Draw some interesting figures with flutter's canvas

brief introduction

In the last article, we introduced the use of Flutter Of Canvas An example of drawing basic graphics , Simple examples are no fun , In today's article, let's have some interesting , We will complete the following drawing ：

1. Discover the beauty of mathematical repetition ： Use equilateral triangles to form a rainbow umbrella surface .
2. Drawing a rainbow .
3. Draw a five pointed star for scoring .

Through this article , We can know the basic principle of custom shape drawing , Then you can draw the figure you want to draw on this basis .

Equilateral triangles build the beauty of repetition

First, let's draw an equilateral triangle , In fact, in the last article, we also drew equilateral triangles , It's just that the three vertices are calculated manually , In this article, we encapsulate a general method for drawing equilateral triangles . Old rules , First define the input parameters of the method , As shown below ：

• canvas：Canvas canvas
• color： Draw colors
• startVertex： The position of the first vertex of the triangle , Here, our other edges rotate relative to this point
• length： Side length
• startAngle： The angle at which the first edge rotates relative to the horizontal direction , In this way, we can change the included angle to change the drawing position of the triangle .
• clockwise： Draw clockwise , If it's clockwise , Then the offset angle drawn starts clockwise , Otherwise, counterclockwise .
• filled： Whether to fill the drawing .

void drawEquilateralTriangle(
    Canvas