如何计算android中位图的擦除区域的百分比？

概述我是 android的新手.我正在做一个可以用手指擦除画布上的位图的应用程序.像手指画橡皮擦的东西.我想计算擦除区域的百分比(例如,60％已从完整图像中删除).请帮我这样做..提前致谢.. 我尝试了一些方法.它总是给我0％.它不起作用.请参阅该方法的代码底部.. 自定义视图 public class MyView extends View{ private final Paint mPa 我是 android的新手.我正在做一个可以用手指擦除画布上的位图的应用程序.像手指画橡皮擦的东西.我想计算擦除区域的百分比(例如,60％已从完整图像中删除).请帮我这样做..提前致谢..

我尝试了一些方法.它总是给我0％.它不起作用.请参阅该方法的代码底部..

自定义视图

public class MyVIEw extends VIEw{    private final Paint mPaint;    private Bitmap mBitmap;    private Canvas mCanvas;    private final Path mPath;    private final Paint mBitmapPaint;    private Bitmap eraseableBitmap;    public MyVIEw(Context context)    {        super(context);        if (Build.VERSION.SDK_INT >= 11)        {            setLayerType(VIEw.LAYER_TYPE_SOFTWARE,null);        }        mPaint = new Paint();        mPath = new Path();        mBitmapPaint = new Paint(Paint.DITHER_FLAG);    }    protected voID PaintObjectinit()    {        mPaint.setAntiAlias(true);        mPaint.setDither(true);        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));        mPaint.setStyle(Paint.Style.stroke);        mPaint.setstrokeJoin(Paint.Join.ROUND);        mPaint.setstrokeCap(Paint.Cap.ROUND);        mPaint.setstrokeWIDth(30);    }    @OverrIDe    protected voID onSizeChanged(int w,int h,int olDW,int oldh)    {        super.onSizeChanged(w,h,olDW,oldh);        try        {            //mBitmap = Bitmap.createBitmap(w,Bitmap.Config.ARGB_8888);            eraseableBitmap =                BitmapFactory.decodeResource(this.getResources(),R.drawable.tharu_rena_over).copy(                    Bitmap.Config.ARGB_8888,true);            eraseableBitmap = getResizedBitmap(eraseableBitmap,w);            mCanvas = new Canvas(eraseableBitmap );        }        catch (Exception e)        {            // Todo: handle exception            e.printstacktrace();        }    }    public Bitmap getResizedBitmap(Bitmap bm,int newHeight,int newWIDth)    {        int wIDth = bm.getWIDth();        int height = bm.getHeight();        float scaleWIDth = ((float) newWIDth) / wIDth;        float scaleHeight = ((float) newHeight) / height;        // CREATE A MATRIX FOR THE MANIPulATION        Matrix matrix = new Matrix();        // RESIZE THE BIT MAP        matrix.postscale(scaleWIDth,scaleHeight);        // "RECREATE" THE NEW BITMAP        Bitmap resizedBitmap = Bitmap.createBitmap(bm,wIDth,height,matrix,false);        return resizedBitmap;    }    @OverrIDe    protected voID onDraw(Canvas canvas)    {        //canvas.drawBitmap(mBitmap,mBitmapPaint);        canvas.drawBitmap(eraseableBitmap,mBitmapPaint);        canvas.drawPath(mPath,mPaint);    }    private float mX,mY;    private static final float touch_TolERANCE = 4;    private voID touch_start(float x,float y)    {        //        mPath.reset();        mPath.moveto(x,y);        mX = x;        mY = y;    }    private voID touch_move(float x,float y)    {        float dx = Math.abs(x - mX);        float dy = Math.abs(y - mY);        if (dx >= touch_TolERANCE || dy >= touch_TolERANCE)        {            mPath.quadTo(mX,mY,(x + mX) / 2,(y + mY) / 2);            mX = x;            mY = y;        }    }    private voID touch_up()    {        mPath.lineto(mX,mY);        // commit the path to our offscreen        mCanvas.drawPath(mPath,mPaint);        // kill this so we don't double draw        Toast.makeText(getContext(),"Deleted: " + percenttransparent(eraseableBitmap,10),Toast.LENGTH_SHORT).show();    }    @OverrIDe    public boolean ontouchEvent(MotionEvent event)    {        float x = event.getX();        float y = event.getY();        switch (event.getAction())        {            case MotionEvent.ACTION_DOWN:                touch_start(x,y);                invalIDate();                break;            case MotionEvent.ACTION_MOVE:                touch_move(x,y);                invalIDate();                break;            case MotionEvent.ACTION_UP:                touch_up();                invalIDate();                break;        }        return true;    }    static public float percenttransparent(Bitmap bm,int scale)    {        final int wIDth = bm.getWIDth();        final int height = bm.getHeight();        // size of sample rectangles        final int xStep = wIDth / scale;        final int yStep = height / scale;        // center of the first rectangle        final int xInit = xStep / 2;        final int yInit = yStep / 2;        // center of the last rectangle        final int xEnd = wIDth - xStep / 2;        final int yEnd = height - yStep / 2;        int totaltransparent = 0;        for (int x = xInit; x <= xEnd; x += xStep)        {            for (int y = yInit; y <= yEnd; y += yStep)            {                if (bm.getPixel(x,y) == color.transparent)                {                    totaltransparent++;                }            }        }        return ((float) totaltransparent) / (scale * scale);    }}

内部活动类onCreate

try{    MyVIEw myVIEw = new MyVIEw(this);    myVIEw.requestFocus();    myVIEw.PaintObjectinit();    // setContentVIEw(myVIEw);    linearLayout upper = (linearLayout) findVIEwByID(R.ID.linearLayout01);    upper.addVIEw(myVIEw);}catch (Exception e){    // Todo: handle exception    e.printstacktrace();}

解决方法 问题是您无法调用PaintObjectinit()方法,因此您使用默认绘画进行绘制,因此使用color.BLACK而不是color.transparent进行绘制.在构造函数的底部添加对PaintObjectinit()的调用,它应该可以工作.

此外,以下创建一个不可变的位图！请参见createBitmap.因此,您的位图永远不会被修改.您通过绘制路径和位图将这一事实隐藏在用户界面上.

// "RECREATE" THE NEW BITMAPBitmap resizedBitmap = Bitmap.createBitmap(bm,false);return resizedBitmap;

尝试制作一个像这样的可变位图 –

// "RECREATE" THE NEW BITMAP        Bitmap resizedBitmap = Bitmap.createBitmap(newWIDth,newHeight,Bitmap.Config.ARGB_8888);        Canvas c = new Canvas(resizedBitmap);        c.setMatrix(matrix);        c.drawBitmap(bm,null);        return resizedBitmap;

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