Question

我在Uni有一个任务，涉及绘制许多不同的形状，所有这些都必须使用C语言的gdImage库绘制。到目前为止，我已使用gdImageLine和gdImageRectangle，如下所示：

gdImageLine ( gdImage, 150, 70, 170, 90, blue);

或

gdImageRectangle( gdImage, 110, 80, 160, 120, blue);

我非常缺乏经验/对C没有任何线索，所以任何帮助都会很棒！

嗨，抱歉我感到困惑。我想使用“gdImagePolygon”绘制一个形状/类似于我如何使用其他两个，如果这有意义的话？我已收到此链接（http://cnfolio.com/public/libgd_drawing_reference.html），谢谢

Answer 1

gdImagePolygon具有以下签名：

gdImagePolygon(gdImagePtr im, gdPointPtr points, int pointsTotal, int color)

gdImagePtr是指向gdImage Structure

的指针

gdPointPtr是指向gdPoint structure的指针（只有两个ints，x和y）：

typedef struct {
    int x, y;
} gdPoint, *gdPointPtr;

pointsTotal是您将获得的积分总数（最少3个）

color是颜色

绘制三角形的样本：

... inside a function ...
gdImagePtr im;
int black;
int white;
/* Points of polygon */
gdPoint points[3];           // an array of gdPoint structures is used here
im = gdImageCreate(100, 100);
/* Background color (first allocated) */
black = gdImageColorAllocate(im, 0, 0, 0);  
/* Allocate the color white (red, green and 
  blue all maximum). */
white = gdImageColorAllocate(im, 255, 255, 255);  
/* Draw a triangle. */
points[0].x = 50;
points[0].y = 0;
points[1].x = 99;
points[1].y = 99;
points[2].x = 0;
points[2].y = 99;
gdImagePolygon(im, points, 3, white);
/* ... Do something with the image, such as 
  saving it to a file... */
/* Destroy it */
gdImageDestroy(im);

Answer 2

我从头开始编写此代码段，如果有任何错误，请通知我。感谢。

int Draw_Polygon (int Side, ...)
{
    va_list Ap;
    va_start (Ap, Side);
    int X_1 = va_arg (Ap, int);
    int X_0 = X_1;
    int Y_1 = va_arg (Ap, int);
    int Y_0 = Y_1;
    int Cnt;
    for (Cnt = 0; Cnt < Side-1; Cnt++)
    {
        int X_2 = va_arg (Ap, int);
        int Y_2 = va_arg (Ap, int);
        gdImageLine ( gdImage, X_1, Y_1, X_2, Y_2, blue);
        X_1 = X_2;
        Y_1 = Y_2;
    }
    gdImageLine ( gdImage, X_1, Y_1, X_0, Y_0, blue);
    va_end(Ap);
    return 0;
}

int main (void)
{
    if (Draw_Polygon (5, 0, 0, 0, 10, 12, 12, 16, 8, 5, 0) == 0) // Draw a pentagon.
    {
         // Success !
    }

    if (Draw_Polygon (6, 0, 0, 0, 10, 12, 12, 16, 8, 6, 3, 5, 0) == 0) // Draw a hexagon.
    {
         // Success !
    }
}

Answer 3

快速伪代码绘制N边的多边形，边长为L：

Procedure DrawPol (integer N,L)
  Integer i
  For i=1 To N
    Draw (L)
    Turn (360/N)
  EndFor
EndProcedure

这个伪代码基于两个原语，这些原语在LOGO：

等语言中很常见

Draw (L)：在当前方向绘制一行L像素
Turn (A)：通过向A度添加Draw度来更改当前方向当前方向

要使用Turn功能实施Line和Real CurrentAngle = 0 /* global variable */ Integer CurrentX = MAXX / 2 /* last point drawn */ Integer CurrentY = MAXY / 2 /* initialized to the center of the paint area */ Procedure Draw (Integer L) Integer FinalX,FinalY FinalX = CurrentX + L*cos(CurrentAngle) FinalY = CurrentY + L*sin(CurrentAngle) Line (CurrentX, CurrentY, FinalX, FinalY) /* gdImageLine() function actually */ CurrentX = FinalX CurrentY = FinalY EndProcedure Procedure Turn (Float A) CurrentAngle = CurrentAngle + A If (CurrentAngle>360) /* MOD operator usually works */ CurrentAngle = 360-CurrentAngle /* only for integers */ EndIf EndProcedure，您可以使用以下内容：

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如何在C中使用getimage绘制多边形？

3 个答案: