meta:
id: bmp
file-extension: bmp
xref:
forensicswiki: bmp
justsolve: BMP
loc: fdd000189
mime: image/bmp
pronom:
- fmt/114 # Windows Bitmap 1.0
- fmt/115 # Windows Bitmap 2.0
- fmt/116 # Windows Bitmap 3.0
- fmt/117 # Windows Bitmap 3.0 NT
- fmt/118 # Windows Bitmap 4.0
- fmt/119 # Windows Bitmap 5.0
- x-fmt/25 # OS/2 Bitmap 1.0
- x-fmt/270 # OS/2 Bitmap 2.0
wikidata: Q192869
tags:
- windows
license: CC0-1.0
ks-version: 0.9
endian: le
# ks-opaque-types: true # uncomment this line and comment `/types/bitmap`,
# if you provide an opaque type `bitmap` for bitmap data
doc: |
The **BMP file format**, also known as **bitmap image file** or **device independent
bitmap (DIB) file format** or simply a **bitmap**, is a raster graphics image file
format used to store bitmap digital images, independently of the display
device (such as a graphics adapter), especially on Microsoft Windows
and OS/2 operating systems.
## Samples
Great collection of various BMP sample files:
[**BMP Suite Image List**](
http://entropymine.com/jason/bmpsuite/bmpsuite/html/bmpsuite.html
) (by Jason Summers)
If only there was such a comprehensive sample suite for every file format! It's like
a dream for every developer of any binary file format parser. It contains a lot of
different types and variations of BMP files, even the tricky ones, where it's not clear
from the specification how to deal with them (marked there as "**q**uestionable").
If you make a program which will be able to read all the "**g**ood" and "**q**uestionable"
BMP files and won't crash on the "**b**ad" ones, it will definitely have one of the most
extensive support of BMP files in the universe!
## BITMAPV2INFOHEADER and BITMAPV3INFOHEADER
A beneficial discussion on Adobe forum (archived):
[**Invalid BMP Format with Alpha channel**](
https://web.archive.org/web/20150127132443/https://forums.adobe.com/message/3272950
)
In 2010, someone noticed that Photoshop generated BMP with an odd type of header. There wasn't
any documentation available for this header at the time (and still isn't).
However, Chris Cox (former Adobe employee) claimed that they hadn't invented any type
of proprietary header and everything they were writing was taken directly
from the Microsoft documentation.
It showed up that the unknown header was called BITMAPV3INFOHEADER.
Although Microsoft has apparently requested and verified the use of the header,
the documentation on MSDN has probably got lost and they have probably
forgotten about this type of header.
This is the only source I could find about these structures, so we could't rely
on it so much, but I think supporting them as a read-only format won't harm anything.
Due to the fact that it isn't documented anywhere else, most applications don't support it.
All Windows headers at once (including mentioned BITMAPV2INFOHEADER and BITMAPV3INFOHEADER):
## Specs
* [Bitmap Storage (Windows Dev Center)](
https://learn.microsoft.com/en-us/windows/win32/gdi/bitmap-storage
)
* BITMAPFILEHEADER
* BITMAPINFOHEADER
* BITMAPV4HEADER
* BITMAPV5HEADER
* [OS/2 Bitmap File Format](
https://www.fileformat.info/format/os2bmp/egff.htm
)
* BITMAPFILEHEADER (OS2BMPFILEHEADER)
* BITMAPCOREHEADER (OS21XBITMAPHEADER)
* OS22XBITMAPHEADER
* [Microsoft Windows Bitmap](
http://netghost.narod.ru/gff/graphics/summary/micbmp.htm
)
* BITMAPFILEHEADER (WINBMPFILEHEADER)
* BITMAPCOREHEADER (WIN2XBITMAPHEADER)
* BITMAPINFOHEADER (WINNTBITMAPHEADER)
* BITMAPV4HEADER (WIN4XBITMAPHEADER)
seq:
- id: file_hdr
type: file_header
- id: dib_info
size: file_hdr.ofs_bitmap - file_hdr._sizeof
type: bitmap_info
- id: bitmap
type: bitmap
size-eos: true
types:
bitmap:
doc: |
Replace with an opaque type if you care about the pixels. You can look at
an example of a JavaScript implementation:
<https://github.com/generalmimon/bmptool/blob/master/src/Bitmap.js>
There is a proposal for adding bitmap data type to Kaitai Struct:
<https://github.com/kaitai-io/kaitai_struct/issues/188>
file_header:
-orig-id: BITMAPFILEHEADER
doc-ref: https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapfileheader
seq:
- id: file_type
-orig-id: bfType
contents: "BM"
- id: len_file
-orig-id: bfSize
type: u4
doc: not reliable, mostly ignored by BMP decoders
- id: reserved1
-orig-id: bfReserved1
type: u2
- id: reserved2
-orig-id: bfReserved2
type: u2
- id: ofs_bitmap
-orig-id: bfOffBits
type: s4
doc: Offset to actual raw pixel data of the image
bitmap_info:
-orig-id: BITMAPINFO
doc-ref: https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapinfo
seq:
- id: len_header
type: u4
- id: header
-orig-id: bmciHeader
size: len_header - len_header._sizeof
type: bitmap_header(len_header)
- id: color_mask
type: color_mask(header.bitmap_info_ext.compression == compressions::alpha_bitfields)
if: is_color_mask_here
doc: Valid only for BITMAPINFOHEADER, in all headers extending it the masks are contained in the header itself.
- id: color_table
-orig-id: bmciColors
size-eos: true
type: 'color_table(not header.is_core_header, header.extends_bitmap_info ? header.bitmap_info_ext.num_colors_used : 0)'
if: not _io.eof
instances:
is_color_mask_here:
value: >-
not _io.eof
and header.len_header == header_type::bitmap_info_header.to_i
and (header.bitmap_info_ext.compression == compressions::bitfields or header.bitmap_info_ext.compression == compressions::alpha_bitfields)
is_color_mask_given:
value: >-
header.extends_bitmap_info
and (header.bitmap_info_ext.compression == compressions::bitfields or header.bitmap_info_ext.compression == compressions::alpha_bitfields)
and (is_color_mask_here or header.is_color_mask_here)
color_mask_given:
value: >-
is_color_mask_here
? color_mask
: header.color_mask
if: is_color_mask_given
color_mask_red:
value: >-
is_color_mask_given
? color_mask_given.red_mask
: header.bits_per_pixel == 16
? 0b11111_00000_00000
: header.bits_per_pixel == 24 or header.bits_per_pixel == 32
? 0xff_00_00
: 0
# ^ uses fixed color palette, so color mask is N/A
color_mask_green:
value: >-
is_color_mask_given
? color_mask_given.green_mask
: header.bits_per_pixel == 16
? 0b00000_11111_00000
: header.bits_per_pixel == 24 or header.bits_per_pixel == 32
? 0x00_ff_00
: 0
color_mask_blue:
value: >-
is_color_mask_given
? color_mask_given.blue_mask
: header.bits_per_pixel == 16
? 0b00000_00000_11111
: header.bits_per_pixel == 24 or header.bits_per_pixel == 32
? 0x00_00_ff
: 0
color_mask_alpha:
value: >-
is_color_mask_given and color_mask_given.has_alpha_mask
? color_mask_given.alpha_mask
: 0
bitmap_header:
-orig-id:
- BITMAPCOREHEADER
- OS21XBITMAPHEADER
doc-ref:
- https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapcoreheader
- https://www.fileformat.info/format/os2bmp/egff.htm#OS2BMP-DMYID.3.1
params:
- id: len_header
type: u4
seq:
- id: image_width
-orig-id: biWidth
type:
switch-on: is_core_header
cases:
true: u2
false: u4
doc: Image width, px
- id: image_height_raw
-orig-id: biHeight
type:
switch-on: is_core_header
cases:
true: s2
false: s4
doc: Image height, px (positive => bottom-up image, negative => top-down image)
- id: num_planes
-orig-id: biPlanes
type: u2
# valid: 1
doc: Number of planes for target device, must be 1
- id: bits_per_pixel
-orig-id: biBitCount
type: u2
doc: Number of bits per pixel that image buffer uses (1, 4, 8, 16, 24 or 32)
- id: bitmap_info_ext
type: bitmap_info_extension
if: extends_bitmap_info
- id: color_mask
type: color_mask(len_header != header_type::bitmap_v2_info_header.to_i)
if: is_color_mask_here
- id: os2_2x_bitmap_ext
type: os2_2x_bitmap_extension
if: extends_os2_2x_bitmap
- id: bitmap_v4_ext
type: bitmap_v4_extension
if: extends_bitmap_v4
- id: bitmap_v5_ext
type: bitmap_v5_extension
if: extends_bitmap_v5
instances:
is_core_header:
value: len_header == header_type::bitmap_core_header.to_i
extends_bitmap_info:
value: len_header >= header_type::bitmap_info_header.to_i
extends_os2_2x_bitmap:
value: len_header == header_type::os2_2x_bitmap_header.to_i
extends_bitmap_v4:
value: len_header >= header_type::bitmap_v4_header.to_i
extends_bitmap_v5:
value: len_header >= header_type::bitmap_v5_header.to_i
image_height:
value: 'image_height_raw < 0 ? -image_height_raw : image_height_raw'
bottom_up:
value: image_height_raw > 0
is_color_mask_here:
value: len_header == header_type::bitmap_v2_info_header.to_i
or len_header == header_type::bitmap_v3_info_header.to_i
or extends_bitmap_v4
uses_fixed_palette:
value: not (bits_per_pixel == 16 or bits_per_pixel == 24 or bits_per_pixel == 32)
and not (extends_bitmap_info and not extends_os2_2x_bitmap and (bitmap_info_ext.compression == compressions::jpeg or bitmap_info_ext.compression == compressions::png))
bitmap_info_extension:
-orig-id: BITMAPINFOHEADER
doc-ref: https://learn.microsoft.com/en-us/previous-versions/dd183376(v=vs.85)
seq:
- id: compression
-orig-id: biCompression
type: u4
enum: compressions
if: not _parent.extends_os2_2x_bitmap
- id: os2_compression
-orig-id: Compression
type: u4
enum: os2_compressions
if: _parent.extends_os2_2x_bitmap
- id: len_image
-orig-id: biSizeImage
type: u4
doc: |
If biCompression is BI_JPEG or BI_PNG, indicates the size of the JPEG or PNG image buffer.
This may be set to zero for BI_RGB bitmaps.
- id: x_resolution
-orig-id: biXPelsPerMeter
type: u4
- id: y_resolution
-orig-id: biYPelsPerMeter
type: u4
- id: num_colors_used
-orig-id: biClrUsed
type: u4
- id: num_colors_important
-orig-id: biClrImportant
type: u4
os2_2x_bitmap_extension:
-orig-id: OS22XBITMAPHEADER
doc-ref: https://www.fileformat.info/format/os2bmp/egff.htm#OS2BMP-DMYID.3.2
seq:
- id: units
type: u2
- id: reserved
type: u2
- id: recording
type: u2
# valid: 0
doc: |
Specifies how the bitmap scan lines are stored.
The only valid value for this field is 0, indicating that the bitmap is
stored from left to right and from the bottom up.
- id: rendering
type: u2
enum: os2_rendering
doc: Specifies the halftoning algorithm used on the bitmap data.
- id: size1
type: u4
doc: |
rendering == os2_rendering::error_diffusion
=> error damping as a percentage in the range 0 through 100
rendering == os2_rendering::panda or rendering == os2_rendering::super_circle
=> X dimension of the pattern used in pixels
- id: size2
type: u4
doc: |
rendering == os2_rendering::error_diffusion
=> not used
rendering == os2_rendering::panda or rendering == os2_rendering::super_circle
=> Y dimension of the pattern used in pixels
- id: color_encoding
type: u4
doc: |
Specifies the color model used to describe the bitmap data.
The only valid value is 0, indicating the RGB encoding scheme.
- id: identifier
type: u4
doc: Application-specific value
bitmap_v4_extension:
-orig-id: BITMAPV4HEADER
doc-ref: https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapv4header
seq:
- id: color_space_type
-orig-id: bV4CSType
type: u4
enum: color_space
- id: endpoint_red
type: cie_xyz
- id: endpoint_green
type: cie_xyz
- id: endpoint_blue
type: cie_xyz
- id: gamma_red
-orig-id: bV4GammaRed
type: fixed_point_16_dot_16
- id: gamma_blue
-orig-id: bV4GammaGreen
type: fixed_point_16_dot_16
- id: gamma_green
-orig-id: bV4GammaBlue
type: fixed_point_16_dot_16
cie_xyz:
-orig-id: CIEXYZ
doc-ref: https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-ciexyz
seq:
- id: x
type: fixed_point_2_dot_30
- id: y
type: fixed_point_2_dot_30
- id: z
type: fixed_point_2_dot_30
bitmap_v5_extension:
meta:
encoding: windows-1252 # for the file name of linked profile (see profile_data below)
-orig-id: BITMAPV5HEADER
doc-ref: https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapv5header
seq:
- id: intent
-orig-id: bV5Intent
type: u4
enum: intent
- id: ofs_profile
-orig-id: bV5ProfileData
doc: The offset, in bytes, from the beginning of the BITMAPV5HEADER structure to the start of the profile data.
type: u4
- id: len_profile
-orig-id: bV5ProfileSize
type: u4
- id: reserved
-orig-id: bV5Reserved
type: u4
instances:
has_profile:
value: >-
_parent.bitmap_v4_ext.color_space_type == color_space::profile_linked
or _parent.bitmap_v4_ext.color_space_type == color_space::profile_embedded
profile_data:
io: _root._io
pos: _root.file_hdr._sizeof + ofs_profile
size: len_profile
type:
switch-on: _parent.bitmap_v4_ext.color_space_type == color_space::profile_linked
cases:
true: strz
if: has_profile
doc-ref: https://learn.microsoft.com/en-us/windows/win32/wcs/using-structures-in-wcs-1-0 "If the profile is embedded,
profile data is the actual profile, and if it is linked, the profile data is the
null-terminated file name of the profile. This cannot be a Unicode string. It must be composed exclusively
of characters from the Windows character set (code page 1252)."
color_table:
params:
- id: has_reserved_field
type: bool
- id: num_colors
doc: |
If equal to 0, the pallete should contain as many colors as can fit into the pixel value
according to the `bits_per_pixel` field (if `bits_per_pixel` = 8, then the pixel can
represent 2 ** 8 = 256 values, so exactly 256 colors should be present). For more flexibility,
it reads as many colors as it can until EOS is reached (and the image data begin).
type: u4
seq:
- id: colors
type: rgb_record(has_reserved_field)
repeat: expr
repeat-expr: 'num_colors > 0 and num_colors < num_colors_present ? num_colors : num_colors_present'
instances:
num_colors_present:
value: '_io.size / (has_reserved_field ? 4 : 3)'
color_mask:
params:
- id: has_alpha_mask
type: bool
seq:
- id: red_mask
type: u4
- id: green_mask
type: u4
- id: blue_mask
type: u4
- id: alpha_mask
type: u4
if: has_alpha_mask
rgb_record:
-orig-id:
- RGB_TRIPLE
- RGB_QUAD
params:
- id: has_reserved_field
type: bool
seq:
- id: blue
type: u1
- id: green
type: u1
- id: red
type: u1
- id: reserved
type: u1
if: has_reserved_field
-webide-representation: "rgb({red:dec}, {green:dec}, {blue:dec})"
# Common types
fixed_point_2_dot_30:
-orig-id: FXPT2DOT30
seq:
- id: raw
type: u4
instances:
value:
value: (raw + 0.0) / (1 << 30)
-webide-representation: "{value}"
fixed_point_16_dot_16:
seq:
- id: raw
type: u4
instances:
value:
value: (raw + 0.0) / (1 << 16)
-webide-representation: "{value}"
enums:
compressions:
# https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapv5header (search for bV5Compression)
0:
id: rgb
-orig-id: BI_RGB
doc: Uncompressed RGB format
1:
id: rle8
-orig-id: BI_RLE8
doc: RLE compression, 8 bits per pixel
2:
id: rle4
-orig-id: BI_RLE4
doc: RLE compression, 4 bits per pixel
3:
id: bitfields
-orig-id: BI_BITFIELDS
4:
id: jpeg
-orig-id: BI_JPEG
doc: BMP file includes whole JPEG file in image buffer
5:
id: png
-orig-id: BI_PNG
doc: BMP file includes whole PNG file in image buffer
6:
id: alpha_bitfields
-orig-id: BI_ALPHABITFIELDS
doc: only Windows CE 5.0 with .NET 4.0 or later
doc-ref:
- https://en.wikipedia.org/wiki/BMP_file_format#DIB_header_(bitmap_information_header) table of compression methods
- http://entropymine.com/jason/bmpsuite/bmpsuite/html/bmpsuite.html q/rgba32abf.bmp
os2_compressions:
# https://www.fileformat.info/format/os2bmp/egff.htm#OS2BMP-DMYID.3.2
0:
id: rgb
1:
id: rle8
2:
id: rle4
3:
id: huffman_1d
doc: Huffman 1D compression (also known as CCITT Group 3 One-Dimensional (G31D))
4:
id: rle24
doc: RLE compression, 24 bits per pixel
os2_rendering:
0:
id: no_halftoning
1:
id: error_diffusion
2:
id: panda
doc: Processing Algorithm for Noncoded Document Acquisition (PANDA)
3:
id: super_circle
color_space:
# https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapv5header#members
# For BITMAPV4HEADER:
0:
id: calibrated_rgb
-orig-id: LCS_CALIBRATED_RGB
doc: This value implies that endpoints and gamma values are given in the appropriate fields.
0x73524742: # 'sRGB'
id: s_rgb
-orig-id: LCS_sRGB
doc: Specifies that the bitmap is in sRGB color space.
0x57696e20: # 'Win '
id: windows
-orig-id: LCS_WINDOWS_COLOR_SPACE
doc: This value indicates that the bitmap is in the system default color space, sRGB.
# For BITMAPV5HEADER:
0x4c494e4b: # 'LINK'
id: profile_linked
-orig-id: PROFILE_LINKED
doc: |
This value indicates that bV5ProfileData points to the file name of the profile
to use (gamma and endpoints values are ignored).
If a profile is linked, the path of the profile can be any fully qualified name
(including a network path) that can be opened using the Win32 CreateFile function.
0x4d424544: # 'MBED'
id: profile_embedded
-orig-id: PROFILE_EMBEDDED
doc: |
This value indicates that bV5ProfileData points to a memory buffer that contains
the profile to be used (gamma and endpoints values are ignored).
intent:
# https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapv5header#members
8:
id: abs_colorimetric
-orig-id: LCS_GM_ABS_COLORIMETRIC
doc: Maintains the white point. Matches the colors to their nearest color in the destination gamut.
1:
id: business
-orig-id: LCS_GM_BUSINESS
doc: Maintains saturation. Used for business charts and other situations in which undithered colors are required.
2:
id: graphics
-orig-id: LCS_GM_GRAPHICS
doc: Maintains colorimetric match. Used for graphic designs and named colors.
4:
id: images
-orig-id: LCS_GM_IMAGES
doc: Maintains contrast. Used for photographs and natural images.
header_type:
# https://web.archive.org/web/20190527043845/https://forums.adobe.com/servlet/JiveServlet/showImage/2-3273299-47801/BMP_Headers.png
12: bitmap_core_header
40: bitmap_info_header
52: bitmap_v2_info_header
56: bitmap_v3_info_header
64: os2_2x_bitmap_header
108: bitmap_v4_header
124: bitmap_v5_header
