Android: digital signature using Bezier

Question

I am trying two draw digital signature using Bezier as show in above image.when i touch and try to draw line then the result is dot line but not getting continuous line. Simple signature done by using simple signature but I want to create more a smooth curve using Bezier with touch pressure. tried with this link

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;
    }

}

Point.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);
    }
}

Bezier.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;
}

}

Answer 1

Change draw method in Bezier class to:

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);
}

Answer 2

You need to see how many points are drawn in Bezier class and add them up.

From your code: You are collecting 4 points and draw a Bezier curve over them. This means that the algorithm - by design - will miss half of the sampled points.

Other options: 1. Create your own Bezier curve or lower order (say - order 3) - and then you'll miss only 1/3 of the points. This kinda renders the issue useless, as you want to conserve less data than sampled. 2. Create a high order Bezier curve that can approximate the whole signature.

You can, however, try to figure out what points you would like to select in order to get a Bezier curve which is closer to the signature : select the top of the letter 'l' as an end point of one Bezier curve and the start of another will yield better results.

Answer 3

You can use simple

code

public class MySignatureView extends View

 {

private Path mPath;

private Paint mPaint;
private Bitmap mBitmap;
private Canvas mCanvas;
private int bgColor;

private float curX, curY;
private boolean isDragged = false;

private static final int TOUCH_TOLERANCE = 4;
private static final int STROKE_WIDTH = 2;

public MySignatureView(Context context) {
    super(context);
    init();
}

public MySignatureView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
}

public MySignatureView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init();
}

private void init() {
    setFocusable(true);
    bgColor = Color.WHITE;
    mPath = new Path();
    mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaint.setColor(bgColor ^ 0x00FFFFFF);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeWidth(STROKE_WIDTH);
}

public void setSigColor(int color) {
    mPaint.setColor(color);
}

public void setSigColor(int a, int r, int g, int b) {
    mPaint.setARGB(a, r, g, b);
}

public void clearSig() {
    if (mCanvas != null) {
        mCanvas.drawColor(bgColor);
        mCanvas.drawPaint(mPaint);
        mPath.reset();
        invalidate();
    }
}

public Bitmap getImage() {
    return this.mBitmap;
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    int bitW = mBitmap != null ? mBitmap.getWidth() : 0;
    int bitH = mBitmap != null ? mBitmap.getWidth() : 0;

    if (bitW >= w && bitH >= h) {
        return;
    }

    if (bitW < w)
        bitW = w;
    if (bitH < h)
        bitH = h;

    Bitmap newBitmap = Bitmap.createBitmap(bitW, bitH,
            Bitmap.Config.ARGB_8888);
    Canvas newCanvas = new Canvas();
    newCanvas.setBitmap(newBitmap);

    if (mBitmap != null) {
        newCanvas.drawBitmap(mBitmap, 0, 0, null);
    }

    mBitmap = newBitmap;
    mCanvas = newCanvas;
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, mPaint);
    canvas.drawPath(mPath, mPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        touchDown(x, y);
        break;
    case MotionEvent.ACTION_MOVE:
        touchMove(x, y);
        break;
    case MotionEvent.ACTION_UP:
        touchUp();
        break;
    }
    invalidate();
    return true;
}

private void touchDown(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    curX = x;
    curY = y;
    isDragged = false;
}

private void touchMove(float x, float y) {
    float dx = Math.abs(x - curX);
    float dy = Math.abs(y - curY);
    if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
        mPath.quadTo(curX, curY, (x + curX) / 2, (y + curY) / 2);
        curX = x;
        curY = y;
        isDragged = true;
    }
}

private void touchUp() {
    if (isDragged) {
        mPath.lineTo(curX, curY);
    } else {
        mPath.lineTo(curX+2, curY+2);
    }
    mCanvas.drawPath(mPath, mPaint);
    mPath.reset();
}

  }