wu'ed in haste; fried, stewed at leisure

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mov es.ax :point ES:DI to next pixel to drawmov al.byte ptr [bp].BaseColor :color with which to draw:CX - DeltaX at this pointrep stosb :draw the rest of the horizontal linecl d :restore default direction fjmp Done ;and we're donealign 2NotHorz:and cx.cxjnz NotVertmov a1 .byte ptr [bp].BaseColorVert Loop :add si.SCREEN-WIDTH-IN-BYTESmov [sil.aldec dxjnz VertLoopjmp Done:is DeltaX O?:no, not a vertical line:yes. is vertical, special case;color with which to draw:point to next pixel to draw:draw the next pixel: --Del taY:and we're donealign 2NotVert :cmp cx,dx ;DeltaX - DeltaY?jnz NotDiag :no, not diagonal:yes. is diagonal, special casemov a1,byte ptr [bpl.BaseColor ;color with which to drawDiagLoop:lea si .[si+SCREEN-WIDTH-IN-BYTES+bx];advance to next pixel to draw by; incrementing Y and adding XDir to Xmov [si 1 .a1 :draw the next pixeldec dx :--Del taYjnz DiagLoopjmp Done ;and we're done: Line is not horizontal, diagonal, or vertical.align 2NotDiag:: Is this an X-major or Y-major line?cmp dx.cxjb XMajor :it's X-major: It's a Y-major line. Calculate the 16-bit fixed-point fractional part of a: pixel that X advances each time Y advances 1 pixel, truncating the result: to avoid overrunning the endpoint along the X axis.xchg dx.cx :DX - DeltaX. CX - DeltaYsub ax.ax ;make DeltaX 16.16 fixed-point value DX:AX indiv cx ;AX - (DeltaX
mov cx.8 :CL - # of bits by which to shiftsub cx.Cbpl.1ntensityBits : ErrorAcc to get intensity (8 level: instead of 16 because we work only: with the high byte of ErrorAcc)mov ch.byte ptr [bpl.NumLevels ;mask used to flip all bits an indec ch : intensity , weightingproducing: result (1 - intensity weighting)mov bp.BaseColor[bp] :***stack frame not available***;***from now on ***xchg bp.ax ;BP - ErrorAdj. AL - BaseColor.: AH - scratch register: Draw all remaining pixels.YMajorLoop:add dx.bp :calculate error for next pixeljnc NoXAdvance :not time to step in X yet:the error accumulator turned over,;so advance the X coordadd si .bx :add XDir to the pixel pointerNoXAdvance:add si.SCREEN-WIDTH-IN-BYTES ;Y-major, so always advance Y; The IntensityBits most significant bits of ErrorAcc give us the intensity; weighting for this pixel. and the complement of the weighting for the: paired pixel.mov ah.dh :msb of ErrorAccshr ah.cl :Weighting - ErrorAcc >> IntensityShift:add ah.al : BaseCol or + Weightingmov [si 1 ,ah :DrawPixel(X. Y. BaseColor + Weighting):mov ah.dh :msb of ErrorAccshr ah.cl :Weighting - ErrorAcc >> IntensityShift:xor ah.ch :Weighting A WeightingComplementMaskadd ah.al :BaseColor + (Weighting A WeightingComplementMask)mov [si+bx] ,ah :DrawPixel(X+XDir. Y.: BaseColor + (Weighting A WeightingComplementMask));dec di :--Del taYjnz YMajorLoopjmp Done :we're done with this line: It's an X-major line.align 2XMajor:: Calculate the 16-bit fixed-point fractional part of a pixel that Y advances: each time X advances 1 pixel, truncating the result to avoid overrunning: the endpoint along the X axis.sub ax.ax :make DeltaY 16.16 fixed-point DX:AX value in790 Chapter 42div cx :AX - (DeltaY
Page 1: chapter 42wu'ed in haste; fried, st
Page 4 and 5: has the same brightness it would ha
Page 9 and 10: Sample Wu AntialiasingThe true test
Page 11 and 12: 1for (i-0; i
Page 13 and 14: Listing 42.1 isn’t particularly f
Page 15: .modelsmall.code; Screen dimension
Page 19: design a more accurate polygon-anti

wu'ed in haste; fried, stewed at leisure

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