使位图的某些区域在触摸时透明 [英] Make certain area of bitmap transparent on touch
本文介绍了使位图的某些区域在触摸时透明的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我的想法是将 2 个图像相互重叠并在 onTouch 上重叠,顶部图像应该在触摸半径上透明,从而暴露底部图像.
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.
这就是我叠加两张图片的方式:
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);
我查看了这篇文章像下面这样绘制以使其透明:
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
}
问题是,我认为圆立即使 2 个图像在定义的半径上透明,如何仅使顶部位图透明?
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?
推荐答案
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);
}
}
}
这篇关于使位图的某些区域在触摸时透明的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文