Masks can be saved in a file, applied to the baseline and result bitmaps for you to examine on screen only, or applied to and saved in the baseline and result bitmap files. Once masks are applied and saved, they become a permanent part of the baseline and result bitmaps. The advantage of saving the mask alone is that later you can read in the mask file and apply it to the bitmap on screen, thus allowing you to keep the bitmap in its original state.
You can supply the name of a mask bitmap file (as well as its associated baseline bitmap file) as an argument to bitmap functions.
The Bitmap Tool supports the .msk file extension for mask files. Alternatively, you can designate a mask in the file name and use the generic .bmp extension. We recommend, however, that you use the .msk extension.
The following bitmap-related functions accept mask files as arguments:
The Open Agent and Classic Agent capture bitmaps in different color depths. By default, the Open Agent captures bitmaps using the current desktop settings for color depth. The Classic Agent captures bitmaps as 24-bit images. If you create a mask file for the captured bitmap using the Bitmap tool, the mask file is saved as a 24-bit bitmap. If the bitmap mask file does not have the same color depth as the bitmap that you capture, an error occurs. To ensure that VerifyBitmap functions do not fail due to different color-depth settings between the captured image and the mask image, ensure that the bitmaps have the same color depth.