Internet DRAFT - draft-seantek-image-bmp
draft-seantek-image-bmp
Network Working Group S. Leonard
Internet-Draft Penango, Inc.
Intended Status: Informational October 23, 2014
Expires: April 26, 2015
The Windows Bitmap Media Type
draft-seantek-image-bmp-01
Abstract
This document registers the image/bmp media type for use with the
Windows Bitmap format (BMP), also known as Device-Independent Bitmap
(DIB). Originally designed for Microsoft Windows 2.0 and OS/2, these
bitmaps contain a single raster graphic in a variety of compressed or
uncompressed formats.
Status of this Memo
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Copyright Notice
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1. Introduction
Long before the invention of Portable Network Graphics (PNG),
Microsoft Corporation and IBM Corporation needed to record images in
a format that their applications and operating systems could easily
render on low-end machines (Intel 80286). The resulting "BMP" format
contains a single raster graphic with basic header fields that can be
easily mapped (or "blitted") to locations in memory. As computing
moved from 16-bit to 32-bit, BMP evolved to contain 32-bit
structures. As the 90s wore on, the venerable BMP got boosts with
support for additional color spaces, color profiles, and compression
formats. The same basic format can be used to convey 2-bit black-and-
white bitmaps with a 1-bit alpha mask from the '80s, and full-color
Ultra HD images on leading-edge displays. BMP is a building block of
other formats, including Windows Metafiles, Windows Icons, and
Windows Cursors.
Many implementations of BMP were created because of Windows'
commercial success in the 1990s. Usage of the format for interchange
has [[probably?]] declined since the advent of PNG (for lossless
raster graphics) and JPEG (for lossy raster graphics); however, a
large body of free and commercially available BMP artwork exists.
Since Windows Icons are a building block of "favicon.ico" Web
technology, an implementer would almost certainly need to support
this format for basic interoperability.
Microsoft publicly documented the BMP format as early as the 1992
Windows 3.1 SDK (in the Windows Metafile documentation). Since 2007
Microsoft has released the format specification [MS-WMF], which
includes most components of the Windows Bitmap format, under its Open
Specification Promise [MS-OSP]. See Section 2.2.2.9 of [MS-WMF]
(DeviceIndependentBitmap Object). BMP data begins with a
BITMAPFILEHEADER and is followed by one of the bitmap headers
(BITMAPINFOHEADER, BITMAPV4HEADER, or BITMAPV5HEADER), optional color
table data, bitmap data, and optional profile data, in that order
[BMPSTOR].
[[TODO: Maybe it is worth considering registering Windows cursors,
animated cursors, and (re-registering) icons.]]
The key word "SHOULD" in this document is to be interpreted as
described in [RFC2119].
3. Windows Bitmap Media Type Registration Application
Type name: image
Subtype name: bmp
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Required parameters: None.
Optional parameters: None.
Encoding considerations: Binary.
Security considerations:
Bitmaps have a mostly unremarkable security history.
Because BMP data can encapsulate JPEG or PNG data (BI_JPEG, BI_PNG
values of the Compression enumeration in Section 2.1.1.7 of [MS-
WMF]), the security considerations of JPEG and PNG processing may
also apply to BMP.
Interoperability considerations:
Uncompressed Windows Bitmaps can be rather large. If there is a
need to compress an image, modern applications SHOULD consider
emitting JPEG or PNG data instead of embedding them in BMP
payloads.
Published specification: [MS-WMF] and [BMPSTOR].
Applications that use this media type:
Office productivity applications; clip art applications; desktop
publishing applications; Web browsers; graphics processing
applications.
Fragment identifier considerations: None.
Additional information:
Magic number(s): 42 4D ("BM"), meaning "bitmap". The next
field (BITMAPFILEHEADER bfSize) is a
little-endian DWORD indicating the size
of the bitmap content in bytes.
File extension(s): .bmp, .dib
Macintosh file type code(s):
"BMP ", "BMPf", or "BMPp". Apple has promulgated a
uniform type identifier (UTI) of "com.microsoft.bmp".
Person & email address to contact for further information:
Sean Leonard <dev+ietf@seantek.com>
Restrictions on usage: None.
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Author/Change controller: Sean Leonard <dev+ietf@seantek.com>
Intended usage: COMMON
Provisional registration? No
3. IANA Considerations
IANA is asked to register the media type image/bmp in the Standards
tree using the application provided in Section 2 of this document.
4. Security Considerations
See the registration template for security considerations.
6. References
6.1. Normative References
[BMPSTOR] Microsoft Corporation, "Bitmap Storage",
MSDN ID dd183391, 2014,
<http://msdn.microsoft.com/library/dd183391>.
[MS-WMF] Microsoft Corporation, "Windows Metafile Format",
[MS-WMF], v20140502 (Rev 11.1), May 2014,
<http://msdn.microsoft.com/library/cc250370>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, RFC
6838, January 2013.
6.2. Informative References
[MS-OSP] Microsoft Corporation, "Open Specification Promise",
February 2007,
<http://www.microsoft.com/interop/osp/default.mspx>.
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Author's Address
Sean Leonard
Penango, Inc.
5900 Wilshire Boulevard
21st Floor
Los Angeles, CA 90036
USA
EMail: dev+ietf@seantek.com
URI: http://www.penango.com/
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