 0,
    'height' => 0,
    'flex-height' => false,
    'flex-width' => false,
    'default-text-color' => '',
    'header-text' => true,
    'uploads' => true,
    'wp-head-callback' => '',
    'admin-head-callback' => '',
    'admin-preview-callback' => '',
);