我正在制作一个应用程序，我最近 3 天无法尽可能多地使用谷歌。我在 Canvas 上画了一个圆圈，想裁剪该部分的图像并以缩放模式显示该图像。我的第一步就像屏幕在这里:-

在此我选择区域。这是我为此使用的代码。

private float x, y;
private boolean zooming = false;
private Paint mPaint;
private Matrix mmatrix;
private Shader mShader;
private Bitmap mBitmap;
private  List<Point> mpoints;
private List<MyPoints> mpointlist;
private Path mpath;
private Canvas mcanvas;
private Bitmap mresult_bitmap, resultingImage,finalbitmap;
private Context mcontext;
private boolean bfirstpoint = false;
private Point mfirstpoint = null;
private Point mlastpoint = null;

public CircularZoomView(Context context) {
    super(context);
    mcontext = context;
    mpath = new Path();
    mpoints = new ArrayList<Point>();
    setBackgroundResource(R.drawable.testing);
    mPaint = new Paint();

    mresult_bitmap = BitmapFactory.decodeResource(getResources(),
     R.drawable.testing);

    mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setPathEffect(new DashPathEffect(new float[] { 10, 20 }, 0));
    mPaint.setStrokeWidth(5);
    mPaint.setColor(Color.RED);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (zooming && resultingImage!=null) {
        zooming = false;
        ShowImage(resultingImage);
        canvas.drawBitmap(resultingImage,mmatrix, null);
    }
    boolean first = true;

    for (int i = 0; i < mpoints.size(); i += 2) {
        Point point = mpoints.get(i);
        if (first) {
            first = false;
            mpath.moveTo(point.x, point.y);
        } else if (i < mpoints.size() - 1) {
            Point next = mpoints.get(i + 1);
            mpath.quadTo(point.x, point.y, next.x, next.y);
        } else {
            mlastpoint = mpoints.get(i);
            mpath.lineTo(point.x, point.y);
        }
    }

    canvas.drawPath(mpath, mPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {

    int action = event.getAction();

    x = event.getX();
    y = event.getY();

    Point point = new Point();
    point.x = (int) event.getX();
    point.y = (int) event.getY();

    if (bfirstpoint) {
        if (comparepoint(mfirstpoint, point)) {
            mpoints.add(mfirstpoint);
            addCircleFromPath(mpath);
        } else {
            mpoints.add(point);
        }
    } else {
        mpoints.add(point);
    }

    if (!(bfirstpoint)) {
        mfirstpoint = point;
        bfirstpoint = true;
    }

    invalidate();

    switch (action) {
    case MotionEvent.ACTION_DOWN:
    case MotionEvent.ACTION_MOVE:

        zooming = false;
        this.invalidate();
        break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_CANCEL:
        zooming = true;
        mlastpoint = point;
            if (mpoints.size() > 12) {
                if (!comparepoint(mfirstpoint, mlastpoint)) {
                    mpoints.add(mfirstpoint);
                    addCircleFromPath(mpath);
                }
            }
        this.invalidate();
        break;

    default:
        break;
    }

    return true;
}


public Bitmap getCroppedBitmap(Bitmap bitmap) {

    Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
            bitmap.getHeight(), Config.ARGB_8888);
    Canvas canvas = new Canvas(output);

    final int color = 0xff424242;
    final Paint paint = new Paint();
    final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());

    paint.setAntiAlias(true);
    canvas.drawARGB(0, 0, 0, 0);
    paint.setColor(color);
    canvas.drawCircle(bitmap.getWidth() / 2, bitmap.getHeight() / 2,
            bitmap.getWidth() / 2, paint);
    paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
    canvas.drawBitmap(bitmap, rect, rect, paint);
    return output;
}



void ShowImage(Bitmap mbitmap) {
    Display display = ((MainActivity) mcontext).getWindowManager().getDefaultDisplay(); 
    int screenWidth = display.getWidth();
    float imageWidth = (float)mbitmap.getWidth();
    float imageHeight = (float)mbitmap.getHeight();
    float newHeight = imageHeight / (imageWidth / screenWidth);
    float newWidth = screenWidth;
    float scaleWidth = screenWidth / imageWidth;
    float scaleHeight = newHeight / imageHeight;
    SetImageMatrix(mbitmap,scaleWidth,scaleHeight);

    }

void SetImageMatrix(Bitmap image,float scaleWidth, float scaleHeight) {
    mmatrix = new Matrix();
    mmatrix.setTranslate(40,40);
    mmatrix.postScale(scaleWidth/2, scaleHeight/2);
    /*image.setImageMatrix(mmatrix);
    image.setScaleType(ScaleType.MATRIX);
    image.invalidate();*/

    }

private boolean comparepoint(Point first, Point current) {
    int left_range_x = (int) (current.x - 3);
    int left_range_y = (int) (current.y - 3);

    int right_range_x = (int) (current.x + 3);
    int right_range_y = (int) (current.y + 3);


    if ((left_range_x < first.x && first.x < right_range_x)
            && (left_range_y < first.y && first.y < right_range_y)) {
        if (mpoints.size() < 10) {
            return false;
        } else {
            return true;
        }
    } else {
        return false;
    }

}

private void addCircleFromPath(Path path){
    RectF bounds = new RectF();
    path.computeBounds(bounds, true);
    int width = (int) (bounds.right-bounds.left);
    int height = (int) (bounds.bottom-bounds.top);
    if(width<20 && height<20){
        path.reset();
        return;
    }
    int radius  ; 
    if(width>=height)
        radius = Math.round(((width/2))); 
    else radius = Math.round((int) ((height/2)));
    /*CircleTagObject circle = new CircleTagObject((int)bounds.left+width/2, (int)bounds.top+height/2, radius, crossBitmap, tagBitmap,circleArray.size(),
            ImageEditorView.this);
    circleArray.add(circle);
    tagBallID = circleArray.size() - 1;
    dragEnable = true;*/

    resultingImage = getCroppedBitmap(Bitmap.createBitmap(mresult_bitmap,0,0,200,200));
    mcanvas = new Canvas(resultingImage);
    path.reset();
    resetView();
    invalidate();
}

public void resetView() {
    mpoints.clear();
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setPathEffect(new DashPathEffect(new float[] { 10, 20 }, 0));
    mPaint.setStrokeWidth(5);
    mPaint.setColor(Color.RED);
    invalidate();
}

如果我像上面那样创建硬编码位图，它会显示良好但不是所选部分的裁剪位图。就像这张图片。

但是当添加选定区域的精确坐标时，如:-

resultingImage = getCroppedBitmap(Bitmap.createBitmap(mresult_bitmap,(int)bounds.left,(int)bounds.top,width,height));

然后发生异常:-

 07-12 10:58:56.700: E/MessageQueue-JNI(12310): java.lang.IllegalArgumentException: y + height must be <= bitmap.height()
07-12 10:58:56.700: E/MessageQueue-JNI(12310):  at android.graphics.Bitmap.createBitmap(Bitmap.java:565)
07-12 10:58:56.700: E/MessageQueue-JNI(12310):  at android.graphics.Bitmap.createBitmap(Bitmap.java:530)
07-12 10:58:56.700: E/MessageQueue-JNI(12310):  at com.intel.view.CircularZoomView.addCircleFromPath(CircularZoomView.java:237)

我知道为什么会出现此异常，但无法找到如何裁剪所选部分图像的解决方案。在此先感谢。

最佳答案

我知道您的解决方案为时已晚，但这可能对其他人有帮助 Use of this code 帮助您摆脱这个问题。

关于android - 如何在 Canvas 上裁剪选定区域的位图？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/17607999/