Assembly graphic couldn't display right colour from array - arrays

Question

Welcome.
I could't get values from 2d array. I am trying and trying and it doesn't work. I use NASM 16 DOS
I want to have blue letter E on red backgroung. I only get square random colours.
'1' in array is blue,'4' is red. It could be spinned, but it doesn't matter.
I have no idea what is wrong. I'm trying to do this a couple od days.
Here is my code:
segment .data
segment .code
..start:
mov ax, 13h
int 10h ; switch to 320x200 mode
mov ax, 0a000h ; The offset to video memory
mov es, ax ; We load it to ES through AX,
; because immediate operation
; is not allowed on ES
;;;;;;;;;;;;;;;;;;;;;;
mov si, T34 ; my array
mov word [Y_Start], 10 ; Y start line count values in register
mov word [X_Start], 20 ; X start line
mov word [Y], 10 ; Y start line
mov word [X], 20 ; X start line
mov dx, 4 ; colour (red)
mov cx, 8 ; loop top counter
top:
add word [Y], 1
push cx ;loop top counter =
mov cx, 8 ;inside loop counter
inside:
add word [X], 1
;////////////////////////////////////////////// count colour
push ax ; remember value before procedure
push bx
push cx
push dx
mov ax, word [X]
mov cx,8
mul cx ;X*8
add ax, word[Y] ; X*8 +Y
mov cx,4
mul cx ; (X*8+Y)*4
add ax, si ; tab0 + (X*8+Y)*4
pop dx
mov dx, ax; colour
pop cx
pop bx
pop ax
;///////////////////////////////////////////
mov ax, word [Y]
mov bx, word [X]
push ax ; remember value before procedure
push bx
push cx
call putpixel
pop cx ; go back to old values
pop bx
pop ax
loop inside
mov bx, word [X_Start] ; move to X start
mov word [X], bx ;
pop cx ;loop top counter
loop top
;;;;;;;;;;;;;;;;;;;;;;;;;
xor ah, ah
int 16h ; keyboard (wait for key)
mov ax, 3
int 10h ; go to text mode
mov ax, 4c00h
int 21h ; return to DOS, exit code 0
;;;;;;;;;;;;;;;;;;;;;
putpixel:
push dx ; mul changes dx too
mov cx, 320
mul cx ; multiply Y (ax) by 320 (one row)
add ax, bx ; and add X (bx) (result= dx:ax)
mov di, ax
pop dx
mov [es:di], dx ; store color/pixel
ret
;;;;;;;;;;;;;;;;;;;;;;
X_Start DW 0 ; start letter position
Y_Start DW 0
X DW 0 ;current letter position
Y DW 0
T34 DB 1,1,1,1,1,1,1,1
DB 1,4,4,4,4,4,4,4
DB 1,4,4,4,4,4,4,4
DB 1,4,4,4,4,4,4,4
DB 1,1,1,1,1,1,1,1
DB 1,4,4,4,4,4,4,4
DB 1,4,4,4,4,4,4,4
DB 1,1,1,1,1,1,1,1

Answer 1

I didn't catch your approach, but I can show you how I would do it:
segment .code
..start:
mov ax, data ; Initialize DS (needed for .exe-program)
mov ds, ax
mov ax, 0A000h ; Segment to video memory
mov es, ax
mov ax, 13h
int 10h ; Switch to 320x200 mode
mov si, T34 ; DS:SI = letter
mov bx, [X_Start]
mov ax, [Y_Start]
call vector_to_memory
mov di, ax ; ES:DI = video memory
call paint
; once more
add word [X_Start], 8 ; That's one small step for a man
mov si, T34 ; DS:SI = letter
mov bx, [X_Start]
mov ax, [Y_Start]
call vector_to_memory
mov di, ax ; ES:DI = video memory
call paint
xor ah, ah
int 16h ; keyboard (wait for key)
mov ax, 3
int 10h ; go to text mode
mov ax, 4c00h
int 21h ; return to DOS, exit code 0
paint: ; Args: DS:SI = letter, ES:DI: video memory
mov ax, 8
.l1:
mov cx, 8 ; repetition count for REP
rep movsb ; CX times (one row): [DS:SI] => [ES:DI], SI++, DI++
add di, (320-8) ; next row
sub ax, 1 ; no row left?
jnz .l1 ; no: once more
ret ; yes: paint is done, return
vector_to_memory: ; Args: BX = X, AX = Y
push dx ; mul changes dx too
mov cx, 320 ; video mode width
mul cx ; DX:AX = AX * CX
add ax, bx ; left indentation
pop dx
ret ; Return: AX = offset in memory
segment .data
T34:
DB 1,1,1,1,1,1,1,1
DB 1,4,4,4,4,4,4,4
DB 1,4,4,4,4,4,4,4
DB 1,4,4,4,4,4,4,4
DB 1,1,1,1,1,1,1,1
DB 1,4,4,4,4,4,4,4
DB 1,4,4,4,4,4,4,4
DB 1,1,1,1,1,1,1,1
X_Start DW 10 ; start letter position
Y_Start DW 20
segment stack stack
resb 0x1000
HTH

Answer 2

You're not loading the pixel values correctly:
add ax, si ; tab0 + (X*8+Y)*4
mov dx, ax; colour <-- Here you're just copying the _address_, you're
not loading the value stored at that address.
Those two instructions should be changed to:
add si,ax
mov dl,[si]
Note the use of dl since you're dealing with bytes. I also switched the add around because [ax] wouldn't be a valid effective address. This means that you'll have to reload si with the address of the array on every iteration of the loop.
The line mov [es:di], dx in putpixel should also be changed to mov [es:di], dl.
Some of your multiplications could be simplified: to multiply a register by 4 you can do shl reg,2, and to multiply by 8 you can do shl reg,3.