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101 lines
2.1 KiB
NASM
101 lines
2.1 KiB
NASM
6 years ago
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%ifndef CODE_BUFFER
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%define CODE_BUFFER
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;set's graphic mode
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initGraphics:
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mov ah, 0 ;set display mode
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mov al, 13h ;13h = 320x200
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int 0x10
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ret
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;resets screen to full black
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resetBuffer:
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pusha
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mov cx, 80*60/2
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;xor ax, ax ;this will make the background black
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mov ax, 0xC3C3 ;this paints the background green
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mov di, [screenPos]
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rep stosw
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popa
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ret
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;screen has size 320x200 but buffer only 80x60
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copyBufferOver:
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pusha
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push es
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mov es, word [graphicMemory]
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xor di, di
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mov cx, 200
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.loop:
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mov dx, cx
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mov cx, 320/4
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.innerloop:
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mov si, 320
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sub si, cx ;invert x-axis
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mov bx, 200
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sub bx, dx ;invert y-axis
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shr bx, 2
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imul bx, 80
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add si, bx
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add si, [screenPos]
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lodsb ;read from buffer (ds:si)
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mov ah, al
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stosw ;write 4 pixel row to graphic memory (es:di)
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stosw
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loop .innerloop
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mov cx, dx
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loop .loop
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pop es
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popa
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ret
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;si = position of image, ax = xpos, bx = ypos
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;a bit messy because of all the error checks to not draw out of screen
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drawImage:
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pusha
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xor di, di
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imul di, bx, 80 ;add offset y-position
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add di, [screenPos] ;make it a pixel in buffer
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;add di, ax ;add offset x-position
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mov bp, ax ;backup x-position offset
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xor ax, ax
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lodsb
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mov cx, ax ;x-size
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lodsb
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mov dx, ax ;y-size
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.for_y:
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mov bx, di
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add bx, cx ;bx = offsetOnScreen + xsize
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sub bx, word [screenPos] ;skip if line is out of top border screen
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jl .skip_x
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sub bx, cx
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sub bx, 80*60
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jge .skip_x ;skip if line is out of bottom border screen
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xor bx, bx
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.for_x:
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mov al, byte [si+bx]
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add bx, bp
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test al, al ;skip 0bytes as transparent
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jz .skip
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cmp bx, 80 ;if pixel is right out of screen, skip it
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jge .skip
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cmp bx, 0 ;if pixel is left out of screen, skip it
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jl .skip
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mov byte [di+bx], al ;write byte to buffer
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.skip:
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sub bx, bp
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inc bx
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cmp bx, cx
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jl .for_x
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.skip_x:
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add di, 80 ;next row within buffer
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add si, cx ;next row within image
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dec dx
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jnz .for_y ;repeat for y-length
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popa
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ret
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graphicMemory dw 0xA000
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screenPos dw 0x0500 ;double buffer will be at this address
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%endif
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