在画布上绘图并保存图像 [英] Drawing on Canvas and save image

问题描述

我是 Android 图形类的新手.我想使用触摸事件绘制图像(实际上是一种签名类型)，并希望在我想保存时将其保存在 SD 卡上.我已经通过网络扫描任何此类教程，但我没有找到任何.谁能告诉我如何使用触摸事件在画布上绘制并保存它.

I am new to the Android Graphics class. I want to draw an image(actually a signature kind) using the touch events and want it to be saved on SDcard when I want to save it. I have scanned through the web for any such tutorials but I have not found any. Can anyone please tell me how to draw on canvas using the touch events and save it.

任何教程或示例代码都会有很大帮助.

Any tutorials or sample code will be of great help.

推荐答案

我在 android 开发人员上看到了非常好的代码，但我找不到了...它的输出是贝塞尔曲线，所以它会非常平滑.这是我编辑的代码:

I saw really good code on android developers, but I can't find it anymore... It's output is bezier curves so it will be pretty smooth. Here is code that I edited:

public class MyDrawView extends View {

private Bitmap  mBitmap;
private Canvas  mCanvas;
private Path    mPath;
private Paint   mBitmapPaint;
private Paint   mPaint;

public MyDrawView(Context c) {
    super(c);

    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(0xFF000000);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(3);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
}

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

@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;
}

public void clear(){
    mBitmap.eraseColor(Color.TRANSPARENT);
    invalidate();
    System.gc();
}}

然后在您想要使用它的活动的 onCreate 中，您只需编写如下内容:

then in onCreate of activity you want to use it in you just write something like this:

RelativeLayout parent = (RelativeLayout) findViewById(R.id.signImageParent);
myDrawView = new MyDrawView(this);
parent.addView(myDrawView);

这个视图是透明的，使用黑色颜料用手指绘制.所以如果你想看看你画的东西，只需在这个视图的背景上画一张白色或灰色的位图(你只需在 onDraw 的开始处添加一行)，或者你可以使用父级的背景.

This view is transparent and uses black paint to draw with your finger. So if you want see what you draw simply draw a white or gray bitmap on background of this view (you just add one line in the beginnig of onDraw), or you can use the background of the parent.

然后，当您想根据您绘制的内容创建图像时，只需调用

Then when you want to create an image from what you have drawn you just call

parent.setDrawingCacheEnabled(true);
Bitmap b = parent.getDrawingCache();

FileOutputStream fos = null;
try {
fos = new FileOutputStream(getFileName());
} catch (FileNotFoundException e) {
e.printStackTrace();
}

b.compress(CompressFormat.PNG, 95, fos);

这取决于您想要作为输出的内容，您可以使用此代码，也可以使用 myDrawView 代替 parent没有背景绘制(因为我们的 myDrawView 背景是透明的).

It depends on what you want to have as output, you can use this code or instead of parent you can do this with myDrawView and you get just the image you have drawn without background (since we have our myDrawView background transparent).

希望这会有所帮助.随时留下反馈.

Hope this will help. Feel free to leave feedback.

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