This plugin displays the pixel values at the cursor and its surroundings.

Also see the Pixel Inspector Tool (based on this plugin), which is usually more handy than this plugin.

The plugin displays the pixel values of a square neighborhood around the current cursor position as a table. The position can be fixed by a keystroke; in this case the last cursor position is used further on and marked in the image. The arrow keys nudge this position if the Pixel Inspector window is in the foreground. Use the fixed mode to examine how a filter changes the data (also during preview).

By default, the key switching between fixed mode and following the cursor is the ”!” key; it can be changed in the Preferences menu.

If the Pixel Inspector Window is in the foreground, “c” (also with any modifier keys, e.g. CTRL-C etc.) copies the current table of pixel values into the clipboard (tab-delimited).

In the table, the center position (current cursor) is printed in red (x, y and the value). Columns and row headers (x & y) are always raw pixel values, irrespective of any spatial calibration. The direction of the y axis is determined by Analyze>Set Measurements>Invert Y Coordinates). The pixel value readout depends on the preferences.

The Pixel Inspector panel closes automatically if the image is closed.

The Pixel Inspector in “fixed” mode. The red square shows where the pixels are read. Note that this square is independent of the selection (yellow).


For the Preferences menu, press the Prefs button at top left. Preferences items are stored in the IJ_Prefs.txt file.

  • Radius determines the size of the table, 3×3 for radius=1, 5×5 for radius=2 etc. The Pixel Inspector window must be closed and opened to get the new size.
  • Readout for grayscale 8&16 bit images can be raw, calibrated or hexadecimal.
  • Readout for RGB images can be R,G,B triples, gray value or hexadecimal.
  • The “fix position” key should be a key not used by ImageJ as a shortcut, e.g. ”!”. It can be a normal character key or F1 … F12.
  • The color of the square showing the position in fixed mode can be selected.
  • For copying the pixel values to the clipboard, it can be selected whether the current position (x,y) is not not written at all, written in the first line or in the same way as the header lines of the Pixel Inspector panel.

Pixel Inspector Preferences


  • Copy Pixel_Inspector.java into the ImageJ plugins folder or a subfolder thereof. Make sure you name the downloaded file ”Pixel_Inspector.java”; uppercase/lowercase matters.
  • Compile with “Compile and run” and press “OK”. Disregard any deprecation warning.

Limitations and known problems

  • Some image operations do not update the display (improved in ImageJ 1.39l).
  • If the image is in the foreground, sometimes the “fix position” key may not work. As a workaround, either click on the image with any area selection tool or keep the Pixel Inspector panel in the foreground.
  • The square showing the position in fixed mode disappears after operations that create their own image overlay. As a workaround, nudge the position back and forth (e.g. left and right arrow key). Also opening and closing the Prefs menu will repaint the square.

Version History

  • Version 2007-Dec-14 supports exponential format for pixel data
  • Version 2007-Dec-06 fixes a few bugs (update and calibration problems).
  • Version 2007-Dec-02 adds preferences, RGB readout, fixed mode, copy to clipboard.
plugin/utilities/pixel_inspector/start.txt · Last modified: 2012/02/14 19:21 by schmid
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