Question

假设我有2个位图。一个是smallBitmap，一个是largeBitmap。

我想将整个smallBitmap绘制到largeBitmap中，但只绘制到largeBitmap的一部分，而不是直接调整，而是改为quadrilateral。

我认为草图最能描述我的意思：

此方案的一个示例是倾斜的智能手机图像（如this或this），您需要将屏幕截图放入其屏幕。

输入是：smallBitmap，largeBitmap，largeBitmap的“四边形”坐标（放置smallBitmap的位置）。

largeBitmap的“四边形”只有4个坐标，不一定是矩形。例如，它可以是平行四边形或梯形。

我需要将smallBitmap缩放到largeBitmap中的四边形，并且还支持中心裁剪缩放，这样它就不会失真

我还需要知道如何以同样的方式处理文本，但我想这是关于相同的解决方案。

这是我尝试过的东西，但它甚至没有扩展：

    //mBigBitmap: size is 720x1280
    //mSmallBitmap: size is 720x720
    mLeftTop = new Point(370, 358);
    mRightTop = new Point(650, 384);
    mLeftBot = new Point(375, 972);
    mRightBot = new Point(660, 942);
    Canvas canvas = new Canvas(mBigBitmap);
    final Matrix matrix = new Matrix();
    matrix.setPolyToPoly(new float[]{0, 0,
                    mBigBitmap.getWidth() - 1, 0,
                    0, mBigBitmap.getHeight() - 1,
                    mBigBitmap.getWidth() - 1, mBigBitmap.getHeight() - 1},
            0,
            new float[]{mLeftTop.x, mLeftTop.y,
                    mRightTop.x, mRightTop.y,
                    mLeftBot.x, mLeftBot.y,
                    mRightBot.x, mRightBot.y
            }
            , 0, 4);
    canvas.drawBitmap(mSmallBitmap, matrix, new Paint());

Answer 1

倾斜位图，可能Matrix很方便。

   /*use values accordingly*/
   Matrix matrix = new Matrix();
   matrix.postScale(curScale, curScale);  
   matrix.postRotate(curRotate);
   matrix.postSkew(curSkewX, curSkewY);

   Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0, bmpWidth, bmpHeight, matrix, true);
   myImageView.setImageBitmap(resizedBitmap);

Answer 2

对于我的回答，我将较小的Bitmap绘制为较大的Bitmap，然后将其绘制到SurfaceView。

使用边界四边形创建边界矩形。
使用边界矩形创建转换Matrix
使用Matrix.ScaleToFit.CENTER将边界矩形填充为较小Bitmap的最大尺寸。

完成这些步骤后，只需绘制更大的Bitmap正在使用的画布。边界四边形绘制为红色，边界矩形为蓝色，大Bitmap绘制为绿色。将较小的Bitmap替换为蓝色Bitmap（边界矩形）。

public class MainActivity extends Activity {
final String TAG = this.getClass().getName();

SurfaceView surfaceView;
Bitmap bitmap;
Bitmap bigBitmap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    surfaceView = (SurfaceView) findViewById(R.id.surfaceView);
    surfaceView.getHolder().addCallback(new SurfaceHolder.Callback2() {
        @Override
        public void surfaceRedrawNeeded(SurfaceHolder holder) {

        }

        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            Canvas surfaceCanvas = holder.lockCanvas();

            surfaceCanvas.drawBitmap(bigBitmap, 0, 0, new Paint());

            holder.unlockCanvasAndPost(surfaceCanvas);
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {

        }
    });

    bitmap = Bitmap.createBitmap(64, 192, Bitmap.Config.ARGB_8888);
    {
        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint();
        paint.setColor(Color.RED);
        canvas.drawRect(0, 0, 64, 192, paint);
    }

    bigBitmap = Bitmap.createBitmap(768,768, Bitmap.Config.ARGB_8888);
    {
        Canvas canvas = new Canvas(bigBitmap);

        // Fill background - For visual reference
        Paint paint = new Paint();
        paint.setColor(Color.GREEN);
        canvas.drawRect(0, 0, bigBitmap.getWidth(), bigBitmap.getHeight(), paint);

        // Setup transformation
        Matrix matrixPoly = new Matrix();
        Log.i(TAG, "matrixPoly: " + matrixPoly);

        // Draw Quadrilateral - For visual reference
        boolean canScale;
        canScale = matrixPoly.setPolyToPoly(new float[]{0,0, 64,0, 0,192, 64,192},
                0,
                new float[]{32,32, 96,16, 16,300, 128,256},
                0,
                4);

        Log.i(TAG, "matrixPoly: " + matrixPoly);
        Log.i(TAG, "matrixPoly canScale: " + canScale);

        canvas.drawBitmap(bitmap, matrixPoly, new Paint());

        // Points of Quadrilateral
        // {32,32, 96,16, 16,300, 128,256}
        float rectInQLeft = Math.max(32, 16);
        float rectInQTop = Math.min(32, 16);
        float rectInQRight = Math.min(96, 128);
        float rectInQBottom = Math.max(300, 256);
        ;
        Matrix matrixRect = new Matrix();
        Log.i(TAG, "matrixRect: " + matrixRect);
        canScale = matrixRect.setRectToRect(new RectF(0, 0, 64, 192),
                new RectF(rectInQLeft, rectInQTop, rectInQRight, rectInQBottom),
                Matrix.ScaleToFit.CENTER);

        Log.i(TAG, "matrixRect: " + matrixRect);
        Log.i(TAG, "matrixRect canScale: " + canScale);

        // Draw scaled bitmap
        Canvas smallBitmapCanvas = new Canvas(bitmap);
        Paint smallBitmapPaint = new Paint();
        smallBitmapPaint.setColor(Color.BLUE);
        smallBitmapCanvas.drawRect(0, 0, 64, 192, smallBitmapPaint);

        canvas.drawBitmap(bitmap, matrixRect, new Paint());
    }
}

如何将位图绘制到另一个，但进入给定的四边形（不必是矩形）？

2 个答案: