从 Android Canvas 获取像素值
我目前正在使用 SurfaceView 编写 Android 游戏。我已经尽可能地优化了游戏，并且运行起来非常流畅。但是，我合并了碰撞检测，这有点混乱。我想通过直接从画布读取像素来进行碰撞检测。这可以吗？我发现的最接近的方法是使用 setBitmap 将新位图附加到画布。然后，当我绘制到画布上时，位图将会更新。这是要走的路吗？谢谢。
I'm currently writing an Android game using surfaceView. I've optimized the game as much as possible and it runs quite smoothly. However, I have collision detection incorporated which is a bit messy. I would like to do collision detection by reading pixels directly from the canvas. Is this possible to do? The closest to this that I have found was to attach a new bitmap to the canvas using setBitmap. Then when I drew to the canvas, the bitmap would be updated. Would this be the way to go? Thanks.
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尽管您应该以不同的方式管理碰撞检测，但您可以使用下一行代码获取给定位置上的像素颜色：
mView 是包含画布的视图，mBitmap 是用于创建画布的位图：
Although you should manage the collision detection in a different way, you can get the pixel color on a given position with the next line of code:
mView is the View that contains your canvas and mBitmap is the Bitmap with which you created your canvas:
来自 Canvas API：
因此，您永远不会向画布询问像素数据，因为画布本身并不真正“拥有”像素数据。用于进行绘制调用的画布始终附加到位图（您正在其上绘制的位图），因此该位图是您应该从中获取像素数据的位置。
碰撞检测通常成本高昂，但采用基于位图的流程可能会使情况变得更糟，具体取决于您想要做什么。请注意。
From the Canvas API:
So you wouldn't ever ask a canvas for pixel data, because the canvas itself doesn't really "own" pixel data. The canvas which you use to make draw calls is always attached to a bitmap (the one you're drawing on), so that bitmap is where you should get your pixel data from.
Collision detection is usually costly, but going to a bitmap-based process could make it even worse, depending on what you're trying to do. Just a heads up.
我同意乔希的观点。如果精度在您的应用程序中如此重要，您可能希望将屏幕尺寸/分辨率数据合并到某种物理引擎中。尝试构建完全基于视觉处理的物理引擎可能会花费不必要的成本。
I agree with Josh. If precision is that important in your app, you may want to incorporate screen size/resolution data into some kind of physics engine. Trying to build a physics engine based entirely on visual processing is probably unnecessarily costly.