`` ``` case WM_PAINT: { PAINTSTRUCT ps; HDC hdc = BeginPaint(hWnd, &ps); // TODO: 在此處添加使用 hdc 的任何繪圖代碼... // double slope = 0.6;// 0.75;// 當斜率大于1的時候,繪圖要反轉,即以y和 DeltaY為循環變量! //1.75;// 0.75;// deltY/deltX=1.45 即斜率(y2-y1)/(x2-x1)=1.75 int x100 = 1000;// 100; int x500 = 5000;// 500; int y100 = 1000;// 100; int y400 = 4000;// 400; MoveToEx(hdc, 50, 10, NULL); Rectangle(hdc, x100, y100, x500, y400); INT64 maxY; maxY = 2 ^ 63 - 1; INT64 x1 = 100; double dx1 = (double)x1; INT64 x2 = x1; double dx2 = (double)x2; INT64 y1 = 100; double dy1 = (double)y1; INT64 y2 = y1; double dy2 = (double)y2; int flagx = 1; int flagy = 1; int flagy0 = 0;// -1; //flagy0比較晦澀難懂, 有時精密計算的結果是 y2多次等于邊界 y400等,當是第一次的時候 就反轉 // for (INT64 ii = 100; ii < 99999; ++ii) {//for110 //x1 = ixi;// / 10; //精密到 0.1 //dx1 = (double)x1; aboutFlag: //x1 = (int)dx1; if (x100 >= (x1/1) ) { //if (100 == (x1/10) ) { flagx = 1; } if (x500 <= (x1/1)) {//if (x500 == (x1/10)) { flagx = -1; } y1 = (int)dy1;//把y的坐標找出來變成整數 if (y100 >= y1) {//if (y100 == y1) { flagy = 1; } //if (0==flagy0 && y400 == (int)(y1/1) ) { //if (y400 == (int)(y1/10) || (4000==(int)y1 ) ) { if ( y400 <= (int)y1) { //(int)(y1 / 1)) { flagy = -1; flagy0 = 2; } if (100 == x1 && 100 == y1) { flagx = 1; flagy = 1; } //這個點特殊,這是光源,或笛卡爾坐標原點 //aboutFlag-End; label_Y_as_aVar: x2 = x1 + (flagx) * 1; dx2 = dx1 + (flagx) * 1; INT64 deltaX = labs(long(x2 - x1)); dy2 = (flagy)*deltaX*slope + dy1; // SetPixel(hdc, (x2/1), (int)(dy2/1), RGB(1, 200, 0)); // SetPixel(hdc, (x2/10), (int)(dy2/10), RGB(1, 200, 0)); // labelEnd990: x1 = x2; dx1 = dx2; if (y1 != y2) { flagy0 = 0; }//此舉回復反轉開關 y1 = y2; dy1 = dy2; }//for110 // // EndPaint(hWnd, &ps); }//case WM_PAINT: break; //......省略 // case WM_DESTROY: ```