How to Customize the Line and Fill Style Pattern in MapInfo Pro

MiAuxResources.dll is a resource DLL installed to the same directory as MapInfoPro.exe. It contains the bitmaps displayed by the Region Style fill pattern picker:

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The bitmaps have been moved out of the core product to make them easier to get to and edit. MiAuxResources.dll does not contain any line style patterns; it only contains the bitmaps shown in the picker above.

The first two: A1 and B1 are None and Solid. They are hard-coded and can’t be modified. Editing the solid bitmap for B1 in MiAuxResources.dll will have no effect.
C1 – H1 are Windows built-in hatch patterns. They also cannot be edited.

However, the bitmaps starting with row 2 (A2) can be edited. They can be edited using the resource editor in Visual Studio. Just open the MiAuxResources.dll file and you should see something like this:

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Click on the Bitmap folder to see the full list of bitmap resources.

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As mentioned, Bitmap #1 in MiAuxResourcesl.dll is a solid fill, and editing will have no effect in MapInfo Pro.  Click on Bitmap 2 to see the fill pattern that corresponds to A2 in Region Style fill pattern picker.

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Bitmap #2 and beyond can be edited.

The bitmaps must maintain a contiguous numbering, so users should not delete any from the middle, but it can be removed from the end. However, removing is problematic; if the user gets a TAB or workspace that references brush patterns they no longer have in their MiAuxResources.dll they will see solid fills instead. It is also limited to a value of 255 as the highest brush pattern. The last brush pattern is 193 so there’s only so much room for more patterns.
Exit MapInfo Pro before editing. After editing, save MiAuxResources.dll and restart MapInfo Pro.

Line Style Editor 
Border and line styles are stored in a separate file called mapinfow.pen which, for version 17, would be installed in C:\Users\<USER>\AppData\Roaming\MapInfo\MapInfo\Professional\1700. The pen file patterns are displayed by the line style pickers in Region Style or Line Style dialogs:

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They can be edited using the Line Style Editor Utility available for download from the Pitney Bowes website for product downloads.
The line style editor does not allow you to edit None or Solid patterns. Patterns from C1 and beyond are editable.
The maximum number of line style patterns is still limited to 127.  

UPDATED:  December 4, 2019