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安卓：使用贝塞尔的数字签名

android java bezier handwriting paint
2022-09-02 14:07:28

enter image description here
我正在尝试使用贝塞尔绘制数字签名，如上图所示，当我触摸并尝试绘制线条时，结果是点线，但没有得到连续的线条。通过使用简单的签名完成简单的签名，但我想使用Bezier在触摸压力下创建更平滑的曲线。尝试使用此链接

SignatureViewDemo.java

    public class SignatureViewDemo extends View {
        private int color = Color.BLACK;
        private Bitmap m_Bitmap;
        private final Paint m_BorderPaint;
        private Canvas m_Canvas;
        private Point m_CropBotRight;
        private Point m_CropTopLeft;
        private float m_CurrentX;
        private float m_CurrentY;
        private final float m_DesiredDash;
        private float m_LastWidth = 6.5F;
        private Paint m_PenPaint;
        private int m_PointIndex = 0;
        private ArrayList<Point> m_Points = new ArrayList<Point>();
        private final float m_StrokeWidth;
        boolean m_Empty;



    public SignatureViewDemo(Context paramContext) {

        this(paramContext, null);
    }

    public SignatureViewDemo(Context paramContext,
            AttributeSet paramAttributeSet) {
        this(paramContext, paramAttributeSet, 0);
    }

    public SignatureViewDemo(Context paramContext,
            AttributeSet paramAttributeSet, int paramInt) {
        super(paramContext, paramAttributeSet, paramInt);
        setFocusable(true);
        this.m_PenPaint = new Paint();
        this.m_PenPaint.setAntiAlias(true);
        this.m_PenPaint.setColor(Color.BLACK);
        this.m_PenPaint.setStrokeWidth(5.0F);
        this.m_PenPaint.setStrokeJoin(Paint.Join.ROUND);
        this.m_PenPaint.setStrokeCap(Paint.Cap.ROUND);
        this.m_CurrentY = (0.0F / 0.0F);
        this.m_CurrentX = (0.0F / 0.0F);
        this.m_StrokeWidth = 5.0F;
        this.m_DesiredDash = 10.0F;
        this.m_BorderPaint = new Paint();
        this.m_BorderPaint.setColor(Color.BLACK);
        this.m_BorderPaint.setStyle(Paint.Style.STROKE);
        this.m_BorderPaint.setStrokeWidth(this.m_StrokeWidth);
    }

    public void addBezier(Bezier paramBezier, float paramFloat1,
            float paramFloat2) {
        if (this.m_Bitmap == null) {
            this.m_Bitmap = Bitmap.createBitmap(getWidth(), getHeight(),
                    Bitmap.Config.ARGB_8888);
            this.m_Canvas = new Canvas(this.m_Bitmap);
        }
        paramBezier.draw(this.m_Canvas, this.m_PenPaint, paramFloat1,
                paramFloat2);
    }

    public void addPoint(Point paramPoint) {
        if ((paramPoint.getX() < this.m_CropTopLeft.getX())
                && (paramPoint.getX() >= 0.0F))
            this.m_CropTopLeft.setX(paramPoint.getX());
        if ((paramPoint.getY() < this.m_CropTopLeft.getY())
                && (paramPoint.getY() >= 0.0F))
            this.m_CropTopLeft.setY(paramPoint.getY());
        if ((paramPoint.getX() > this.m_CropBotRight.getX())
                && (paramPoint.getX() <= this.m_Canvas.getWidth()))
            this.m_CropBotRight.setX(paramPoint.getX());
        if ((paramPoint.getY() > this.m_CropBotRight.getY())
                && (paramPoint.getY() <= this.m_Canvas.getHeight()))
            this.m_CropBotRight.setY(paramPoint.getY());
        this.m_Points.add(paramPoint);
        drawPoints();
    }

    // public void clear() {
    // if (this.m_Canvas == null)
    // this.m_Canvas.drawColor(0, PorterDuff.Mode.CLEAR);
    // invalidate();
    // // return;
    // }

    public void clear() {
        if (this.m_Canvas == null)
            return;
        while (m_Empty) {
            m_Canvas.drawColor(0, PorterDuff.Mode.CLEAR);
            m_Empty = true;
            invalidate();
            return;
        }
    }

    public void drawBitmap(Bitmap paramBitmap) {
        clear();
        if ((paramBitmap != null) && (this.m_Canvas != null)
                && (this.m_Canvas.getWidth() != 0)
                && (this.m_Canvas.getHeight() != 0)) {
            Matrix localMatrix = new Matrix();
            localMatrix.setRectToRect(
                    new RectF(0.0F, 0.0F, paramBitmap.getWidth(), paramBitmap
                            .getHeight()),
                    new RectF(0.0F, 0.0F, this.m_Canvas.getWidth(),
                            this.m_Canvas.getHeight()),
                    Matrix.ScaleToFit.CENTER);
            this.m_Canvas.drawBitmap(paramBitmap, localMatrix, null);
            m_Empty = false;
        }
        invalidate();
    }

    public void drawPoints() {
        if ((m_Points.size() >= 4)
                && (4 + this.m_PointIndex <= this.m_Points.size())) {
            Point localPoint1 = (Point) this.m_Points.get(this.m_PointIndex);
            Point localPoint2 = (Point) this.m_Points
                    .get(1 + this.m_PointIndex);
            Point localPoint3 = (Point) this.m_Points
                    .get(2 + this.m_PointIndex);
            Point localPoint4 = (Point) this.m_Points
                    .get(3 + this.m_PointIndex);
            Bezier localBezier = new Bezier(localPoint1, localPoint2,
                    localPoint3, localPoint4);
            localBezier.setColor(Color.GREEN);
            float f = strokeWidth(8.0F / localPoint4.velocityFrom(localPoint1));
            addBezier(localBezier, this.m_LastWidth, f);
            invalidate();
            this.m_LastWidth = f;
            this.m_PointIndex = (3 + this.m_PointIndex);
            m_Empty = false;
        }
    }

    public boolean isEmpty() {
        return m_Empty;
    }

    public Bitmap getBitmap() {
        return this.m_Bitmap;
    }

    public int getColor() {
        return this.color;
    }

    protected void onDraw(Canvas paramCanvas) {
        if (this.m_Bitmap != null)
            paramCanvas.drawBitmap(this.m_Bitmap, 0.0F, 0.0F, null);
    }

    protected void onMeasure(int paramInt1, int paramInt2) {
        int i = View.MeasureSpec.getSize(paramInt1);
        int j = View.MeasureSpec.getSize(paramInt2);
        this.m_CropTopLeft = new Point(i, j);
        this.m_CropBotRight = new Point(0.0F, 0.0F);
        setMeasuredDimension(i, j);
    }

    protected void onSizeChanged(int paramInt1, int paramInt2, int paramInt3,
            int paramInt4) {
        Bitmap localBitmap = Bitmap.createBitmap(paramInt1, paramInt2,
                Bitmap.Config.ARGB_8888);
        this.m_Canvas = new Canvas(localBitmap);
        float f1 = 2.0F * (this.m_Canvas.getWidth() + this.m_Canvas.getHeight() - 2.0F * this.m_StrokeWidth);
        float f2 = f1
                * this.m_DesiredDash
                / (Math.round(f1 / (4.0F * this.m_DesiredDash)) * (4.0F * this.m_DesiredDash));
        Paint localPaint = this.m_BorderPaint;
        float[] arrayOfFloat = new float[2];
        arrayOfFloat[0] = f2;
        arrayOfFloat[1] = f2;
        localPaint.setPathEffect(new DashPathEffect(arrayOfFloat, f2 / 2.0F));
        clear();
        if (this.m_Bitmap != null) {
            Rect localRect = new Rect(0, 0, this.m_Canvas.getWidth(),
                    this.m_Canvas.getHeight());
            this.m_Canvas.drawBitmap(this.m_Bitmap, null, localRect, null);
            m_Empty = false;
        }
        this.m_Bitmap = localBitmap;
    }

    public boolean onTouchEvent(MotionEvent paramMotionEvent) {
        int i = 0xFF & paramMotionEvent.getAction();
        if (i == 0) {
            this.m_CurrentX = paramMotionEvent.getX();
            this.m_CurrentY = paramMotionEvent.getY();
            addPoint(new Point(this.m_CurrentX, this.m_CurrentY,
                    paramMotionEvent.getEventTime()));
            getParent().requestDisallowInterceptTouchEvent(true);
        }
        // while (m_Empty) {
        if ((i == 1) || (i == 3)) {
            this.m_CurrentY = (0.0F / 0.0F);
            this.m_CurrentX = (0.0F / 0.0F);
            this.m_Points.clear();
            this.m_PointIndex = 0;
            getParent().requestDisallowInterceptTouchEvent(false);
        }
        // if ((this.m_Points.size() < 4) || (4 + this.m_PointIndex >
        // this.m_Points.size()))
        // while (1 + this.m_PointIndex <= this.m_Points.size())
        drawPoints();
        if ((i == 2) || (i == 1)) {
            for (int j = 0; j < paramMotionEvent.getHistorySize(); j++)
                addPoint(new Point(paramMotionEvent.getHistoricalX(j),
                        paramMotionEvent.getHistoricalY(j),
                        paramMotionEvent.getHistoricalEventTime(j)));
            addPoint(new Point(paramMotionEvent.getX(),
                    paramMotionEvent.getY(), paramMotionEvent.getEventTime()));

        }
        // }
        return true;
    }

    public void setColor(int paramInt) {
        this.color = Color.BLACK;
    }

    public Point getCropBotRight() {
        return this.m_CropBotRight;
    }

    public Point getCropTopLeft() {
        return this.m_CropTopLeft;
    }

    // public float strokeWidth(float paramFloat) {
    // if (paramFloat > 11.0F)
    // paramFloat = 10.0F;
    // if (paramFloat < 5.0F)
    // paramFloat = 6.0F;
    // return paramFloat;
    // }

    public float strokeWidth(float paramFloat) {
        if (paramFloat > 11.0F)
            paramFloat = 10.0F;
        while (m_Empty) {
            if (paramFloat < 5.0F)
                paramFloat = 6.0F;
            return paramFloat;
        }
        return paramFloat;
    }

}

点.java

    private long time;
    private float x;
    private float y;

    public Point(float paramFloat1, float paramFloat2) {
        this.x = paramFloat1;
        this.y = paramFloat2;
    }

    public Point(float paramFloat1, float paramFloat2, long paramLong) {
        this.x = paramFloat1;
        this.y = paramFloat2;
        this.time = paramLong;
    }

    protected float distanceTo(Point paramPoint) {
        float f1 = this.x - paramPoint.getX();
        float f2 = this.y - paramPoint.getY();
        return FloatMath.sqrt(f1 * f1 + f2 * f2);
    }

    public long getTime() {
        return this.time;
    }

    public float getX() {
        return this.x;
    }

    public float getY() {
        return this.y;
    }

    public void setX(float paramFloat) {
        this.x = paramFloat;
    }

    public void setY(float paramFloat) {
        this.y = paramFloat;
    }

    public float velocityFrom(Point paramPoint) {
            return distanceTo(paramPoint) / (this.time - paramPoint.time);
    }
}

贝塞尔.java

public class Bezier {
private Point controlPointOne;
private Point controlPointTwo;
private int drawSteps;
private Point endPoint;
private int mColor;
private Point startPoint;

public Bezier() {
}

public Bezier(Point paramPoint1, Point paramPoint2, Point paramPoint3,
        Point paramPoint4) {
    this.startPoint = paramPoint1;
    this.controlPointOne = paramPoint2;
    this.controlPointTwo = paramPoint3;
    this.endPoint = paramPoint4;
    this.drawSteps = ((int) (paramPoint1.distanceTo(paramPoint2)
            + paramPoint2.distanceTo(paramPoint3) + paramPoint3
            .distanceTo(paramPoint4)));
}

public void draw(Canvas paramCanvas, Paint paramPaint, float paramFloat1,
        float paramFloat2) {
    float f1 = paramFloat2 - paramFloat1;
    for (int i = 0; i < this.drawSteps; i++) {
        float f2 = i / this.drawSteps;
        float f3 = f2 * f2;
        float f4 = f3 * f2;
        float f5 = 1.0F - f2;
        float f6 = f5 * f5;
        float f7 = f6 * f5;
        float f8 = f7 * this.startPoint.getX() + f2 * (3.0F * f6)
                * this.controlPointOne.getX() + f3 * (3.0F * f5)
                * this.controlPointTwo.getX() + f4 * this.endPoint.getX();
        float f9 = f7 * this.startPoint.getY() + f2 * (3.0F * f6)
                * this.controlPointOne.getY() + f3 * (3.0F * f5)
                * this.controlPointTwo.getY() + f4 * this.endPoint.getY();
        paramPaint.setColor(getColor());
        paramPaint.setStrokeWidth(paramFloat1 + f4 * f1);
        paramCanvas.drawPoint(f8, f9, paramPaint);
    }
}

public int getColor() {
    return this.mColor;
}

public Point getControlPointOne() {
    return this.controlPointOne;
}

public Point getControlPointTwo() {
    return this.controlPointTwo;
}

public int getDrawSteps() {
    return this.drawSteps;
}

public Point getEndPoint() {
    return this.endPoint;
}

public Point getStartPoint() {
    return this.startPoint;
}

public void setColor(int paramInt) {
    this.mColor = Color.BLACK;
}

public void setControlPointOne(Point paramPoint) {
    this.controlPointOne = paramPoint;
}

public void setControlPointTwo(Point paramPoint) {
    this.controlPointTwo = paramPoint;
}

public void setDrawSteps(int paramInt) {
    this.drawSteps = paramInt;
}

public void setEndPoint(Point paramPoint) {
    this.endPoint = paramPoint;
}

public void setStartPoint(Point paramPoint) {
    this.startPoint = paramPoint;
}

}


答案 1

将贝塞尔类中的绘制方法更改为：

public void draw(Canvas canvas, Paint paint, float startWidth, float endWidth) {
    float originalWidth = paint.getStrokeWidth();
    float widthDelta = endWidth - startWidth;

    for (int i = 0; i < drawSteps; i++) {
        float t = ((float) i) / drawSteps;
        float tt = t * t;
        float ttt = tt * t;
        float u = 1 - t;
        float uu = u * u;
        float uuu = uu * u;

        float x = uuu * startPoint.x;
        x += 3 * uu * t * getControlPointOne().x;
        x += 3 * u * tt * getControlPointTwo().x;
        x += ttt * endPoint.x;

        float y = uuu * startPoint.y;
        y += 3 * uu * t * getControlPointOne().y;
        y += 3 * u * tt * getControlPointTwo().y;
        y += ttt * endPoint.y;

        paint.setStrokeWidth(startWidth + ttt * widthDelta);
        canvas.drawPoint(x, y, paint);
    }

    paint.setStrokeWidth(originalWidth);
}

答案 2

您需要查看在贝塞尔类中绘制了多少点并将它们相加。

从你的代码中：你正在收集4个点，并在它们上面画一条贝塞尔曲线。这意味着该算法 - 根据设计 - 将错过一半的采样点。

其他选项：1.创建自己的贝塞尔曲线或低阶（例如 - 阶3） - 然后您只会错过1/3的点。这有点使问题变得毫无用处，因为您希望保存的数据少于采样的数据。2. 创建一条高阶贝塞尔曲线，可以近似整个签名。

但是，您可以尝试找出要选择的点，以获得更接近签名的贝塞尔曲线：选择字母“l”的顶部作为一条贝塞尔曲线的终点，另一条曲线的起点将产生更好的结果。


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