如何在Android中吸取位图？ [英] How to draw on Bitmap in android?

问题描述

我试图找出如何利用android的位图，并保持这些变化的位图的副本撤消功能。

I'm trying to figure out how to draw on a bitmap in android, and keep a copy of these changed bitmaps for an undo function.

Bitmap b = ...
Paint p = new Paint();
canvas.drawBitmap(b, new Matrix(), null);
canvas.drawCircle(0,0,20,20);
//does Bitmap b have the circle drawn on it next time?

或如何得到位图后，它被画在与画布（我想preserve一叠位图与绘图画布应用的变化）？也许我会对此完全错误的。

Or how do I get the bitmap after its been drawn on with the canvas(I want to preserve a stack of bitmaps with the changes applied by canvas drawing)? Maybe I'm going about this entirely wrong.

推荐答案

使用<一个href="http://developer.android.com/reference/android/graphics/Canvas.html#Canvas%28android.graphics.Bitmap%29"><$c$c>new帆布（位图位图） 提供了画布与位图这将包含绘图操作的结果。

Use new Canvas(Bitmap bitmap) to provide a Canvas with a Bitmap which will contain the result of your drawing operations.

原位图，你利用你的画布与 drawBitmap 将永远不会被修改。

The original Bitmap that you draw on your Canvas with drawBitmap will never be modified.

由用户来完成每一个操作之后，您可能：

After each operation done by the user you might:

• 保存在内存中进行的操作的列表
• 在保存中间结果到外部存储与Bitmap.com preSS

另一种方法可以是使用一个<一href="http://developer.android.com/intl/fr/reference/android/graphics/drawable/LayerDrawable.html"><$c$c>LayerDrawable堆叠在彼此的顶部连续绘图操作。你可以想像，允许用户禁用每个单独的操作完成。

Another approach could be to use a LayerDrawable to stack successive drawing operations on top of each other. You can imagine allowing the user to disable each individual operation done.

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