Because BMP contains the matrix stored row by row of pixels, each row will have those three portions of pixels: from left to right, red, yellow, blue
****************************************************
* Creating a 30 x 100 bitmap with
yellow background
* the leftmost 10 columns red,
the middle 10 columns yellow, and the rightmost 10 columns blue
****************************************************
* The midmap look like this:
* RRRRRRRRRRYYYYYYYYYYBBBBBBBBBB
* RRRRRRRRRRYYYYYYYYYYBBBBBBBBBB
* RRRRRRRRRRYYYYYYYYYYBBBBBBBBBB
* RRRRRRRRRRYYYYYYYYYYBBBBBBBBBB
* RRRRRRRRRRYYYYYYYYYYBBBBBBBBBB
* etc (100 times)
****************************************************
LOCAL loBmp,
lcTrailerZeros, lcRedPixel, lcRedRow
loBmp = CREATEOBJECT("bmpcreator")
loBmp.nWidth = 30
loBmp.nHeight = 100
* Each row of pixels must have as
a length in bytes a multiple of 4. If necessary a few CHR(0) are added
lcTrailerZeros = IIF(MOD( m.loBmp.nWidth
* 3,4) <> 0, REPLICATE(CHR(0),4 - MOD( m.loBmp.nWidth * 3,4)), "")
* One pixel has three bytes,
corresponding to RGB (Red is the rightmost, blue is the leftmost)
lcRedPixel = CHR(0) + CHR(0) + CHR(255)
* One pixel has three bytes,
corresponding to RGB (Red is the rightmost, blue is the leftmost)
lcYellowPixel = CHR(0) + CHR(255) + CHR(255)
* One pixel has three bytes,
corresponding to RGB (Red is the rightmost, blue is the leftmost)
lcBluePixel = CHR(255) + CHR(0) + CHR(0)
* One row contain loBmp.nWidth
npixels; DO NOT FORGET the trailing zeroes
* one row = 10 red pixels
followed by 10 yellow pixels followed by 10 blue pixels
lcRow = REPLICATE(m.lcRedPixel,
10) + REPLICATE(m.lcYellowPixel, 10) + REPLICATE(m.lcBluePixel, 10) +
m.lcTrailerZeros
* The BITMAP
loBmp.cBitmap = REPLICATE(m.lcRow,
loBmp.nHeight)
loBmp.genbmp("05")
DEFINE CLASS bmpcreator as Custom
* Generic
properties
nWidth = 1 &&
Bitmap width in pixels
nHeight = 1 &&
bitmap height in pixels
cBitmap = '' && the
bitmap as a string of RGB triplets
**************************************************************************************
*
generic procedure that writes the bitmap to a BMp file, stored in cBitmap
property
**************************************************************************************
PROCEDURE genbmp
*
*
Returns the name of the bmp file
*
*
Parameters:
*
- tcFile (optional) file name. By default sys(2015)
*
LPARAMETERS tcFile
LOCAL lni,lnByteLength,lcSa,lnNumber
IF PCOUNT() < 1
tcFile
= SYS(2015)
ENDIF
tcFile = FORCEEXT(m.tcFile,
'bmp')
lnByteLength
= LEN(This.cBitmap)
* Header
*
Bitmap header field: BM (CHR(0x42)+CHR(0x4D))
lcSa = CHR(0x42) + CHR(0x4D)
* File length
(file dimension in bytes in hexadecimal)
lnNumber = This.DecTohex(m.lnByteLength
+ 56)
lcSa
= m.lcSa + m.lnNumber
FOR lni = 1 TO 8 - LEN(m.lnNumber)
lcSa
= m.lcSa + CHR(0)
NEXT
*CHR(0x36)=3*16+6=56=header
length in bytes
*CHR(0x28)=2*16+8=40=number
of bytes taken by the structure that follows the header
lcSa = m.lcSa + CHR(0x36) + CHR(0) + CHR(0) + CHR(0) + CHR(0x28) + CHR(0) + CHR(0) + CHR(0)
* bitmap width
and height in pixels
*
bitmap width
lnNumber = This.DecTohex(This.nWidth) &&(lnByteLength/lnSize-2)/3
lcSa= m.lcSa +
m.lnNumber
FOR lni = 1 TO 4 - LEN(m.lnNumber)
lcSa
= m.lcSa + CHR(0)
NEXT
* bitmap height
lnNumber = This.DecTohex(This.nHeight)
lcSa
= m.lcSa + m.lnNumber && +CHR(0x0C)+CHR(0)+CHR(0)+CHR(0)
FOR lni = 1 TO 4 - LEN(m.lnNumber)
lcSa
= m.lcSa + CHR(0)
NEXT
* Number of
layers, must be 1
lcSa = m.lcSa + CHR(0x1) + CHR(0)
* Color depth:
1, 4, 8 sau 24 (0x18) bits
lcSa = m.lcSa + CHR(0x18) + CHR(0)
* Information
regarding compression
lcSa = m.lcSa + CHR(0) + CHR(0) + CHR(0) + CHR(0)
* Image length in bytes (can be 0 if is not
compressed)
lnNumber = This.DecTohex(m.lnByteLength)
lcSa
= m.lcSa + m.lnNumber
FOR lni = 1 TO 8 - LEN(m.lnNumber)
lcSa = m.lcSa + CHR(0)
NEXT
* the device
horizontal resolution in pixels
lcSa = m.lcSa + CHR(0) + CHR(0) + CHR(0) + CHR(0)
* the device
vertical resolution in pixels
lcSa = m.lcSa + CHR(0) + CHR(0) + CHR(0) + CHR(0)
* 0 means the
entire color set
lcSa = m.lcSa + CHR(0) + CHR(0)
* 0 means all
the color counts in bitmap representation
lcSa = m.lcSa + CHR(0) + CHR(0)
STRTOFILE(m.lcSa + This.cBitmap, m.tcFile)
RETURN m.tcFile
ENDPROC
* function used
to represend numbers as char
PROCEDURE DecTohex
LPARAMETERS tnNo
LOCAL lcS,lnC,lnI
lnI
= FLOOR(m.tnNo)
lcS
= ''
DO WHILE m.lnI != 0
lnC
= m.lnI % 256
lcS
= m.lcS + CHR(m.lnC)
lnI
= FLOOR(m.lnI / 256)
ENDDO
IF
LEN(m.lcS)=0
&&
representation of 0
lcS = CHR(0)
ENDIF
RETURN
m.lcS
ENDPROC
ENDDEFINE
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http://praisachion.blogspot.com/2017/09/creating-bitmap-bmp-pictures-without_45.html
http://praisachion.blogspot.com/2017/09/creating-bitmap-bmp-pictures-without_44.html
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