digital signature in android

Question

I want to create Digital signature application in android. It should capture user signature and store it as an image. If anybody know please let me know.

Answer 1

Try a custom view instead of gestures:

package com.example.myapp.gui.views;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

/**
 * A simple view to capture a path traced onto the screen. Initially intended to be used to captures signatures.
 * 
 * @author Andrew Crichton
 * @version 0.1
 */
public class SignatureView extends View {
    private Path mPath;
    private Paint mPaint; 
    private Paint bgPaint = new Paint(Color.TRANSPARENT);

    private Bitmap mBitmap;
    private Canvas mCanvas;

    private float curX, curY;

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

    public SignatureView(Context context) {
        super(context);
        init();
    }
    public SignatureView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    public SignatureView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }
    private void init() {
        setFocusable(true);
        mPath = new Path();
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(Color.WHITE);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(STROKE_WIDTH);
    }
    public void setSigColor(int color) {
        mPaint.setColor(color);
    }
    public void setSigColor(int a, int red, int green, int blue) {
        mPaint.setARGB(a, red, green, blue);
    }
    public boolean clearSignature() {
        if (mBitmap != null)
            createFakeMotionEvents();
        if (mCanvas != null) {
            mCanvas.drawColor(Color.BLACK);
            mCanvas.drawPaint(bgPaint);
            mPath.reset();
            invalidate();
        }
        else {
            return false;
        }
        return true;
    }
    public Bitmap getImage() {
        return this.mBitmap;
    }
    public void setImage(Bitmap bitmap) {
        this.mBitmap = bitmap;
        this.invalidate();
    }
    @Override
    protected void onSizeChanged(int width, int height, int oldWidth, int oldHeight) {
        int bitmapWidth = mBitmap != null ? mBitmap.getWidth() : 0;
        int bitmapHeight = mBitmap != null ? mBitmap.getWidth() : 0;
        if (bitmapWidth >= width && bitmapHeight >= height) 
            return;
        if (bitmapWidth < width) 
            bitmapWidth = width;
        if (bitmapHeight < height) 
            bitmapHeight = height;
        Bitmap newBitmap = Bitmap.createBitmap(bitmapWidth, bitmapHeight, Bitmap.Config.ARGB_8888);
        Canvas newCanvas = new Canvas();
        newCanvas.setBitmap(newBitmap);
        if (mBitmap != null) 
            newCanvas.drawBitmap(mBitmap, 0, 0, null);
        mBitmap = newBitmap;
        mCanvas = newCanvas;
    }
    private void createFakeMotionEvents() {
        MotionEvent downEvent = MotionEvent.obtain(SystemClock.uptimeMillis(),SystemClock.uptimeMillis()+100, MotionEvent.ACTION_DOWN, 1f, 1f ,0);
        MotionEvent upEvent = MotionEvent.obtain(SystemClock.uptimeMillis(),SystemClock.uptimeMillis()+100, MotionEvent.ACTION_UP, 1f, 1f ,0);
        onTouchEvent(downEvent);
        onTouchEvent(upEvent);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawColor(Color.BLACK);
        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 methods
     **---------------------------------------------------------*/

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

    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;
        }
    }

    private void touchUp() {
        mPath.lineTo(curX, curY);
        if (mCanvas == null) {
            mCanvas = new Canvas();
            mCanvas.setBitmap(mBitmap);
        }
        mCanvas.drawPath(mPath, mPaint);
        mPath.reset();
    }
}

Then, use this class in your XML: <com.example.myapp.gui.views.SignatureView .../> To get the drawn signature, use this: Bitmap bmp = ((SignatureView)findViewById(R.id.signatureview)).getImage();

You can eventually save the bitmap with this code:

public void saveBitmap(Bitmap bmp) {
    try {
        String root = Environment.getExternalStorageDirectory().getAbsolutePath() + "/";
        String filepath = root + "signature.jpg";

        FileOutputStream fos = new FileOutputStream(filepath);
        bmp.compress(CompressFormat.JPEG, 100, fos);
        fos.flush();
        fos.close();
    }
    catch(Exception e) {
        Log.e("Could not save", e.getMessage());
        e.printStackTrace();
    }
}

which will save the signature on the root of your sd card as signature.jpeg. For the writing part, make sure to have that permission in your manifest: <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>