詳解iPhone開發Quratz 2D學習

iPhone開發Quratz 2D學習是本文要介紹的內容，主要講解的是如何來使用Quratz 2D，一起來看詳細內容。

1.graphics context圖形上下文）是一個不透明的資料類型CGContextRef）。我們可以把graphics context想象成為一個繪圖目標。有幾種graphics context：bitmap graphics context，PDF graphics context，window graphics context，layer context。

2.IOS中獲得graphics context是在方法drawRect：中，調用方法UIGraphicsGetCurrentContext得到上下文。drawRect：方法不需要調用super

 

  
CGContextRef c = UIGraphicsGetCurrentContext(); 
 

3.調用方法CGContextMoveToPoint開始一個新的路徑，

調用方法CGContextAddLineToPoint添加一個單一的線條。

4.When you want to construct a path in a graphics context, you signal Quartz by calling the function CGContextBeginPath . Next, you set the starting point for the first shape, or subpath, in the path by calling the function CGContextMoveToPoint. After you establish the first point, you can add lines, arcs, and curves to the path, keeping in mind the following:

Before you begin a new path, call the function CGContextBeginPath.

Lines, arcs, and curves are drawn starting at the current point. An empty path has no current point; you must call CGContextMoveToPoint to set the starting point for the first subpath or call a convenience function that implicitly does this for you.

When you want to close the current subpath within a path, call the function CGContextClosePath to connect a segment to the starting point of the subpath. Subsequent path calls begin a new subpath, even if you do not explicitly set a new starting point.

When you draw arcs, Quartz draws a line between the current point and the starting point of the arc.

Quartz routines that add ellipses and rectangles add a new closed subpath to the path.

You must call a painting function to fill or stroke the path because creating a path does not draw the path. See “Painting a Path” for detailed information.

小結：詳解iPhone開發Quratz 2D學習的內容介紹完了，希望通過本文的學習能對你有所協助！