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1994-04-17
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Generalised Bitmap Module
=========================
Supported File Formats
----------------------
Short name : Long name : File extensions
Comments
Bitmap : OS/2 1.1, 1.2, 2.0 / Windows 3.0 bitmap : .BMP .VGA .BGA .RLE .DIB .RL4 .RL8
Reads any of the above if uncompressed or run-length compressed.
Will not read CCITT G3 MH Fax compressed files.
Will not read 24 bit RLE files.
If input is an OS/2 bitmaparray file then which bitmap can be specified.
Input options: index=# (default: 0)
Can be made to write OS/2 1.1 or Windows 3.0 / OS/2 2.0 bitmaps
Output options: 1.1,win,2.0 (default: 2.0, note win=2.0)
The handling of 1bpp bitmaps is a little complicated.
When reading 1bpp bitmaps, the palette is ignored.
1's are considered foreground, and they are considered black.
0's are considered background, and they are considered white.
This agrees with WorkPlace Shell WPFolder background mode, and most PM
programs, but notably disagrees with Windows PBrush.
When writing 1bpp bitmaps, the actual 2 colours in the palette are
ignored, and a fixed palette is written. This is so that the resulting
bitmap will display black on white when displayed by WPFolder etc..
Foreground and background colours in palette can be inverted on input.
Input options: inv
Foreground and background colours in palette can be inverted on output.
Output options: inv
Foreground and background colours in bits can be inverted on input.
Input options: invb
Foreground and background colours in bits can be inverted on output.
Output options: invb
GIF : CompuServe Graphics Interchange Format : .GIF
Reads 1, bit data files.
Reads 2, 3 and 4 bit data files and presents them as 4 bit.
Reads 5, 6, 7 and 8 bit data files and presents them as 8 bit.
Writes 1, 4 and 8 bit data files.
Reads "GIF87a" and "GIF89a" style files.
Writes "GIF87a" style files.
Should correctly handle deferred clear-code in LZW data stream.
Will not generate output with deferred clear-code.
ie: should not break older GIF readers.
Can specify index of image within file on read.
Input option: index=# (default 0)
Can specify to return decoded data so far rather than error if corrupt.
Input option: errok
Can specify screen size to write in output screen descriptor.
Output options: xscreen=#,yscreen=# (defaults: image size).
Can specify background colour index to write in file BMHD header.
Output option: background=# (default: 0)
Can specify position information in output image descriptor.
Output options: xpos=#,ypos=# (defaults: 0,0).
Extensively test on GIF files from a wide variety of sources.
Compatibility tested with xloadimage and xv.
PCX : ZSoft PC Paintbrush Image format : .PCX
Reads and writes 1,4,8 and 24 bit colour files.
Subset of plane/bits-per-plane combinations supported.
Files are read and written using a run-length coding scheme.
Tested using Zsoft originated .PCX files.
Compressed runs of pixels are not supposed to straddle scan lines.
GBM never does this, but some other applications violate this rule.
By default, if GBM finds that a run of pixels is longer than the scan
line, it will use the leftover pixels on the next scan line.
Some images will not load properly, as they require the loading
program to discard those pixels in the run that extend beyond the end
of the scan line. This behaviour can be enabled in GBM.
Input option: trunc
TIFF : Microsoft/Aldus Tagged Image File Format support : .TIF
Reads and writes 1,4,8 and 24 bit colour files.
Can almost read all TIFF 6.0 Baseline compliant files.
Can read uncompressed and Packbits images.
CCITT Modified huffman compression is the missing peice.
Can read some files with extensions to Baseline.
Can read 1bpp greyscale and palettised files.
Can read Orientation==4 files.
Can read PlanarConfiguration==2 files for RGB image data.
Can read LZW compressed files too.
Can also read CMYK 4 colour seperation files.
No JPEG or Y-Cb-Cr support.
Writes files that comply with TIFF 6.0 Baseline.
Usually writes uncompressed files only.
Data is written out as a single large strip.
Can specify image within TIFF file with many images
Input option: index=# (default: 0)
Can write 1bpp as non-Baseline file preserving fg/bg cols
Output option: pal1bpp
Can ask for LZW compression.
Output option: lzw
Can specify informational tags to append on output.
Output options: artist=,software=,make=,model=,host=,documentname=,pagename=,imagedescription=
Targa : Truevision Targa/Vista bitmap : .TGA .VST .AFI
Reads any uncompressed type as 8 bit or 24 bit.
Reads both yup and ydown files.
Writes out as 8 bit or 16,24,32 bit.
Output options: 16,24,32 (default 24)
Can be made to write yup and ydown files.
Output options: ydown,yup (default: yup)
ILBM : Amiga IFF / ILBM Interleaved bitmap format : .IFF .LBM
Reads 1 bit palettised files.
Reads 2,3 and 4 bit palettised files, returning them as 4 bit.
Reads 5,6,7 and 8 bit palettised files, returning them as 8 bit.
Reads HAM6, HAM8, SHAM and Extra-Halfbrite images.
HAM6, HAM8 and SHAM returned as 24 bit data.
Writes 1,4 and 8 bit palettised colour files.
Writes 24 bit files by performing simple conversion to HAM6 first.
This loses quality but results are still better than 8 bit.
Understands the RLE compression scheme used.
Uses BMHD, CMAP, CAMG and BODY sections of file only.
Only writes BMHD, CMAP, CAMG and BODY sections in output files.
Can specify position information in file BHMD header.
Output options: xpos=#,ypos=# (defaults: 0,0).
Can specify transparent colour to write in file BMHD header.
Output option: transcol=# (default: 0)
Can specify aspect ratio to write in file BMHD header.
Output options: xaspect=#,yaspect=# (defaults: 1,1).
Can specify screen size to write in output BMHD header.
Output options: xscreen=#,yscreen=# (defaults: image size).
Note that when DeluxePaint etc. try to load an 8 bit IFF file, they
switch to a 32 colour (5 bit mode) and only read the 5 least
significant planes of the file - this generally looks yukky!
Tested using DeluxePaint sample bitmaps.
YUV12C : YUV12C M-Motion Frame Buffer : .VID
Reads files and presents data as 24 bit data.
Writes 24 bit data files by converting them into 12 bit YUV.
VID files MUST be a multiple of 4 pixels wide.
When writing a non-multiple of 4, the last 1, 2 or 3 pixels are lost.
Can specify image origin information in YUV12C header.
Output options: xpos=#,ypos=# (defaults: 0,0).
Tested using M-Control Program 2.0, Browser sample application.
Greymap : Portable Greyscale-map (binary P5 type) : .PGM
Credit for file format to Jef Poskancer.
No palette present in file format.
Reads 8 bit grey scale files.
Writes red, green, blue plane or greyscale equivelent of 8 bit image.
Output options: r,g,b,k (default: k)
Pixmap : Portable Pixel-map (binary P6 type) : .PPM
Credit for file format to Jef Poskancer.
Reads and writes 24 bit unpalettised RGB data files.
KIPS : IBM KIPS : .KPS
Reads 8 bit palettised files.
Will look for palette in .PAL file unless .KPL file specified.
Input options: pal,kpl (default: pal)
Writes 8 bit palettised files.
Will write palette in .PAL file unless .KPL file specified.
Output options: pal,kpl (default: pal)
IAX : IBM Image Access eXecutive : .IAX
Reads array as 8 bit greyscale.
File format does not hold image dimensions.
Hence code assumes width is 512 pixels unless overridden.
Input options: width=# (default: 512)
File format does not include palette.
Writes red, green, blue plane or greyscale equivelent of 8 bit image.
Output options: r,g,b,k (default: k)
XBitmap : X Windows bitmap : .XBM
Reads 1bpp X bitmaps, presenting 1's as black, 0's as white.
Writes 1bpp X bitmaps, darkest colours as 1's, brightest colour as 0's.
Tested upon some sample .XBM files.
Sprite : Archimedes Sprite format from RiscOS : .SPR .SPRITE
Technically sprite files have no extension, but GBM recognises .SPR.
Reads 1,4 and 8 bit sprites.
'First bit' value in header must be a multiple of 8 (v.likely).
Will only read image plane, will ignore any mask plane.
Will handle case when no palette present in file.
Will default to the default Wimp palette in this case.
If input contains more than one sprite then which can be specified.
Input options: index=# (default: 0)
Will output 1,4 and 8 bit files.
Will write a palette in the file.
Will only write an image plane, ie: no mask plane.
Will write a 16 entry palette for 8 bit data (not 64 entry).
Will map to wierd archmedes palette when writing 8 bit data.
Tested reading 4bpp sprites with no palette.
Tested reading 8bpp sprites with no palette and with 64 entry palette.
Sprites generated by GBM have been loaded on RiscOS.
Remember: Use SetType to change type of file from PC-file to Sprite,
by SetType option of filer menu or "*SetType <filename> Sprite".
PSEG : IBM Printer Page Segment : .PSE .PSEG .PSEG38PP .PSEG3820
This is a file format used by IBM document/printing systems.
It is used to represent a bi-level image to be used in a document.
Reads data and presents a 1bpp bitmap.
Image is presented 1's as black on 0's as white background.
PSEG files should be downloaded from a VM host in binary mode.
Some PSEG files have a corrupt record structure.
This doesn't cause a problem on VM but can confuse a non-VM reader.
GBM can be made to attempt to handle these files.
Input option: fixrec
Will output 1bpp file.
Can specify 2x scale factor.
Output option: double
Palette in 1bpp data is lost when written to file.
The resulting non-VM file has no record structure.
So when it is uploaded it must be fixed using FIXL3820 EXEC or similar.
Image width is rounded up to next multiple of 8 when written.
Sample Applications
-------------------
GBMHDR - Display header information from bitmap files
usage: gbmhdr [-g] [-s] {fn.ext{,opt}}
-g don't guess bitmap format, try each type
-s be silent about errors
fn.ext{,opt} input filenames (with any format specific options)
Bitmap when ext in [BMP VGA BGA RLE DIB RL4 RL8]
GIF when ext in [GIF]
PCX when ext in [PCX]
TIFF when ext in [TIF]
Targa when ext in [TGA VST AFI]
ILBM when ext in [IFF LBM]
YUV12C when ext in [VID]
Greymap when ext in [PGM]
Pixmap when ext in [PPM]
KIPS when ext in [KPS]
IAX when ext in [IAX]
XBitmap when ext in [XBM]
Sprite when ext in [SPR]
opt bitmap format specific option to pass to bitmap reader
Note that the GBM module only ever surfaces the size and bits per pixel
of images (regardless of the other information present in the header).
All GBM programs have access to the bitmap file formats documented
above, although this list is omitted in subsequent documentation.
GBMHDR displays output in the following style :-
384x768 8bpp 51Kb 17% GIF aab.gif
227x254 8bpp 58Kb 102% Bitmap andy.bmp
256x256 24bpp 84Kb 43% TIFF bardot.tif
Listed is the size, bits per pixel, Kb size of the file, a percentage
value, the file format, and the file name. The percentage is calculated
as (filesize*100/datasize) and effectively gives the compression ratio.
For example aab.gif is well compressed (to 17% of the theoretical
size). bardot.tif gives a >100% value because of the file header.
GBMREF - Reflect in horizontal and/or vertical directions
usage: gbmref [-h] [-v] [-t] fn1.ext{,opt} [fn2.ext{,opt}]
flags: -h reflect horizontally
-v reflect vertically
-t transpose x for y
fn1.ext{,opt} input filename (with any format specific options)
fn2.ext{,opt} optional output filename (or will use fn1 if not present)
bitmap formats and options as before
Certain non-obvious combinations of -h, -v and -t can be very usefull.
None of them can be used for just file format translation.
-h -v reflect both, equivelent to 180 degree turn
-h -t equivelent to 90 degree turn clockwise
-v -t equivelent to 90 degree turn anti-clockwise.
GBMSUB - Extract a subrectangle of a bitmap
usage: gbmsub [-x x] [-y y] [-w w] [-h h] fn1.ext{,opt} [fn2.ext{,opt}]
flags: -x x left edge of rectangle (default 0)
-y y bottom edge of rectangle (default 0)
-w w width of rectangle (default width of image - x)
-h h height of rectangle (default height of image - y)
fn1.ext{,opt} input filename (with any format specific options)
fn2.ext{,opt} optional output filename (or will use fn1 if not present)
bitmap formats and options as before
If none of the -x,-y,-w and -h options are supplied the defaults
cover the whole of the input file. Hence this program will just read
one file and write the data as another. Great for format conversion.
GBMSIZE - Change the size of a bitmap
usage: gbmsize [-w w] [-h h] fn1.ext{,opt} [fn2.ext{,opt}]
flags: -w w new width of bitmap (default width of bitmap)
-h h new height of bitmap (default height of bitmap)
fn1.ext{,opt} input filename (with any format specific options)
fn2.ext{,opt} optional output filename (or will use fn1 if not present)
bitmap formats and options as before
If none of the -w or -h options are supplied, the defaults will be
the input image size. Hence this program will just read one file and
write the data as another. Great for format conversion.
GBMBPP - Do various bits per pixel conversions
usage: gbmbpp [-m map] [-e] [-h] fn1.ext{,opt} [fn2.ext{,opt}]
flags: -m map mapping to perform (default 7x8x4)
bw black and white
vga 16 colour VGA
8 8 colour (in 4 bit file)
4g 4 bit greyscale
7x8x4 7 levels red, 8 green, 4 blue 8514/A
6x6x6 6 levels red, 6 green, 6 blue
8g 8 bit greyscale
tripel 64 reds, 64 greens, 64 blues tripel
freqR:G:B:N keep R red, G green, b blue bits, and map to
N most used colours in 8 bit palette
R:G:B keep R red, G green, B blue bits (eg: 8:8:8)
-e enable error-diffusion (default is to truncate)
-e not with -m 8g or tripel or freq or -h
-h enable halftoning (default is to truncate)
-h only with -m 7x8x4, 6x6x6, 8, vga or R:G:B, with no -e
fn1.ext{,opt} input filename (with any format specific options)
fn2.ext{,opt} optional output filename (or will use fn1 if not present)
bitmap formats and options as before
This program reads the input bitmap. If it is not 24 bit, then it is
expanded to 24 bit per pixel. The data is then processed using the
supplied mapping giving a 24,8,4 or 1 bit per pixel image, which is
then written to the output bitmap file. The bw mapping produces a 1
bpp output file, vga and 4g gives 4 bit output files, 7x8x4, 6x6x6, 8g,
freq and tripel give 8 bit output files. R:G:B (where R,G and B are
numbers in the range 0 to 8), gives a 24 bit output file where only
the top R bits of red are non-zero, the top G of green and B of blue.
The normal way to map is simply to map each colour in the source
bitmap to the closest one in the destination bitmap. However if -e
is supplied, error diffusion is used to get a smoother result. Also, if
-h is supplied halftoning may be used instead. -e and -h are not valid
together, and are only valid with certain mappings.
GBMGAMMA - Convert between various colour spaces
usage: gbmgamma [-m map] [-g gamma] [-s shelf] fn1.ext{,opt} [fn2.ext{,opt}]
flags: -m map mapping in the form ?_to_? (default: i_to_l), where ? is
i physical intensitys (eg: raytracer output)
p gamma corrected for a specific monitor
l L* cyclometric linear perceived intensitys (as in PM)
-g gamma set monitor gamma (default 2.1)
-s shelf set monitor shelf (default 0.0)
gamma and shelf only used for mapping to or from p
for 8514 monitor gamma=2.3,shelf=0.136
for 8515 monitor gamma=2.1,shelf=0.0
fn1.ext{,opt} input filename (with any format specific options)
fn2.ext{,opt} optional output filename (or will use fn1 if not present)
bitmap formats and options as before
This program reads a bitmap and assumes the pixel values in it are
in the input colour space. If the bitmap has a palette it maps each
palette entry according to the supplied mapping, otherwise it maps
each individual 24 bit pixel. For example, if you get a 24 bit per
pixel image from a Windows video capture program, the odds are in may
be in a gamma corrected colour space with a gamma of 2.2. You can
convert this to the L* cyclometric colour space used by PM by typing
"gbmgamma -m p_to_l -g 2.2 captured.bmp nicepm.bmp". The shelf option
is primarily for when converting to a gamma corrected colour space for
a specific monitor (when you aren't going to use PM to display the
bitmap, and the display program doesn't do any correction). Some
monitors don't actually start to light up pixels until the pixel
values are a certain value. The example of 0.136 for the 8514 monitor
says that pixel values 0 to 0.136*255=35 all come out equally black!
Normally "-s shelf" will not be used.
Colour spaces
-------------
If a light is physically twice as bright, the eye does not necessarily see it
as twice as bright. Also, if a pixel is written onto a monitor screen with
twice the value, the physical intensity of the pixel is not necessarily double.
How exactly should numbers inside a bitmap file relate to physical or
perceived intensitys when displayed on the screen?
In OS/2 PM perceived intensitys are proportional to the values in the bitmap
file. Pixels in such a bitmap are in the 'L* cyclometric' colour space.
Ray Tracers often write pixel values in the bitmap proportional to the physical
intensity computed for that ray. Such data is in the 'intensity' colour space.
Finally, if a bitmap holds values computed in such a way as to compensate for
the gamma of the monitor (ie: intensitys transformed to cancel out the gamma
of the monitor), then the data is in a 'gamma corrected' colour space.
So, if you have some Ray Tracer output, and you wish to display on an 8514
monitor WITHOUT using OS/2 PM, then to get a decent colour rendition, you must
map the bitmap from the 'intensity' to a 'gamma corrected' colour space.
To do this you must know the gamma of the 8514 monitor (which is about 2.1).
Also, if you have some Ray Tracer output, and you wish to display on OS/2 PM,
then to get a decent rendition you must map the bitmap from the 'intensity' to
the 'L* cyclometric' colour space.
GBMGAMMA is a colour mapping program capable of performing mappings between
any 2 of the 3 colour spaces above.
Mapping of this sort should really be done on 24 bit data, before
error-diffusion or halftoning takes place.
Some examples
-------------
gbmhdr *.bmp *.tif
Displays the headers of all the bitmaps and TIFF files
gbmref file.bmp file.tga
Perform no reflection (no -h, -v or -t).
Hence simply converts file from Bitmap to Targa format!
gbmref -h larrow.tga rarrow.tga
Reflects larrow.tga to make rarrow.tga
gbmref -h -t profit.gif loss.gif
The combination of a horizontal flip with a transpose gives a 90
degree rotation clockwise. Thus a graph going up from bottom left
to top right, ends up going from top left to bottom right!
gbmref -v uarrow.pcx "darrow.lbm,xaspect=5,yaspect=6,xscreen=320,yscreen=200"
Reflects uarrow.pcx to make darrow.lbm
Output options defined for ILBM files used to write to aspect ratio
and screen size fields in output .lbm file.
Note: some command processors (such as OS/2 CMD.EXE) will split command
line arguments at spaces and commas, so we quote second argument.
gbmsub -x 100 -y 50 page.bmp
Trims 100 pixels off the left, and 50 off of the bottom
Note: no second filename given, so output overwrites page.bmp
gbmsize -w 1024 -h 768 strangesize.bmp screensized.bmp
Takes any bitmap and scales it to a SVGA screen size.
gbmbpp -m 7x8x4 24bit.tga 8bit.bpp
Maps a 24 RGB image to the 8514/A PM palette
Note: Source image format (Targa) not same as output format (Bitmap)
gbmbpp -m 7x8x4 -h 24bit.bmp nice8bit.bmp
As above but with halftoning
gbmbpp -m 7x8x4 -e 24bit.bmp nice8bit.bmp
As above, but with error diffusion
gbmbpp -m vga -e 24bit.bmp nice4bit.bmp
As above, but suitable for VGA display
gbmbpp -m 5:5:5 -e 8r8g8b.tga "5r5g5b.tga,16"
Error diffuse from 24 bit RGB to 15 bit RGB
(bottom 3 bits of each of R,G and B become zero)
Output option ",16" ensures data written in Targa-16 form
This reduces wasted disk space.
gbmbpp -m freq8:8:8:240 24bit.bmp 8bit.bmp
Finds 240 most frequently used colours.
For other colours finds closest match in most common 240 colours.
Maps colours in 24bit.bmp to give 8 bit output file.
If excessively large number of colours in original, may truncate bits.
gbmgamma -m i_to_l raytrace.bmp pmsuited.bmp
raytrace.bmp has pixels values proportional to physical intensity
pmsuited.bmp is made with pixels proportional to perceived intensity
Source code
-----------
The main part of GBM is highly portable 32 bit C, and has been compiled on
OS/2 2.x, AIX 3.2 and other systems. Certain associated parts, notably the
GBMV and GBMV2 OS/2+PM programs are OS/2 dependant. Full source to these should
be available where you obtained this package.
Before compiling on OS/2, copy the os2 subdirectory to its parent. Similarly
for any other operating system.
The source code is folded, and was written using Andys Source Code Folding
Editor, which is also public domain, and should hopefully be available where
you obtained GBM.
Public domain declaration
-------------------------
I wrote all this code in my own time on my own equiptment.
I used public non-confidential information to do so.
I hereby place all this code into the public domain.
Feel free to do whatever you like with it.
No copyright / no royalties / no guarantees / no problem.
Caveat Emptor!
Obtaining this code
-------------------
Internet: ftp.cdrom.com: /pub/os2/2_x/graphics/gbm.zip
ftp.cdrom.com: /pub/os2/2_x/graphics/gbmsrc.zip
ftp-os2.nmsu.edu: /pub/os2/2_x/graphics/gbm.zip
ftp-os2.nmsu.edu: /pub/os2/2_x/graphics/gbmsrc.zip
IBM-VNET: REQUEST GBM FROM AKEY AT HVTVM5
REQUEST GBMSRC FROM AKEY AT HVTVM5
Earlier releases have been on the IBM OS/2 Developer Connection CD-ROMs 2 & 3.
Also, hopefully on the next Hobbes OS/2 Shareware CD-ROM.
Change Log
----------
11/5/92 Initial general release.
Various dates Fixed assorted bugs in various parts of GBM.
Dropped support for 16 bit systems.
Changed all code to now be compiled multithreaded.
Changed GBM library to a DLL under OS/2, saved at least 500Kb.
/NOI now required when linking with GBM.LIB.
Added textual error messages.
Accelerated halftoning and error-diffusion.
Added GIF, X Bitmap and RiscOS Sprite support.
Extensively improved TIFF file support (now almost Baseline).
Extensively improved IFF support (HAM6, HAM8 etc.).
GBM structure enlarged => PLEASE RECOMPILE
Addition of bitmap transpose (and hence rotate) capability.
Added GBMV2, the flagship OS/2+PM program to show off GBM.
28/9/93 Handling of 1bpp data has changed - now honors colours.
Windows / (OS/2 2.0 subset) not OS/2 1.1 bitmaps now default.
Improved error checking some file readers.
Addition of -s and -g options to GBMHDR.
11/11/93 Added F3 to close GBMV and GBMV2.
Fixed keyboard scrolling in GBMV2.
Added general (single level) Undo capability to GBMV2.
Added GBMWPOBJ.CMD to set up Workplace Shell Objects.
29/11/93 Sanitised documentation
Copy supplied to IBM OS/2 Developer Connection.
6/2/94 Removed max number of strips limitation in TIFF reader.
Added TIFF LZW encode option (alpha-level code).
Added percentage on GBMHDR listing.
1/4/94 Bugfix for speckley IFF file writing.
Bugfix for map to black and white.
Added support for PSEGs
18/4/94 Added GBMSCALE.LIB and GBMSIZE.EXE to resize bitmaps.
Rewrote a large chunk of GBMV2.EXE.
Added Paste, Resize... and Snapshot capability.
Added reflect selection only etc. capability
Removed Select All (now not required).
{{{ Andy Key
Internet: ak@vnet.ibm.com # Currently working at IBM until september 94
IBM-VNET: AKEY AT HVTVM5 # so addresses valid at least until then.