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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.  
[[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.


[Image:Forrest original.gif]
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]].


[Image:Forrest raster version.png]
''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 02:40, 17 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

Error creating thumbnail: Unable to save thumbnail to destination

Picture using rasters

Error creating thumbnail: Unable to save thumbnail to destination

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

If rasters provide improvement is up for debate at:

CPCWIKI forum entry

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