让触摸位图的特定区域透明 [英] Make certain area of bitmap transparent on touch
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问题描述
我的想法是在彼此并且在onTouch顶部重叠2个图像，顶图像应是触摸半径上进行透明的，从而暴露底图像
这是我如何叠加2图像：
位图bmOverlay = Bitmap.createBitmap（bmp1.getWidth（），bmp1.getHeight（），bmp1.getConfig（））;
帆布油画=新的Canvas（bmOverlay）;
canvas.drawBitmap（BMP1，新的Matrix（），NULL）;
canvas.drawBitmap（BMP2，新的Matrix（），NULL）;
我已经研究过<一个href="http://stackoverflow.com/questions/3021401/making-overlaid-image-transparent-on-touch-in-android">this帖子并有漆像下面，使之透明：
mPaint =新的油漆（）;
mPaint.setXfermode（新PorterDuffXfermode（PorterDuff.Mode.SRC））;
mPaint.setColor（Color.TRANSPARENT）;
mPaint.setAntiAlias（真正的）;
公共无效的OnDraw（帆布油画）{
canvas.drawCircle（40，40，30，mPaint）; //硬code测试
}
但问题是，我想了一圈马上使2图像透明定义的半径，我怎样才能使只有最上面的位图透明？
解决方案
进口android.app.Activity;
进口android.content.Context;
进口android.graphics.Bitmap;
进口android.graphics.Bitmap.Config;
进口android.graphics.BlurMaskFilter.Blur;
进口android.graphics.BitmapFactory;
进口android.graphics.BlurMaskFilter;
进口android.graphics.Canvas;
进口android.graphics.Color;
进口android.graphics.Paint;
进口android.graphics.PorterDuff.Mode;
进口android.graphics.PorterDuffXfermode;
进口android.os.Bundle;
进口android.view.MotionEvent;
进口android.view.View;
公共类StartActivity延伸活动{
@覆盖
公共无效的onCreate（包savedInstanceState）{
super.onCreate（savedInstanceState）;
的setContentView（新的TouchView（本））;
}
一流的TouchView扩展视图{
位图BGR;
位图overlayDefault;
位图覆盖;
涂料pTouch;
INT X = -100;
INT Y = -100;
帆布带C2;
公众的TouchView（上下文的背景下）{
超（上下文）;
BGR = BitmapFactory.de codeResource（getResources（），R.drawable.bgr）;
overlayDefault = BitmapFactory.de codeResource（getResources（），R.drawable.over）;
覆盖= BitmapFactory.de codeResource（getResources（），R.drawable.over）.copy（Config.ARGB_8888，真正的）;
C2 =新的Canvas（叠加）;
pTouch =新的油漆（Paint.ANTI_ALIAS_FLAG）;
pTouch.setXfermode（新PorterDuffXfermode（Mode.SRC_OUT））;
pTouch.setColor（Color.TRANSPARENT）;
pTouch.setMaskFilter（新BlurMaskFilter（15，Blur.NORMAL））;
}
@覆盖
公共布尔的onTouchEvent（MotionEvent EV）{
开关（ev.getAction（））{
案例MotionEvent.ACTION_DOWN：{
X =（int）的ev.getX（）;
Y =（INT）ev.getY（）;
无效（）;
打破;
}
案例MotionEvent.ACTION_MOVE：{
X =（int）的ev.getX（）;
Y =（INT）ev.getY（）;
无效（）;
打破;
}
案例MotionEvent.ACTION_UP：
打破;
}
返回true;
}
@覆盖
公共无效的OnDraw（帆布油画）{
super.onDraw（画布）;
//画背景
canvas.drawBitmap（BGR，0，0，NULL）;
//复制默认覆盖到临时覆盖，并打一个洞，这
c2.drawBitmap（overlayDefault，0，0，NULL）; //排除这条线来显示所有在绘制
c2.drawCircle（X，Y，80，pTouch）;
//绘制叠加在背景上
canvas.drawBitmap（叠加，0，0，NULL）;
}
}
}
My idea is to overlap 2 images on top of each other and upon onTouch, the top image should be made transparent on that touched radius, thus exposing the bottom image.
This is how I overlay the 2 images:
Bitmap bmOverlay = Bitmap.createBitmap(bmp1.getWidth(), bmp1.getHeight(), bmp1.getConfig());
Canvas canvas = new Canvas(bmOverlay);
canvas.drawBitmap(bmp1, new Matrix(), null);
canvas.drawBitmap(bmp2, new Matrix(), null);
I have looked into this post and have a Paint like below to make it transparent:
mPaint = new Paint();
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
mPaint.setColor(Color.TRANSPARENT);
mPaint.setAntiAlias(true);
public void onDraw(Canvas canvas) {
canvas.drawCircle(40, 40, 30, mPaint); //hardcode to test
}
Problem is, I think the circle straight away make the 2 images transparent on the defined radius, how can I make only the top bitmap transparent?
解决方案
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BlurMaskFilter.Blur;
import android.graphics.BitmapFactory;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
public class StartActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new TouchView(this));
}
class TouchView extends View{
Bitmap bgr;
Bitmap overlayDefault;
Bitmap overlay;
Paint pTouch;
int X = -100;
int Y = -100;
Canvas c2;
public TouchView(Context context) {
super(context);
bgr = BitmapFactory.decodeResource(getResources(),R.drawable.bgr);
overlayDefault = BitmapFactory.decodeResource(getResources(),R.drawable.over);
overlay = BitmapFactory.decodeResource(getResources(),R.drawable.over).copy(Config.ARGB_8888, true);
c2 = new Canvas(overlay);
pTouch = new Paint(Paint.ANTI_ALIAS_FLAG);
pTouch.setXfermode(new PorterDuffXfermode(Mode.SRC_OUT));
pTouch.setColor(Color.TRANSPARENT);
pTouch.setMaskFilter(new BlurMaskFilter(15, Blur.NORMAL));
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN: {
X = (int) ev.getX();
Y = (int) ev.getY();
invalidate();
break;
}
case MotionEvent.ACTION_MOVE: {
X = (int) ev.getX();
Y = (int) ev.getY();
invalidate();
break;
}
case MotionEvent.ACTION_UP:
break;
}
return true;
}
@Override
public void onDraw(Canvas canvas){
super.onDraw(canvas);
//draw background
canvas.drawBitmap(bgr, 0, 0, null);
//copy the default overlay into temporary overlay and punch a hole in it
c2.drawBitmap(overlayDefault, 0, 0, null); //exclude this line to show all as you draw
c2.drawCircle(X, Y, 80, pTouch);
//draw the overlay over the background
canvas.drawBitmap(overlay, 0, 0, null);
}
}
}
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