+++ /dev/null
-;-----------------------------------------------------------\r
-;\r
-; MXEL.ASM - Mid-point ellipse\r
-; Copyright (c) 1994 by Alessandro Scotti\r
-;\r
-;-----------------------------------------------------------\r
-WARN PRO\r
-NOWARN RES\r
-INCLUDE MODEX.DEF\r
-\r
-PUBLIC mxEllipse\r
-\r
-MX_TEXT SEGMENT USE16 PARA PUBLIC 'CODE'\r
- ASSUME cs:MX_TEXT, ds:NOTHING, es:NOTHING\r
-\r
-EXTRN mx_BytesPerLine : WORD\r
-EXTRN mx_VideoSegment : WORD\r
-EXTRN mx_ClipX1 : WORD\r
-EXTRN mx_ClipY1 : WORD\r
-EXTRN mx_ClipX2 : WORD\r
-EXTRN mx_ClipY2 : WORD\r
-\r
-;-----------------------------------------------------------\r
-;\r
-; Draws an ellipse using the mid-point algorithm.\r
-;\r
-; Input:\r
-; XC, YC = center coordinates\r
-; A = horizontal radius\r
-; B = vertical radius\r
-; Color = ellipse color\r
-; Output:\r
-; none\r
-; Note:\r
-; computes only points in the first quadrant, all other\r
-; points are obtained by symmetry.\r
-;\r
-mxEllipse PROC FAR\r
- ARG Color:BYTE:2, \\r
- B:WORD, \\r
- A:WORD, \\r
- YC:WORD, \\r
- XC:WORD = ARG_SIZE\r
- LOCAL A2:DWORD, \\r
- B2:DWORD, \\r
- CC:DWORD, \\r
- DD:DWORD, \\r
- X:DWORD, \\r
- Y:DWORD = AUTO_SIZE\r
- .enter AUTO_SIZE\r
- .push ds, si, di\r
-\r
- .chk386 mxEllipse, @@Exit\r
-\r
-; Initialize variables\r
- xor eax, eax\r
- mov [X], ax ; X = 0\r
- mov ax, [A]\r
- mul eax ; EAX = A*A\r
- mov [DD], eax ; DD = A*A\r
- shl eax, 1\r
- mov [CC], eax ; CC = 2*A*A\r
- shl eax, 1\r
- mov [A2], eax ; A2 = 4*A*A\r
- movzx edx, [B]\r
- mov [Y], edx\r
- mul edx ; EAX = 4*A*A*B\r
- sub [DD], eax ; DD = A*A - 4*A*A*B\r
- movzx eax, [B]\r
- mul eax ; EAX = B*B\r
- shl eax, 2 ; EAX = 4*B*B\r
- mov [B2], eax ; B2 = 4*B*B\r
- add [CC], eax ; CC = 2*A*A + 4*B*B\r
- add [D1], eax ; DD = A*A - 4*A*A*B + 4*B*B\r
-\r
-; Draw initial points\r
- call subPlot4\r
-\r
-; First loop\r
-@@Loop1:\r
- mov eax, [X] ; Check slope\r
- mul [B2]\r
- mov ecx, eax\r
- mov eax, [Y]\r
- mul [A2]\r
- sub eax, ecx\r
- sub eax, [CC] ; EAX = Y*A2 - X*B2 - CC\r
- jle @@Done1 ; Crossed critical point, jump to next loop\r
-\r
- mov ecx, [DD] ; Get error\r
- test ecx, ecx ; Positive?\r
- jl @@Draw1 ; No, use default step\r
-\r
- mov eax, 1\r
- sub eax, [Y]\r
- mul [A2]\r
- shl eax, 1\r
- add ecx, eax ; Bump error\r
- dec WORD PTR [Y] ; Decrement Y coordinate\r
-\r
-@@Draw1:\r
- mov eax, [X]\r
- shl eax, 1\r
- add eax, 3\r
- mul [B2]\r
- add ecx, eax ; Bump error\r
- mov [DD], ecx ; Save error\r
- inc WORD PTR [X] ; Increment X coordinate\r
-\r
- call subPlot4 ; Draw points\r
- jmp @@Loop1\r
-@@Done1:\r
-\r
-; Initialize variables\r
- shr [B2], 2\r
- mov eax, [X]\r
- mul eax\r
- add [X]\r
- shl eax, 2\r
- inc eax\r
- mul [B2]\r
- mov [DD], eax\r
- mov eax, [Y]\r
- mul eax\r
- add [Y]\r
- dec eax\r
- add [Y]\r
- sub eax, [B2]\r
- add [DD], eax\r
- shl [B2], 3\r
- inc WORD PTR [X]\r
-\r
-; Second loop\r
-@@Loop2:\r
- cmp WORD PTR [Y], 0\r
- ja @@Done2\r
-\r
- mov ecx, [DD]\r
- test ecx, ecx\r
- jge @@Draw2\r
-\r
- mov eax, [X]\r
- inc eax\r
- mul [B2]\r
- add ecx, eax\r
- inc WORD PTR [X]\r
-\r
-@@Draw2:\r
- mov eax, [Y]\r
- shl eax, 1\r
- sub eax, 3\r
- neg eax\r
- imul [A2]\r
- add ecx, eax\r
- dec WORD PTR [Y]\r
-\r
- call subPlot4\r
- jmp @@Loop2\r
-@@Done2:\r
-\r
-@@Exit:\r
- xor ax, ax\r
- .leave ARG_SIZE\r
-mxEllipse ENDP\r
-\r
-MX_TEXT ENDS\r
-END\r
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