android自定义图片裁剪

Android中自定义图片裁剪可以通过使用自定义View和Bitmap对象来实现。以下是一些步骤：

1. 创建自定义View类，继承自View类。在onDraw()方法中绘制Bitmap对象。

2. 设置触摸事件，获取用户手指操作的坐标，计算出裁剪区域的左上角和右下角坐标。

3. 在onTouchEvent()方法中重绘View，绘制裁剪后的Bitmap对象。

4. 使用Matrix对象进行缩放和旋转操作。

下面是一个简单的示例代码：

public class CropImageView extends View {
    private Bitmap mBitmap;
    private Paint mPaint;
    private Rect mRect;
    private Matrix mMatrix;

    private float mStartX;
    private float mStartY;
    private float mEndX;
    private float mEndY;

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

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

    private void init() {
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(5);
        mPaint.setColor(Color.RED);

        mRect = new Rect();
        mMatrix = new Matrix();
    }

    public void setImageBitmap(Bitmap bitmap) {
        mBitmap = bitmap;
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        if (mBitmap != null) {
            canvas.drawBitmap(mBitmap, mMatrix, null);
        }

        canvas.drawRect(mRect, mPaint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mStartX = event.getX();
                mStartY = event.getY();
                mEndX = mStartX;
                mEndY = mStartY;
                break;

            case MotionEvent.ACTION_MOVE:
                mEndX = event.getX();
                mEndY = event.getY();
                break;

            case MotionEvent.ACTION_UP:
                mEndX = event.getX();
                mEndY = event.getY();
                break;
        }

        calculateRect();

        invalidate();
        return true;
    }

    private void calculateRect() {
        float left = Math.min(mStartX, mEndX);
        float top = Math.min(mStartY, mEndY);
        float right = Math.max(mStartX, mEndX);
        float bottom = Math.max(mStartY, mEndY);

        mRect.set((int) left, (int) top, (int) right, (int) bottom);

        float centerX = (left + right) / 2;
        float centerY = (top + bottom) / 2;

        mMatrix.reset();
        mMatrix.postTranslate(-centerX, -centerY);
        mMatrix.postRotate(45);
        mMatrix.postScale(0.5f, 0.5f);
        mMatrix.postTranslate(centerX, centerY);
    }
}

这个示例代码实现了一个简单的图片裁剪功能，并在裁剪后对图片进行了缩放和旋转。你可以根据自己的需求修改代码。