Comparing image files

This topic describes how to compare images using the Image Compare window.

1. Starting a image compare operation

You can start an image compare operation from either the WinMerge window or a Command Prompt window.

From the WinMerge window

Click FileOpen. Use the Select Files or Folders dialog to specify the left and right source images to compare. For more details about the Select Files or Folder dialog, see Opening files and folders.

From a Command Prompt window

Run WinMergeU.exe, which is in your WinMerge install directory. In your command arguments, include the left and right images to compare. For more information about using the command line, see Command line.

2. Image Compare window

WinMerge support many types of images and can highlight the differences with blocks. Overlaying of the pictures is also possible.

Image Compare Window

You can set the most options in the Location Pane:

2.1. Difference


With the check box Highlight you can enable or disable the highlighting of the image differences.


If the highlighting is enabled you can even make it blinking by checking the check box Blink.

Block Size

The slider Block Size defines the size of the blocks which highlighting the image differences.

Block Alpha

The Block Alpha slider defines how strong the alpha blending of the blocks is.

Color Distance Threshold

The slider CD sets the Color Distance Threshold which helps to ignore color differences.

Ins/Del Detection


  • None
  • Vertical
  • Horizontal

2.2. Overlaying


Currently the following Overlay Modes are possible:

  • None
  • XOR
  • Alpha Blend
  • Alpha Blend Animation


The Alpha slider defines how strong the alpha blending of the overlay nodes Alpha Blend or Alpha Blend Animation is.

2.3. Zooming


With the Zoom slider you can zoom in or out of the images.


If the image format support multiple pages you can select the current page with the Page number box.