In alcuni casi la distorsione di un'immagine in un quadrilatero non funziona su Android

Question

Sto utilizzando la funzione matrix.setPolyToPoly per trasformare una regione selezionata (4 angoli) di una bitmap in un rettangolo e normalmente funziona in modo sorprendente. Ma nel prossimo esempio:

La funzione polyToPoly fallisce la prospettiva trasformano:

ho disegnato due linee per i test, le linee di Mark dove voglio i quattro punti selezionati .

Cosa sto facendo male? Grazie!

EDIT: Ho risolto il problema utilizzando canvas.drawBitmapMesh, grazie pskink per il vostro consiglio !!

Questo è il codice finale

private float[] generateVertices(int widthBitmap, int heightBitmap) { 
    float[] vertices=new float[(WIDTH_BLOCK+1)*(HEIGHT_BLOCK+1)*2]; 

    float widthBlock = (float)widthBitmap/WIDTH_BLOCK; 
    float heightBlock = (float)heightBitmap/HEIGHT_BLOCK; 

    for(int i=0;i<=HEIGHT_BLOCK;i++) 
     for(int j=0;j<=WIDTH_BLOCK;j++) { 
      vertices[i * ((HEIGHT_BLOCK+1)*2) + (j*2)] = j * widthBlock; 
      vertices[i * ((HEIGHT_BLOCK+1)*2) + (j*2)+1] = i * heightBlock; 
     } 
    return vertices; 
} 

private Bitmap perspectiveTransformation(Bitmap bitmap, ArrayList<Point> bitmapPoints) { 

    Bitmap correctedBitmap; 
    int maxX = (int) Math.max(Math.abs(bitmapPoints.get(0).x - bitmapPoints.get(1).x), Math.abs(bitmapPoints.get(2).x - bitmapPoints.get(3).x)); 
    int maxY = (int) Math.max(Math.abs(bitmapPoints.get(0).y - bitmapPoints.get(3).y), Math.abs(bitmapPoints.get(1).y - bitmapPoints.get(2).y)); 
    Log.d("max", "x=" + maxX + " y=" + maxY); //This is the desired final size 

    Bitmap.Config conf = Bitmap.Config.ARGB_8888; 
    correctedBitmap = Bitmap.createBitmap(maxX,maxY,conf); //the final bitmap 
    float mVertices[] =generateVertices(bitmap.getWidth(),bitmap.getHeight()); 

    Point mLeftTop = bitmapPoints.get(0); 
    Point mRightTop = bitmapPoints.get(1); 
    Point mLeftBot = bitmapPoints.get(3); 
    Point mRightBot = bitmapPoints.get(2); //the points on the image where the user has clicked 

    Canvas canvas = new Canvas(correctedBitmap); 

    Matrix matrix = new Matrix(); 
    matrix.setPolyToPoly(
      new float[]{mLeftTop.x, mLeftTop.y, 
        mRightTop.x, mRightTop.y, 
        mRightBot.x, mRightBot.y, 
        mLeftBot.x, mLeftBot.y //the user's points 
      }, 
      0, 
      new float[]{0, 0, 
        maxX - 1, 0, 
        maxX - 1, maxY - 1, 
        0, maxY - 1    //where I want the user points in the corrected image 
      } 
      , 0, 4); 

    canvas.concat(matrix); 

    Paint paint = new Paint(); 
    paint.setAntiAlias(true);  //testing parameters 
    paint.setFilterBitmap(true); //testing parameters 

    paint.setColor(Color.BLUE); 
    paint.setStyle(Paint.Style.STROKE); 

    canvas.drawBitmapMesh(bitmap, WIDTH_BLOCK , HEIGHT_BLOCK, mVertices,0,null,0, paint); //draw the original bitmap into the corrected bitmap with PolyToPoly transformation matrix 

    canvas.drawLine(mLeftTop.x, mLeftTop.y, mRightBot.x, mRightBot.y, paint); //draw two lines for testing the transformation matrix 
    canvas.drawLine(mLeftBot.x, mLeftBot.y, mRightTop.x, mRightTop.y, paint); 

    //bitmap.recycle(); //just testing 

    return correctedBitmap; 
} 

Answer 1

private float[] generateVertices(int widthBitmap, int heightBitmap) { 
    float[] vertices=new float[(WIDTH_BLOCK+1)*(HEIGHT_BLOCK+1)*2]; 

    float widthBlock = (float)widthBitmap/WIDTH_BLOCK; 
    float heightBlock = (float)heightBitmap/HEIGHT_BLOCK; 

    for(int i=0;i<=HEIGHT_BLOCK;i++) 
     for(int j=0;j<=WIDTH_BLOCK;j++) { 
      vertices[i * ((HEIGHT_BLOCK+1)*2) + (j*2)] = j * widthBlock; 
      vertices[i * ((HEIGHT_BLOCK+1)*2) + (j*2)+1] = i * heightBlock; 
     } 
    return vertices; 
} 

private Bitmap perspectiveTransformation(Bitmap bitmap, ArrayList<Point> bitmapPoints) { 

    Bitmap correctedBitmap; 
    int maxX = (int) Math.max(Math.abs(bitmapPoints.get(0).x - bitmapPoints.get(1).x), Math.abs(bitmapPoints.get(2).x - bitmapPoints.get(3).x)); 
    int maxY = (int) Math.max(Math.abs(bitmapPoints.get(0).y - bitmapPoints.get(3).y), Math.abs(bitmapPoints.get(1).y - bitmapPoints.get(2).y)); 
    Log.d("max", "x=" + maxX + " y=" + maxY); //This is the desired final size 

    Bitmap.Config conf = Bitmap.Config.ARGB_8888; 
    correctedBitmap = Bitmap.createBitmap(maxX,maxY,conf); //the final bitmap 
    float mVertices[] =generateVertices(bitmap.getWidth(),bitmap.getHeight()); 

    Point mLeftTop = bitmapPoints.get(0); 
    Point mRightTop = bitmapPoints.get(1); 
    Point mLeftBot = bitmapPoints.get(3); 
    Point mRightBot = bitmapPoints.get(2); //the points on the image where the user has clicked 

    Canvas canvas = new Canvas(correctedBitmap); 

    Matrix matrix = new Matrix(); 
    matrix.setPolyToPoly(
      new float[]{mLeftTop.x, mLeftTop.y, 
        mRightTop.x, mRightTop.y, 
        mRightBot.x, mRightBot.y, 
        mLeftBot.x, mLeftBot.y //the user's points 
      }, 
      0, 
      new float[]{0, 0, 
        maxX - 1, 0, 
        maxX - 1, maxY - 1, 
        0, maxY - 1    //where I want the user points in the corrected image 
      } 
      , 0, 4); 

    canvas.concat(matrix); 

    Paint paint = new Paint(); 
    paint.setAntiAlias(true);  //testing parameters 
    paint.setFilterBitmap(true); //testing parameters 

    paint.setColor(Color.BLUE); 
    paint.setStyle(Paint.Style.STROKE); 

    canvas.drawBitmapMesh(bitmap, WIDTH_BLOCK , HEIGHT_BLOCK, mVertices,0,null,0, paint); //draw the original bitmap into the corrected bitmap with PolyToPoly transformation matrix 

    canvas.drawLine(mLeftTop.x, mLeftTop.y, mRightBot.x, mRightBot.y, paint); //draw two lines for testing the transformation matrix 
    canvas.drawLine(mLeftBot.x, mLeftBot.y, mRightTop.x, mRightTop.y, paint); 

    //bitmap.recycle(); //just testing 

    return correctedBitmap; 
}