Re: What am I doing wrong here? Trying to draw 10 lines, multiple colors
- From: "Wolfgang Kern" <nowhere@xxxxxxxx>
- Date: Tue, 26 Feb 2008 10:19:05 +0100
"nobody" <mojo0716> asked:
What am I doing wrong here? Trying to draw 10 lines, multiple colors
I got the 10 lines, but I can't get multiple colors working. What am I
doing wrong?
You add rgb values 10 times, the palette register uses only 6/8 bits ...
but even it will rollover it should show some change.
*** The palette register change (3C8/3C9) may not take effect until
the next screen refresh ?
How if you insert a delay or wait for retrace ?
You can define up to 256 individual colours in a loop by using
the auto-increment feature of the palette register set.
I'd define several (if not all) colours ahead of the draw-loop
and use for test ie: the low byte of loop count as 'colour index'.
This would make the draw faster and with a few modifications it
also let you direct draw bitmaps.
__
wolfgang
; Memory Mapped Graphics, Mode 13 (Mode13.asm)
Comment !
This program demonstrates direct memory mapping in video
graphics Mode 13 (320 x 200, 256 colors). The video memory
is a two-dimensional array of memory bytes which can be addressed
and modified individually. Each byte represents a pixel on
the screen, and each byte contains an index into the color
palette.
Last update: 06/01/2006
!
INCLUDE Irvine16.inc
VIDEO_PALLETE_PORT = 3C8h
COLOR_SELECTION_PORT = 3C9h
COLOR_INDEX = 1
PALLETE_INDEX_BACKGROUND = 0
SET_VIDEO_MODE = 0
GET_VIDEO_MODE = 0Fh
VIDE0_SEGMENT = 0A000h
WAIT_FOR_KEYSTROKE = 10h
MODE_13 = 13h
.data
saveMode BYTE ? ; saved video mode
xVal WORD ? ; x-coordinate
yVal WORD ? ; y-coordinate
msg BYTE "Welcome to Mode 13!",0
redValue BYTE 0
greenValue BYTE 0
blueValue BYTE 0
loopCount WORD ?
addToX WORD 0
.code
main PROC
mov ax,@data
mov ds,ax
call SetVideoMode
call SetScreenBackground
; Display a greeting message.
mov edx,OFFSET msg ; DOS calls work also
call WriteString
mov cx,10
MULTIPLELINES:
add addToX,30
mov loopCount,cx
call Draw_Some_Pixels
mov cx,loopCount
add redValue,20
add greenValue,60
add blueValue,50
loop MULTIPLELINES
call RestoreVideoMode
exit
main ENDP
;------------------------------------------------
SetScreenBackground PROC
;
; Sets the screen's background color. Video
; palette index 0 is the background color.
;------------------------------------------------
mov dx,VIDEO_PALLETE_PORT
mov al,PALLETE_INDEX_BACKGROUND
out dx,al
; Set the screen background color to dark blue.
mov dx,COLOR_SELECTION_PORT
mov al,0 ; red
out dx,al
mov al,0 ; green
out dx,al
mov al,35 ; blue (intensity 35/63)
out dx,al
ret
SetScreenBackground endp
;-----------------------------------------------
SetVideoMode PROC
;
; Saves the current video mode, switches to a
; new mode, and points ES to the video segment.
;-----------------------------------------------
mov ah,GET_VIDEO_MODE
int 10h
mov saveMode,al ; save it
mov ah,SET_VIDEO_MODE
mov al,MODE_13 ; to mode 13h
int 10h
push VIDE0_SEGMENT ; video segment address
pop es ; ES points to video segment
ret
SetVideoMode ENDP
;---------------------------------------------
RestoreVideoMode PROC
;
; Waits for a key to be pressed and restores
; the video mode to its original value.
;----------------------------------------------
mov ah,WAIT_FOR_KEYSTROKE
int 16h
mov ah,SET_VIDEO_MODE ; reset video mode
mov al,saveMode ; to saved mode
int 10h
ret
RestoreVideoMode ENDP
;-----------------------------------------------
Draw_Some_Pixels PROC
;
; Sets individual palette colors and draws
; several pixels.
;------------------------------------------------
.code
; Change the color at index 1 to white (63,53,43).
mov dx,VIDEO_PALLETE_PORT
mov al,1 ; set palette index 1
out dx,al
mov dx,COLOR_SELECTION_PORT
mov al,redValue ; red
out dx,al
mov al,greenValue ; green
out dx,al
mov al,blueValue ; blue
out dx,al
; Calculate the video buffer offset of the first pixel.
; Method is specific to mode 13h, which is 320 X 200.
mov xVal,0 ; middle of screen
mov ax,addToX
add xVal,ax
mov yVal,20
mov ax,320 ; 320 for video mode 13h
mul yVal ; y-coordinate
add ax,xVAl ; x-coordinate
; Place the color index into the video buffer.
mov cx,150 ; draw 10 pixels
mov di,ax ; AX contains buffer offset
; Draw the pixels now. By default, the assembler assumes
; DI is an offset from the segment address in DS. The
; segment override ES:[DI] tells the CPU to use the segment
; address in ES instead. ES currently points to VRAM.
DP1:
mov BYTE PTR es:[di],COLOR_INDEX
add di,320 ;move 5 pixels to the right
;add di,5
loop DP1
ret
Draw_Some_Pixels ENDP
END main
.
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