Silk Test Classic always adds a bitmap footer to the bitmap file. This means that the physical size of the bitmap will be slightly bigger than if you capture the bitmap in the Bitmap Tool. The bitmap footer always contains the window tag for a given bitmap.
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.