Editing BMP file format (section)

=== DIBs in memory ===
A bitmap image file loaded into memory becomes a DIB data structure – an important component of the Windows GDI API. The in-memory DIB data structure is almost the same as the BMP file format, but it does not contain the 14-byte bitmap file header and begins with the DIB header.  For DIBs loaded in memory, the color table can also consist of 16-bit entries that constitute indexes to the currently realized palette<ref name=BITMAPINFO>MSDN [http://msdn.microsoft.com/en-us/library/dd183375%28VS.85%29.aspx BITMAPINFO Structure]</ref> (an additional level of indirection), instead of explicit RGB color definitions.  In all cases, the pixel array must begin at a memory address that is a multiple of 4 bytes. In non-packed DIBs loaded in memory, the optional color profile data should be located immediately after the color table and before the gap1 and pixel array<ref name=DIBHeaderTypes/> (unlike in diag. 1).

When the size of gap1 and gap2 is zero, the in-memory DIB data structure is customarily referred to as "packed DIB" and can be referred to by a single pointer pointing to the beginning of the DIB header.  In all cases, the pixel array must begin at a memory address that is a multiple of 4 bytes. In some cases it may be necessary to adjust the number of entries in the color table in order to force the memory address of the pixel array to a multiple of 4 bytes.<ref name=BITMAPINFO/>  For "packed DIBs" loaded in memory, the optional color profile data should immediately follow the pixel array, as depicted in diag. 1 (with gap1=0 and gap2=0).<ref name=DIBHeaderTypes/><br>  "Packed DIBs" are required by [[Microsoft Windows|Windows]] clipboard API functions as well as by some Windows patterned brush and resource functions.<ref name=PackedDIB>Feng Yuan - Windows graphics programming: Win32 GDI and DirectDraw: [https://books.google.com/books?id=-O92IIF1Bj4C&pg=PA595 Packed Device-Independent Bitmap (CreateDIBPatternBrush, CreateDIBPatternBrushPt, FindResource, LoadResource, LockResource)]</ref>
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