ImageObserver (Java SE 26 & JDK 26)
Description: declaration: module: java.desktop, package: java.awt.image, interface: ImageObserver
Keywords: java.awt.image.ImageObserver interface

# Interface ImageObserver

All Known Implementing Classes:
  `AbstractButton, AbstractColorChooserPanel, BasicArrowButton, BasicComboBoxRenderer, BasicComboBoxRenderer.UIResource, BasicComboPopup, BasicInternalFrameTitlePane, BasicInternalFrameTitlePane.SystemMenuBar, BasicSplitPaneDivider, BasicToolBarUI.DragWindow, Box, Box.Filler, Button, Canvas, CellRendererPane, Checkbox, Choice, Component, Container, DefaultListCellRenderer, DefaultListCellRenderer.UIResource, DefaultTableCellRenderer, DefaultTableCellRenderer.UIResource, DefaultTreeCellEditor.DefaultTextField, DefaultTreeCellEditor.EditorContainer, DefaultTreeCellRenderer, Dialog, FileDialog, Frame, JButton, JCheckBox, JCheckBoxMenuItem, JColorChooser, JComboBox, JComponent, JDesktopPane, JDialog, JEditorPane, JFileChooser, JFormattedTextField, JFrame, JInternalFrame, JInternalFrame.JDesktopIcon, JLabel, JLayer, JLayeredPane, JList, JMenu, JMenuBar, JMenuItem, JOptionPane, JPanel, JPasswordField, JPopupMenu, JPopupMenu.Separator, JProgressBar, JRadioButton, JRadioButtonMenuItem, JRootPane, JScrollBar, JScrollPane, JScrollPane.ScrollBar, JSeparator, JSlider, JSpinner, JSpinner.DateEditor, JSpinner.DefaultEditor, JSpinner.ListEditor, JSpinner.NumberEditor, JSplitPane, JTabbedPane, JTable, JTableHeader, JTextArea, JTextComponent, JTextField, JTextPane, JToggleButton, JToolBar, JToolBar.Separator, JToolTip, JTree, JViewport, JWindow, Label, List, MetalComboBoxButton, MetalComboBoxUI.MetalComboPopup, MetalFileChooserUI.FileRenderer, MetalFileChooserUI.FilterComboBoxRenderer, MetalInternalFrameTitlePane, MetalScrollButton, Panel, Scrollbar, ScrollPane, TextArea, TextComponent, TextField, Window`

public interface ImageObserver
An asynchronous update interface for receiving notifications about Image information as the Image is constructed.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final int`
  `ABORT`
  This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously was aborted before production was complete.
  `static final int`
  `ALLBITS`
  This flag in the infoflags argument to imageUpdate indicates that a static image which was previously drawn is now complete and can be drawn again in its final form.
  `static final int`
  `ERROR`
  This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously has encountered an error.
  `static final int`
  `FRAMEBITS`
  This flag in the infoflags argument to imageUpdate indicates that another complete frame of a multi-frame image which was previously drawn is now available to be drawn again.
  `static final int`
  `HEIGHT`
  This flag in the infoflags argument to imageUpdate indicates that the height of the base image is now available and can be taken from the height argument to the imageUpdate callback method.
  `static final int`
  `PROPERTIES`
  This flag in the infoflags argument to imageUpdate indicates that the properties of the image are now available.
  `static final int`
  `SOMEBITS`
  This flag in the infoflags argument to imageUpdate indicates that more pixels needed for drawing a scaled variation of the image are available.
  `static final int`
  `WIDTH`
  This flag in the infoflags argument to imageUpdate indicates that the width of the base image is now available and can be taken from the width argument to the imageUpdate callback method.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `imageUpdate(Image img, int infoflags, int x, int y, int width, int height)`
  This method is called when information about an image which was previously requested using an asynchronous interface becomes available.

- ## Field Details

  - ### WIDTH

    static final int WIDTH
    This flag in the infoflags argument to imageUpdate indicates that the width of the base image is now available and can be taken from the width argument to the imageUpdate callback method.
    See Also:
      - `Image.getWidth(ImageObserver)`
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### HEIGHT

    static final int HEIGHT
    This flag in the infoflags argument to imageUpdate indicates that the height of the base image is now available and can be taken from the height argument to the imageUpdate callback method.
    See Also:
      - `Image.getHeight(ImageObserver)`
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### PROPERTIES

    static final int PROPERTIES
    This flag in the infoflags argument to imageUpdate indicates that the properties of the image are now available.
    See Also:
      - `Image.getProperty(String, ImageObserver)`
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### SOMEBITS

    static final int SOMEBITS
    This flag in the infoflags argument to imageUpdate indicates that more pixels needed for drawing a scaled variation of the image are available. The bounding box of the new pixels can be taken from the x, y, width, and height arguments to the imageUpdate callback method.
    See Also:
      - `Graphics.drawImage(Image, int, int, ImageObserver)`
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### FRAMEBITS

    static final int FRAMEBITS
    This flag in the infoflags argument to imageUpdate indicates that another complete frame of a multi-frame image which was previously drawn is now available to be drawn again. The x, y, width, and height arguments to the imageUpdate callback method should be ignored.
    See Also:
      - `Graphics.drawImage(Image, int, int, ImageObserver)`
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### ALLBITS

    static final int ALLBITS
    This flag in the infoflags argument to imageUpdate indicates that a static image which was previously drawn is now complete and can be drawn again in its final form. The x, y, width, and height arguments to the imageUpdate callback method should be ignored.
    See Also:
      - `Graphics.drawImage(Image, int, int, ImageObserver)`
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### ERROR

    static final int ERROR
    This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously has encountered an error. No further information will become available and drawing the image will fail. As a convenience, the ABORT flag will be indicated at the same time to indicate that the image production was aborted.
    See Also:
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

  - ### ABORT

    static final int ABORT
    This flag in the infoflags argument to imageUpdate indicates that an image which was being tracked asynchronously was aborted before production was complete. No more information will become available without further action to trigger another image production sequence. If the ERROR flag was not also set in this image update, then accessing any of the data in the image will restart the production again, probably from the beginning.
    See Also:
      - `imageUpdate(Image, int, int, int, int, int)`
      - Constant Field Values

- ## Method Details

  - ### imageUpdate

    boolean imageUpdate(Image img, int infoflags, int x, int y, int width, int height)
    This method is called when information about an image which was previously requested using an asynchronous interface becomes available. Asynchronous interfaces are method calls such as getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver) which take an ImageObserver object as an argument. Those methods register the caller as interested either in information about the overall image itself (in the case of getWidth(ImageObserver)) or about an output version of an image (in the case of the drawImage(img, x, y, [w, h,] ImageObserver) call).

    This method should return true if further updates are needed or false if the required information has been acquired. The image which was being tracked is passed in using the img argument. Various constants are combined to form the infoflags argument which indicates what information about the image is now available. The interpretation of the x, y, width, and height arguments depends on the contents of the infoflags argument.

    The `infoflags` argument should be the bitwise inclusive OR of the following flags: `WIDTH`, `HEIGHT`, `PROPERTIES`, `SOMEBITS`, `FRAMEBITS`, `ALLBITS`, `ERROR`, `ABORT`.

    Parameters:
      `img` - the image being observed.
      `infoflags` - the bitwise inclusive OR of the following flags: `WIDTH`, `HEIGHT`, `PROPERTIES`, `SOMEBITS`, `FRAMEBITS`, `ALLBITS`, `ERROR`, `ABORT`.
      `x` - the x coordinate.
      `y` - the y coordinate.
      `width` - the width.
      `height` - the height.
    Returns:
      `false` if the infoflags indicate that the image is completely loaded; `true` otherwise.
    See Also:
      - `WIDTH`
      - `HEIGHT`
      - `PROPERTIES`
      - `SOMEBITS`
      - `FRAMEBITS`
      - `ALLBITS`
      - `ERROR`
      - `ABORT`
      - `Image.getWidth(ImageObserver)`
      - `Image.getHeight(ImageObserver)`
      - `Graphics.drawImage(Image, int, int, ImageObserver)`