如何在android中blit()? [英] How to blit() in android?
问题描述
我习惯于使用老式库(allegro、GD、pygame)处理图形，如果我想将位图的一部分复制到另一个...我只使用 blit.
I'm used to handle graphics with old-school libraries (allegro, GD, pygame), where if I want to copy a part of a bitmap into another... I just use blit.
我试图弄清楚如何在 android 中做到这一点，但我很困惑.所以......我们有这些只写的画布和只读的位图?这似乎太愚蠢了，不可能是真的，一定是我遗漏了什么，但我真的想不通.
I'm trying to figure out how to do that in android, and I got very confused. So... we have these Canvas that are write-only, and Bitmaps that are read-only? It seems too stupid to be real, there must be something I'm missing, but I really can't figure it out.
编辑:更准确地说...如果位图是只读的，而画布是只写的，我不能将 A 写入 B，然后将 B 写入 C?
推荐答案
复制一个位图到另一个位图的代码是这样的:
The code to copy one bitmap into another is like this:
Rect src = new Rect(0, 0, 50, 50);
Rect dst = new Rect(50, 50, 200, 200);
canvas.drawBitmap(originalBitmap, src, dst, null);
这指定您要复制位图的左上角 (50x50)，然后将其拉伸为 150x150 位图，并将其写入距画布左上角 50 像素的偏移处.
That specifies that you want to copy the top left corner (50x50) of a bitmap, and then stretch that into a 150x150 Bitmap and write it 50px offset from the top left corner of your canvas.
您可以通过 invalidate() 触发绘图，但如果您正在制作动画，我建议您使用 SurfaceView.invalidate 的问题是它只在线程空闲时才绘制，所以你不能在循环中使用它 - 它只会绘制最后一帧.以下是我回答的有关图形的其他问题的一些链接，它们可能有助于解释我的意思.
You can trigger drawing via invalidate() but I recommend using a SurfaceView if you're doing animation. The problem with invalidate is that it only draws once the thread goes idle, so you can't use it in a loop - it would only draw the last frame. Here are some links to other questions I've answered about graphics, they might be of use to explain what I mean.
- 如何绘制矩形(空或已填充，以及其他一些选项)
- 如何为动画创建自定义 SurfaceView 带有随机弹跳球的应用的
- 代码链接在屏幕上，还包括触摸控制
- 有关 SurfaceView 的更多信息与 Invalidate() 对比
- 手动旋转事物的一些困难
- How to draw a rectangle (empty or filled, and a few other options)
- How to create a custom SurfaceView for animation
- Links to the code for an app with randomly bouncing balls on the screen, also including touch control
- Some more info about SurfaceView versus Invalidate()
- Some difficulties with manually rotating things
为了回应评论，这里有更多信息:如果您从 SurfaceHolder.lockCanvas() 获取 Canvas，那么我认为您无法将其中的残留数据复制到位图中.但这不是该控件的用途 - 只有在您整理好所有内容并准备好绘制时才使用.
In response to the comments, here is more information: If you get the Canvas from a SurfaceHolder.lockCanvas() then I don't think you can copy the residual data that was in it into a Bitmap. But that's not what that control is for - you only use than when you've sorted everything out and you're ready to draw.
您要做的是创建一个使用
What you want to do is create a canvas that draws into a bitmap using
Canvas canvas = new Canvas(yourBitmap)
然后您可以进行任何您想要的转换和绘图操作.yourBitmap 将包含所有最新信息.然后像这样使用表面支架:
You can then do whatever transformations and drawing ops you want. yourBitmap will contain all the newest information. Then you use the surface holder like so:
Canvas someOtherCanvas = surfaceHolder.lockCanvas()
someOtherCanvas.drawBitmap(yourBitmap, ....)
这样你就可以得到你的位图，里面有你想要保留的任何信息.
That way you've always got yourBitmap which has whatever information in it you're trying to preserve.
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