如何在XNA中绘制具有特定颜色的圆？ [英] How to draw circle with specific color in XNA?

问题描述

XNA没有任何支持圆圈绘制的方法。

通常，当我不得不绘制圆圈时，总是使用相同的颜色，我只是使用该圆圈创建图像，然后可以将其显示为

但是现在圆的颜色是在运行时指定的，任何想法如何处理呢？

XNA doesn't have any methods which support circle drawing.
Normally when I had to draw circle, always with the same color, I just made image with that circle and then I could display it as a sprite.
But now the color of the circle is specified during runtime, any ideas how to deal with that?

推荐答案

您可以简单地使用透明背景创建圆形的图像，圆形的彩色部分为白色。然后，当在 Draw（）方法中绘制圆形时，选择色调作为您想要的颜色：

You can simply make an image of a circle with a Transparent background and the coloured part of the circle as White. Then, when it comes to drawing the circles in the Draw() method, select the tint as what you want it to be:

Texture2D circle = CreateCircle(100);

// Change Color.Red to the colour you want
spriteBatch.Draw(circle, new Vector2(30, 30), Color.Red); 

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为了有趣，这里是CreateCircle方法：

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Just for fun, here is the CreateCircle method:

    public Texture2D CreateCircle(int radius)
    {
        int outerRadius = radius*2 + 2; // So circle doesn't go out of bounds
        Texture2D texture = new Texture2D(GraphicsDevice, outerRadius, outerRadius);

        Color[] data = new Color[outerRadius * outerRadius];

        // Colour the entire texture transparent first.
        for (int i = 0; i < data.Length; i++)
            data[i] = Color.TransparentWhite;

        // Work out the minimum step necessary using trigonometry + sine approximation.
        double angleStep = 1f/radius;

        for (double angle = 0; angle < Math.PI*2; angle += angleStep)
        {
            // Use the parametric definition of a circle: http://en.wikipedia.org/wiki/Circle#Cartesian_coordinates
            int x = (int)Math.Round(radius + radius * Math.Cos(angle));
            int y = (int)Math.Round(radius + radius * Math.Sin(angle));

            data[y * outerRadius + x + 1] = Color.White;
        }

        texture.SetData(data);
        return texture;
    }

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