如何块复制（）中的机器人？ [英] How to blit() in android?

问题描述

我已经习惯了处理与老派的图形库（快板，GD，pygame的），在那里，如果我想要一个位图的一部分复制到另一个......我只是用块传送。

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.

我试图找出如何做到这一点在Android中，和我很困惑。 所以......我们这些帆布是只写和位图是只读的是什么？这似乎太愚蠢是真实的，一定是有什么我失踪，但我真的不明白。

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.

修改的：更precise ... 如果位图是只读的，和帆布是只写，我不能块复制阿成B，然后B插入C 2

edit: to be more precise... if bitmaps are read only, and canvas are write only, I can't blit A into B, and then B into C?

推荐答案

在code复制一个位图到另一个是这样的：

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);

这指定要复制一个位图的左上角（50×50），然后伸了成150×150点阵，并写50像素的画布的左上角偏移。

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.

您可以通过触发无效（）画，但我建议使用SurfaceView如果你正在做动画。与无效的问题是，它只能绘制一旦线程进入闲置状态，因此你不能用它在一个循环 - 它只能绘制的最后一帧。这里有一些链接到其他的问题我已经回答了有关图形，他们可能会使用来解释我的意思。

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.

• <一个href="http://stackoverflow.com/questions/2539396/new-to-android-drawing-a-view-at-runtime/2539549#2539549">How绘制一个矩形（空或填充，以及一些其他选项）
• <一个href="http://stackoverflow.com/questions/2554871/android-how-to-position-view-off-screen/2560731#2560731">How创建一个自定义的SurfaceView动画
• <一个href="http://stackoverflow.com/questions/2564171/view-animation-resizing-a-ball/2564483#2564483">Links为一个应用程序的code ，并在屏幕上随机弹跳球，还包括触摸控制
• <一个href="http://stackoverflow.com/questions/2438733/how-to-do-animations-in-android-chess-game/2438763#2438763">Some更多信息有关SurfaceView对的Invalidate（）
• <一个href="http://stackoverflow.com/questions/2439301/animating-and-rotating-an-image-in-a-surface-view/2439548#2439548">Some与手动旋转的东西
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

在响应于该评论，这里是信息 如果从SurfaceHolder.lockCanvas获得画布（），那么我不认为你可以复制那是在它变成一个位图的剩余数据。但是，这并不是该控制什么 - 你只比当你排序的一切使用了，你准备好绘制

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.

您想要做的是创建一个画布绘制成位图使用

What you want to do is create a canvas that draws into a bitmap using

Canvas canvas = new Canvas(yourBitmap)

您就可以做任何的转换和绘图OPS你想要的。 yourBitmap将包含所有最新的信息。 然后的使用表面支架，像这样：

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，你总是在不知不觉yourBitmap有任何信息在里面你想preserve。

That way you've always got yourBitmap which has whatever information in it you're trying to preserve.

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