自定义控件：手势缩放移动，遮罩

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PointF;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

import com.lhcm.print.imageprinter.R;

/**
 * Created by chenweiqi on 2017/1/12.
 */

public class TouchView extends View {

    float x_down = 0;
    float y_down = 0;
    PointF start = new PointF();
    PointF mid = new PointF();
    float oldDist = 1f;
    float oldRotation = 0;
    Matrix matrix = new Matrix();
    Matrix matrix1 = new Matrix();
    Matrix savedMatrix = new Matrix();
    Matrix desMatrix ;

    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    int mode = NONE;

    boolean matrixCheck = false;

    int widthScreen;
    int heightScreen;

    Bitmap source;

    Bitmap des;

    Rect borderRect;

    boolean isNeedPaintBorder = false;
    boolean isNeedPaintText = false;
    Paint borderPaint;

    String paintText = "相片超出边界";

    int viewHeight;
    int viewWidth;
    Paint paint;

    boolean doOnDraw = false;

    boolean touchAble = true;

    public TouchView(Context context) {
        this(context,null);

    }

    public TouchView(Context context, AttributeSet attrs) {
        super(context, attrs);
        source = BitmapFactory.decodeResource(getResources(), R.mipmap.test2);

        DisplayMetrics dm = new DisplayMetrics();
        ((WindowManager) context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getMetrics(dm);
        widthScreen = dm.widthPixels;
        heightScreen = dm.heightPixels;

        matrix = new Matrix();
        des = BitmapFactory.decodeResource(getResources(), R.mipmap.star);

        borderPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        borderPaint.setColor(Color.RED);
        borderPaint.setStyle(Paint.Style.STROKE);
        borderPaint.setStrokeWidth(3);

        borderRect = new Rect();

        paint = new Paint();
        paint.setAntiAlias(true);
    }

    protected void onDraw(Canvas canvas) {
        viewHeight = getHeight();
        viewWidth = getWidth();
        paint.setAntiAlias(true);

        canvas.save();
        int saveLayerCount = canvas.saveLayer(0, 0, viewWidth, viewHeight, paint, Canvas.ALL_SAVE_FLAG);
        if(source!=null) {
            canvas.drawBitmap(source, matrix, null);
        }

        if (des!=null) {
            if (desMatrix == null) {
                desMatrix = new Matrix();
                desMatrix.setScale(viewWidth * 1f / des.getWidth(), viewHeight * 1f / des.getHeight());
            }
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
            canvas.drawBitmap(des, desMatrix, paint);
            paint.setXfermode(null);
        }

        if (isNeedPaintBorder){
            paintViewBorder(canvas);
        }
        if (isNeedPaintText) {
            paintText(canvas);
        }
        canvas.restoreToCount(saveLayerCount);
        canvas.restore();
        doOnDraw = true;
        System.gc();
    }

    public boolean onTouchEvent(MotionEvent event) {
        doOnDraw = false;
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                isNeedPaintBorder = true;
                mode = DRAG;
                x_down = event.getX();
                y_down = event.getY();
                savedMatrix.set(matrix);
                invalidate();
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                mode = ZOOM;
                oldDist = spacing(event);
                oldRotation = rotation(event);
                savedMatrix.set(matrix);
                midPoint(mid, event);
                break;
            case MotionEvent.ACTION_MOVE:
                if (mode == ZOOM) {
                    matrix1.set(savedMatrix);
                    float rotation = rotation(event) - oldRotation;
                    float newDist = spacing(event);
                    float scale = newDist / oldDist;
                    matrix1.postScale(scale, scale, mid.x, mid.y);// 縮放
                    matrix1.postRotate(rotation, mid.x, mid.y);// 旋轉
                    matrixCheck = matrixCheck();
                    if (matrixCheck == false) {
                        matrix.set(matrix1);
                        invalidate();
                    }
                } else if (mode == DRAG) {
                    matrix1.set(savedMatrix);
                    matrix1.postTranslate(event.getX() - x_down, event.getY()- y_down);// 平移
                    if (!matrixCheck()) {
                        matrix.set(matrix1);
                        invalidate();
                    }
                }
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP:
                mode = NONE;
                isNeedPaintBorder = false;
                invalidate();
                break;
        }
        return touchAble;
    }

    private boolean matrixCheck() {
        float[] f = new float[9];
        matrix1.getValues(f);
        // 图片4个顶点的坐标
        float x1 = f[0] * 0 + f[1] * 0 + f[2];
        float y1 = f[3] * 0 + f[4] * 0 + f[5];
        float x2 = f[0] * source.getWidth() + f[1] * 0 + f[2];
        float y2 = f[3] * source.getWidth() + f[4] * 0 + f[5];
        float x3 = f[0] * 0 + f[1] * source.getHeight() + f[2];
        float y3 = f[3] * 0 + f[4] * source.getHeight() + f[5];
        float x4 = f[0] * source.getWidth() + f[1] * source.getHeight() + f[2];
        float y4 = f[3] * source.getWidth() + f[4] * source.getHeight() + f[5];
        // 图片现宽度
        double width = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
        // 缩放比率判断
        if (width < viewWidth / 3 || width > viewHeight * 3) {
            return true;
        }

        // 出界判断
        int ds= 3;
        if ((y1>viewHeight+ds&&y2>viewHeight+ds&&y3>viewHeight+ds&&y4>viewHeight+ds)
                ||(y1<-ds&&y2<-ds&&y3<-ds&&y4<-ds)
                ||(x1>viewWidth+ds&&x2>viewWidth+ds&&x3>viewWidth+ds&&x4>viewWidth+ds)
                ||(x1<-ds&&x2<-ds&&x3<-ds&&x4<-ds)){
            isNeedPaintText = true;
            return true;
        }else {
            isNeedPaintText = false;
        }
        return false;
    }

    // 触碰两点间距离
    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    // 取手势中心点
    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    // 取旋转角度
    private float rotation(MotionEvent event) {
        double delta_x = (event.getX(0) - event.getX(1));
        double delta_y = (event.getY(0) - event.getY(1));
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }

    // 将移动，缩放以及旋转后的图层保存为新图片
    public Bitmap creatNewPhoto() {
        Bitmap bitmap = Bitmap.createBitmap(widthScreen, heightScreen,
                Bitmap.Config.ARGB_8888); // 背景图片
        Canvas canvas = new Canvas(bitmap); // 新建画布
        canvas.drawBitmap(source, matrix, null); // 画图片
        canvas.save(Canvas.ALL_SAVE_FLAG); // 保存画布
        canvas.restore();
        return bitmap;
    }

   //画边界
    private void paintViewBorder(Canvas canvas){
        getLocalVisibleRect(borderRect);
        borderRect.top+=3;
        borderRect.bottom-=3;
        borderRect.left+=3;
        borderRect.right-=3;
        canvas.drawRect(borderRect,borderPaint);
    }

    private void paintText(Canvas canvas){
        Paint textPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        textPaint.setTextSize(35);
        textPaint.setColor(Color.RED);
        Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
        Rect textRect = new Rect();
        textPaint.getTextBounds(paintText,0,paintText.length(),textRect);

        int x = (viewWidth-textRect.right+textRect.left)/2;
        int y = (int) ((viewHeight*1f-textRect.bottom+textRect.top)/2+(fontMetrics.bottom-fontMetrics.top)/2);
        canvas.drawText(paintText, x, y, textPaint);
    }

    @Override
    public Matrix getMatrix() {
        return matrix;
    }

    public void setMatrix(Matrix matrix) {
        this.matrix = matrix;
        invalidate();
    }

    @Override
    public void invalidate() {
        super.invalidate();
        if (!doOnDraw) {
            ((View) getParent()).invalidate();
        }
    }

    public void setSourceBitmap(Bitmap source){
        this.source = source;
    }
    public void setDesBitmap(Bitmap des){
        this.des = des;
    }

    public void setTouchAble(boolean touchAble){
        this.touchAble = touchAble;
    }
}