如何調用Pie函數？

Question

我有繪製餅圖的中心點，半徑和角度，但the Pie function需要4點作爲輸入數據。有沒有人有任何轉換功能或更好的解釋呢？

Answer 1

的四點餅功能：

1. 上邊框的左上角。
2. 邊界矩形的右下角。
3. 指向標記餅圖開始的圓上的點。
4. 指向標記餡餅末端的圓圈（逆時針）。

轉換：

中心點：CX，賽揚 半徑，R 角度：一個

假設你的餡餅從高層開始。

1. X1 = CX-R，Y1 = CX + R
2. X2 = CX + R，Y2 =賽揚-R
3. X3 = CX，Y3 = Y1
4. X4 = CX + R罪（a），Y4 = Cy + rcos（a）

你可能不得不在某個地方翻轉一個標誌，但是這應該是有用的。

用兩個不同角度的（a和b）：

X3 = CX + R SIN（a）中，Y3 =賽揚+ R cos（A）

X4 = Cx + r sin（b），Y4 = Cy + r cos（b）

Answer 2

這是用（舊）C++編寫的，但大多數應該很容易地轉換爲Delphi（或幾乎任何其他）。它還假定輸入是以百分比（整圓爲100％）而不是原始角度，但（再次）應該很容易處理。它以弧度轉換百分比到角度，所以從其他單位轉換應該是一個很小的調整。

class section { 
    double percent; 
    int color; 
public: 

    section(double percent_, int color_) : 
     percent(percent_), color(color_) {} 

    void draw(HDC destination, POINT const &center, int diameter, double &start_angle); 
}; 

---

void section::draw(HDC destination, POINT const &center, int radius, double &start_angle) { 

    double start_x, start_y, end_x, end_y; 
    double angle, end_angle; 

    int top = center.y - radius; 
    int bottom = center.y + radius; 
    int left = center.x - radius; 
    int right = center.x + radius; 

    // now we have to convert a percentage to an angle in radians. 
    // there are 100 percent in a circle, and 2*PI radians in a 
    // circle, so we figure this percentage of 2*PI radians. 
    angle = percent/100.0 * 2.0 * 3.1416; 

    end_angle = start_angle + angle; 

    // Now we have to convert these angles into rectangular 
    // coordinates in the window, which depend on where we're 
    // putting the chart, and how big we're making it. 
    start_x = center.x + radius * cos(start_angle); 
    start_y = center.y + radius * sin(start_angle); 

    end_x = center.x + radius * cos(end_angle); 
    end_y = center.y + radius * sin(end_angle); 

    // Now we need to actually draw the pie section by selecting 
    // the correct color into the DC, drawing the section, then 
    // selecting the original brush back, and deleing our brush. 
    HBRUSH brush = CreateSolidBrush(color); 

    HBRUSH old_brush = (HBRUSH)SelectObject(destination, brush); 

    Pie(destination, left, top, right, bottom, 
     (int)start_x, (int)start_y, (int)end_x, (int)end_y); 

    SelectObject(destination, old_brush); 
    DeleteObject(brush); 

    // our sole awareness of other sections: the next section will 
    // start wherever we finished. 
    start_angle = end_angle; 
}