Difference between revisions of "Forrest picture"

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'''Forrest Picture''' is a demonstration on how to use the graphic abilities of the CPC. The picture uses [[mode 1]] of the CPC. The graphic mode is limited to 4 simultanious colors.  
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[[Category:Graphic]]
 +
'''Forrest Picture''' is a picture drawn by [[Mr. Lou]]s girlfriend, and is a demonstration on how to use the graphic abilities of the CPC.
  
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[[Image:Forrest original.gif]]
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The picture uses [[Video modes|mode 1]] of the CPC. The graphic mode is limited to 4 simultanious colors. After publication the picture became the subject on how to break the 4 colour limit in mode 1 using [[rasters]]. Subsequent [[Tom & Jerry of GPA|T&J]] wrote a small program showing how the picture would look like using rasters generated by the [[Gate Array|gate array]].
  
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[[Image:Forrest raster version.png]]
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''Original picture''
 +
 
 +
[[Image:Forrest picture.png|320px|Picture drawn by Mr. Lous girlfriend]]
 +
 
 +
''Picture using rasters''
 +
 
 +
[[Image:Forrest raster version.png|320px|Picture using raster routine by T&J]]
 +
 
 +
== Sourcecode ==
 +
 
 +
<geshi lang=z80>
 +
; Example of rasters in a MODE 1 screen
 +
; T&J/GPA in 2009
 +
 
 +
; Done under WINAPE
 +
; Not tested on a real CPC, so maybe it needs some timing adjustments
 +
 
 +
; Wait for Color Lines ! Rasters inside !!
 +
 
 +
ORG &9000
 +
NOLIST
 +
WRITE "RASTERS.BIN"
 +
 
 +
black equ &54
 +
grey equ &41
 +
green_19 equ &51
 +
red_6 equ &4C
 +
blue_1 equ &44
 +
blue_11 equ &57
 +
blue_14 equ &5F
 +
bleu_clair equ &53
 +
 
 +
violet equ &58
 +
 
 +
JP booter
 +
 
 +
save38 defw &0
 +
 
 +
Booter DI
 +
LD HL,(&38)
 +
LD (save38),HL
 +
LD HL,&C9FB
 +
LD (&38),HL
 +
EI
 +
 
 +
 
 +
main DI
 +
LD B,&F5
 +
sync IN A,(C)
 +
RRA
 +
JR NC,sync
 +
 
 +
CALL scan_spacekey
 +
CP &7F
 +
JP Z,endit
 +
 
 +
LD BC,&7F02    ; sky
 +
OUT (C),C
 +
LD A,blue_11
 +
OUT (C),A
 +
 
 +
EI
 +
 
 +
HALT
 +
 
 +
HALT
 +
 
 +
LD HL,&FDD0
 +
wait1 INC HL
 +
LD A,H
 +
AND A
 +
JR NZ,wait1
 +
 
 +
LD BC,&7F02
 +
OUT (C),C
 +
LD A,&5F
 +
OUT (C),A
 +
 
 +
HALT
 +
HALT
 +
 
 +
LD HL,&FFC0
 +
wait2 INC HL
 +
LD A,H
 +
AND A
 +
JR NZ,wait2
 +
 
 +
LD BC,&7F02 ; board of the lake
 +
OUT (C),C
 +
LD A,grey
 +
OUT (C),A
 +
 
 +
LD HL,&FF74
 +
wait3 INC HL
 +
LD A,H
 +
AND A
 +
JR NZ,wait3
 +
 
 +
LD BC,&7F02
 +
OUT (C),C
 +
 
 +
LD D,green_19
 +
LD E,red_6
 +
 
 +
DI
 +
 
 +
LD A,&40
 +
 +
split1 OUT (C),E  ; red mushrooms
 +
PUSH AF
 +
NOP
 +
NOP
 +
NOP
 +
NOP
 +
NOP
 +
OUT (C),D  ; green mushroom
 +
 
 +
NOP
 +
NOP
 +
NOP
 +
 
 +
LD A,&9
 +
waitsp1 DEC A
 +
JR NZ,waitsp1
 +
 
 +
POP AF
 +
DEC A
 +
JR NZ,split1
 +
 
 +
JP main
 +
 
 +
endit
 +
 
 +
LD BC,&7F02    ; sky
 +
OUT (C),C
 +
LD A,blue_14
 +
OUT (C),A
 +
 
 +
LD HL,(save38)
 +
DI
 +
LD (&38),HL
 +
EI
 +
RET
 +
 
 +
scan_spacekey
 +
 
 +
LD BC,&F40E
 +
OUT (C),C
 +
LD BC,&F6C0
 +
OUT (C),C
 +
LD C,&0
 +
OUT (C),C
 +
LD BC,&F792
 +
OUT (C),C
 +
LD BC,&F645
 +
OUT (C),C
 +
LD B,&F4
 +
IN A,(C)
 +
LD BC,&F782
 +
OUT (C),C
 +
LD BC,&F600
 +
OUT (C),C
 +
RET
 +
</geshi>
 +
 
 +
== Download ==
 +
 
 +
[[Media:trees.DSK|DSK image with picture and source code]]
 +
 
 +
== Links ==
 +
 
 +
If rasters provide improvement is up for debate at:
 +
 
 +
[http://cpcwiki.eu/forum/index.php/topic,396.msg3146.html#msg3146 CPCWIKI forum entry]

Latest revision as of 21:40, 16 December 2010

Forrest Picture is a picture drawn by Mr. Lous girlfriend, and is a demonstration on how to use the graphic abilities of the CPC.

The picture uses mode 1 of the CPC. The graphic mode is limited to 4 simultanious colors. After publication the picture became the subject on how to break the 4 colour limit in mode 1 using rasters. Subsequent T&J wrote a small program showing how the picture would look like using rasters generated by the gate array.

Original picture

Picture drawn by Mr. Lous girlfriend

Picture using rasters

Picture using raster routine by T&J

Sourcecode

<geshi lang=z80>

Example of rasters in a MODE 1 screen
T&J/GPA in 2009
Done under WINAPE
Not tested on a real CPC, so maybe it needs some timing adjustments
Wait for Color Lines ! Rasters inside !!

ORG &9000 NOLIST WRITE "RASTERS.BIN"

black equ &54 grey equ &41 green_19 equ &51 red_6 equ &4C blue_1 equ &44 blue_11 equ &57 blue_14 equ &5F bleu_clair equ &53

violet equ &58

JP booter

save38 defw &0

Booter DI LD HL,(&38) LD (save38),HL LD HL,&C9FB LD (&38),HL EI


main DI LD B,&F5 sync IN A,(C) RRA JR NC,sync

CALL scan_spacekey CP &7F JP Z,endit

LD BC,&7F02  ; sky OUT (C),C LD A,blue_11 OUT (C),A

EI

HALT

HALT

LD HL,&FDD0 wait1 INC HL LD A,H AND A JR NZ,wait1

LD BC,&7F02 OUT (C),C LD A,&5F OUT (C),A

HALT HALT

LD HL,&FFC0 wait2 INC HL LD A,H AND A JR NZ,wait2

LD BC,&7F02 ; board of the lake OUT (C),C LD A,grey OUT (C),A

LD HL,&FF74 wait3 INC HL LD A,H AND A JR NZ,wait3

LD BC,&7F02 OUT (C),C

LD D,green_19 LD E,red_6

DI

LD A,&40

split1 OUT (C),E  ; red mushrooms PUSH AF NOP NOP NOP NOP NOP OUT (C),D  ; green mushroom

NOP NOP NOP

LD A,&9 waitsp1 DEC A JR NZ,waitsp1

POP AF DEC A JR NZ,split1

JP main

endit

LD BC,&7F02  ; sky OUT (C),C LD A,blue_14 OUT (C),A

LD HL,(save38) DI LD (&38),HL EI RET

scan_spacekey

LD BC,&F40E OUT (C),C LD BC,&F6C0 OUT (C),C LD C,&0 OUT (C),C LD BC,&F792 OUT (C),C LD BC,&F645 OUT (C),C LD B,&F4 IN A,(C) LD BC,&F782 OUT (C),C LD BC,&F600 OUT (C),C RET </geshi>

Download

DSK image with picture and source code

Links

If rasters provide improvement is up for debate at:

CPCWIKI forum entry

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