Gray sky
(C) Shaitan / Stars of Keladan
This is precisely the color you would see the sky,
if people did not have a color analyzer eyes. In my opinion I
drive. Well, here suggest vyshemu attention
description of algorithm translation of color
_Spekrumovskogo_ Image gradation
gray. You might ask: "Why
is Spectrum? "And everything is very
simple - because Spekruma special
construction of the screen, and the algorithm is to
and this is based. But if you understand the case, then such
feature can be implemented to any platform, but it's not a fact.
So, let's begin.
First we need to decide how many shades of gray would be
consistent Our flowers and build a table of 8
(16), texture units in the following format. First
are 8 bytes of zero color, then 8 bytes
the second and so on until the 8 th or 16 th. In
example shows the files of that
uses 8 levels of gray, from black
to white, including, but not attaching
much effort it can be easily peredalat
at 16, that is, taking into account the brightness of the flag.
Such an algorithm, and the procedure is used in the module Grey
Scale Convertor versions 1.0 and 2.0 for rulezneyshego graphics
editor BGE. And now we have to listen to me very
carefully, so as to be beyond
description of the algorithm.
I hope that you are familiar with
structure of the Spectrum screen and
you is not news that we are so we have 8 colors + 2 graduation
brightness of each, a total of 16 colors of ink and 16 in the
background, and generally get 256 color combinations on
familiarity. The algorithm I will show you
in the following graphic area, which the ink is green, and the
background red.
For convenience, the digestion of my ravings
except for the image in full size
bring the image in an eightfold
magnification.
So true. Read the attribute
appropriate familiarity and it
determine the numbers and start addresses
textures for the background and ink. Then read the first byte
of familiarity to remember on the stack and put on a mask byte
first byte of ink. The resulting bytes be gdenibud remember it
for later recovery. Now remove from the stack byte value
familiarity, invert him and put on his mask as the first byte,
but the background. Now, as the opofigey, we must add to both
OR'u masked-byte, and then we received bytes to put in place
the original byte. After all of the these actions we can proceed
by the second byte of familiarity, only
it is not necessary to determine the address of textures and
as a mask byte must use the second byte of the same texture.
After we walked around
familiarity, we need him to put the attribute you want with the
code # 38, that is background to white, and black ink and
it all off with brilliance. As a result, you have something like
(See color example).
We can then proceed to
next familiarity, and all actions necessary to produce again.
To better understand the quote you the original procedure of
translation in shades of gray, which was used in the module
with version 1.0 of BGE.
SCREEN EQU # 4000
ATTR EQU # 5800
LD HL, SCREEN
LD DE, ATTR
LD B, 24; lines in screen
M3 PUSH BC
PUSH HL
LINFIL LD B, 32; familiarity in a row
M2 PUSH BC
LD A, (DE)
PUSH HL
PUSH DE
PUSH AF
RRA; determine the address of the background texture
RRA
RRA
LD DE, ATR_TBL
AND 7
ADD A, A
ADD A, A
ADD A, A
LD H, 0
LD L, A
ADD HL, DE
LD (PAP), HL
POP AF
AND 7, determines the address of the inky texture
ADD A, A
ADD A, A
ADD A, A
LD H, 0
LD L, A
ADD HL, DE
LD (INK), HL
POP DE
POP HL
PUSH HL
LD B, 8; the number of bytes in the familiarity
M1 LD A, (HL); read bytes from familiarity
PUSH HL
PUSH AF
LD HL, (INK)
AND (HL); put ink mask
LD C, A; remember
INC HL
LD (INK), HL
LD HL, (PAP)
POP AF
CPL; invert the original bytes
AND (HL); put a background mask
OR C; connects two bytes received
INC HL
LD (PAP), HL
POP HL
LD (HL), A; put in place
CALL DOWN_HL; Come over to the underlying byte
DJNZ M1
LD A, # 38, put the attribute
LD (DE), A
POP HL
INC HL
INC DE
POP BC; proceed to the next
; Familiarity
DJNZ M2
POP HL
CALL LOWERHL
POP BC; disguised to the next line
DJNZ M3
RET
DOWN_HL INC H
LD A, H
AND 7
RET NZ
LD L, A
ADD A, # 20
LD L, A
RET C
LD A, H
SUB 8
LD H, A
RET
LOWERHL LD A, L
ADD A, # 20
LD L, A
RET NC
LD A, H
ADD A, 8
LD H, A
RET
ATR_TBL; but it ourselves texture
DEFB # FF, # FF, # FF, # FF;-BLACK
DEFB # FF, # FF, # FF, # FF
DEFB # 77, # FF, # DD, # FF;-BLUE
DEFB # 77, # FF, # DD, # FF
DEFB # AA, # FF, # AA, # FF;-RED
DEFB # AA, # FF, # AA, # FF
DEFB # 55, # BB, # 55, # EE;-MAGENTA
DEFB # 55, # BB, # 55, # EE
DEFB # 55, # AA, # 55, # AA;-GREEN
DEFB # 55, # AA, # 55, # AA
DEFB # 55, # 22, # 55, # 88;-CYAN
DEFB # 55, # 22, # 55, # 88
DEFB # 55, # 00, # 55, # 00;-YELLOW
DEFB # 55, # 00, # 55, # 00
DEFB # 00, # 00, # 00, # 00;-WHITE
DEFB # 00, # 00, # 00, # 00
INK DEFW # 0000
PAP DEFW # 0000
6 In the appendix can we meet this source in the format Alasm,
but without comment. But what can be achieved by
This protsedurki.
