我目前正在寻找一种方法来使用黑白位图来遮罩另一个位图或可在Android上绘制的alpha通道。我很好奇做这件事最好的方法是什么。我当然有几个关于如何做到这一点的想法,但它们并不是最佳的。
我需要能够将新的蒙版应用到图像中(黑白位图每隔几秒钟就会改变一次)。
任何关于如何实现这一点的反馈都将非常感谢。
发布于 2012-10-13 04:19:48
我让它工作了,所以它是这样的
// we first same the layer, rectF is the area of interest we plan on drawing
// this will create an offscreen bitmap
canvas.saveLayer(rectF, null, Canvas.MATRIX_SAVE_FLAG
| Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
| Canvas.FULL_COLOR_LAYER_SAVE_FLAG
| Canvas.CLIP_TO_LAYER_SAVE_FLAG);
// draw our unmasked stuff
super.draw(canvas);
// We same a layer again but this time we pass a paint object to mask
// the above layer
maskPaint = new Paint()
maskPaint.setColor(0xFFFFFFFF);
maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY));
canvas.saveLayer(rectF, maskPaint,
Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG
| Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
| Canvas.FULL_COLOR_LAYER_SAVE_FLAG
| Canvas.CLIP_TO_LAYER_SAVE_FLAG);
// we draw the mask which is black and white. In my case
// I have a path, and I use a blurPaint which blurs the mask slightly
// You can do anti aliasing or whatever you which. Just black & white
canvas.drawPath(path, blurPaint);
// We restore twice, this merges the results upward
// as each saveLayer() allocates a new drawing bitmap
canvas.restore();
canvas.restore();
发布于 2014-07-31 00:04:06
我的解决方案与@over_optimistic的解决方案非常接近,只需少一次saveLayer()调用。我使用可抽出的遮罩而不是路径,在我的例子中它是一张光盘。
我将这些变量声明为字段(最好在onDraw方法之外分配内存):
private Paint maskingPaint = new Paint();
private Drawable mask = <insert your drawable here>
然后,在onDraw()之外的某个地方设置对象:
// Xfermode won't work if hardware accelerated
setLayerType(View.LAYER_TYPE_SOFTWARE, null);
// Using destination shape as a mask
// For a good explanation of PorterDuff transfer modes : http://ssp.impulsetrain.com/porterduff.html
maskingPaint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
maskingPaint.setAntiAlias(true);
// Position the mask
mask.setBounds(<insert your mask bounds here>);
最后,onDraw()方法应用掩码:
@Override
protected synchronized void onDraw(Canvas canvas)
{
// Draw the mask first, making it the PorterDuff destination
mask.draw(canvas);
// Save the layer with the masking paint, that will be applied on restore()
// Using CLIP_TO_LAYER_SAVE_FLAG to avoid any overflow of the masked image outside the mask bounds.
Rect bounds = mask.getBounds();
canvas.saveLayer(bounds.left, bounds.top, bounds.right, bounds.bottom, maskingPaint,
Canvas.CLIP_TO_LAYER_SAVE_FLAG);
// Draw the shape offscreen, making it the PorterDuff source
super.onDraw(canvas);
// Apply the source to the destination, using SRC_IN transfer mode
canvas.restore();
}
为了更好地理解传输模式,我参考了http://ssp.impulsetrain.com/porterduff.html。这个页面读起来很有趣。在那之后,用同样的代码,你将能够获得比简单的掩码更多的东西!
发布于 2014-07-26 19:40:17
我做了一个可屏蔽的布局。这是一个框架布局,您可以在其中指定xporterduffmode和掩码。你可以在这里找到它:https://github.com/christophesmet/android_maskable_layout
https://stackoverflow.com/questions/2623888
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