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calc_offs MACRO xval,yval

	mov bx,xval
	mov ax,yval

  	xchg	ah,al			; ax=256*y
  	add	bx,ax			; bx=256*y+x
  	shr	ax,2
  	add	bx,ax			; bx=320*y+x (+ offset in buffer if needed.)

	ENDM


img_cpy	MACRO wdth,hght,src_seg,src_offs,dest_seg,dest_offs
	LOCAL y_lp, x_lp, skip_palreg0,w_hor

	mov dx,wdth
	mov bx,hght

	mov bp,320
	sub bp,wdth

	mov cx,0

	mov es,dest_seg
	mov di,dest_offs
	push ds
	mov si,src_offs
	mov ds,src_seg

y_lp:	mov ax,dx
x_lp:	mov cl,ds:[si]
	jcxz skip_palreg0
	mov es:[di],cl
skip_palreg0:
	inc si
	inc di
	dec ax
	jnz x_lp
	add si,bp			    ;next line
	add di,bp
	dec bx
	jnz y_lp

	pop ds

	ENDM

img_cpy2 MACRO wdth,hght,src_seg,src_offs,dest_seg,dest_offs
	 LOCAL y_rlp,div4_ok,min_ok

	mov bx,hght
	mov dx,wdth

	cmp dx,4
	jae min_ok
	mov dx,4
	jmp div4_ok
min_ok: test dx,0000000000000011b
	jz div4_ok
	add dx,3
	and dx,1111111111111100b
div4_ok:
	mov ax,320
	sub ax,dx
	shr dx,2

	mov es,dest_seg
	mov di,dest_offs
	push ds
	mov si,src_offs
	mov ds,src_seg

y_rlp:	mov cx,dx
	rep movsd
	add si,ax
	add di,ax
	dec bx
	jnz y_rlp

	pop ds

	ENDM


img_rest MACRO wdth,hght,src_seg,src_offs,dest_seg,dest_offs
	LOCAL y_rlp,min_ok,div4_ok

	mov bx,hght
	mov dx,wdth

	cmp dx,4
	jae min_ok
	mov dx,4
	jmp div4_ok
min_ok: test dx,0000000000000011b
	jz div4_ok
	add dx,3
	and dx,1111111111111100b
div4_ok:
	mov ax,320
	sub ax,dx
	shr dx,2

	mov es,dest_seg
	mov di,dest_offs
	push ds
	mov si,src_offs
	mov ds,src_seg


y_rlp:	mov cx,dx
	rep movsd
	add si,ax
	add di,ax
	dec bx
	jnz y_rlp

	pop ds

	ENDM
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