Split the Image in Pieces

app/src/main/java/dragosholban/com/androidpuzzlegame/MainActivity.java

@@ -1,13 +1,124 @@
package dragosholban.com.androidpuzzlegame;

import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.constraint.ConstraintLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

import java.util.ArrayList;

import static java.lang.Math.abs;

public class MainActivity extends AppCompatActivity {
    ArrayList<Bitmap> pieces;

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

        final ConstraintLayout layout = findViewById(R.id.layout);
        ImageView imageView = findViewById(R.id.imageView);

        // run image related code after the view was laid out
        // to have all dimensions calculated
        imageView.post(new Runnable() {
            @Override
            public void run() {
                pieces = splitImage();
                for(Bitmap piece : pieces) {
                    ImageView iv = new ImageView(getApplicationContext());
                    iv.setImageBitmap(piece);
                    layout.addView(iv);
                }
            }
        });
    }

    private ArrayList<Bitmap> splitImage() {
        int piecesNumber = 12;
        int rows = 4;
        int cols = 3;

        ImageView imageView = findViewById(R.id.imageView);
        ArrayList<Bitmap> pieces = new ArrayList<>(piecesNumber);

        // Get the scaled bitmap of the source image
        BitmapDrawable drawable = (BitmapDrawable) imageView.getDrawable();
        Bitmap bitmap = drawable.getBitmap();

        int[] dimensions = getBitmapPositionInsideImageView(imageView);
        int scaledBitmapLeft = dimensions[0];
        int scaledBitmapTop = dimensions[1];
        int scaledBitmapWidth = dimensions[2];
        int scaledBitmapHeight = dimensions[3];

        int croppedImageWidth = scaledBitmapWidth - 2 * abs(scaledBitmapLeft);
        int croppedImageHeight = scaledBitmapHeight - 2 * abs(scaledBitmapTop);

        Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, scaledBitmapWidth, scaledBitmapHeight, true);
        Bitmap croppedBitmap = Bitmap.createBitmap(scaledBitmap, abs(scaledBitmapLeft), abs(scaledBitmapTop), croppedImageWidth, croppedImageHeight);

        // Calculate the with and height of the pieces
        int pieceWidth = croppedImageWidth/cols;
        int pieceHeight = croppedImageHeight/rows;

        // Create each bitmap piece and add it to the resulting array
        int yCoord = 0;
        for (int row = 0; row < rows; row++) {
            int xCoord = 0;
            for (int col = 0; col < cols; col++) {
                pieces.add(Bitmap.createBitmap(croppedBitmap, xCoord, yCoord, pieceWidth, pieceHeight));
                xCoord += pieceWidth;
            }
            yCoord += pieceHeight;
        }

        return pieces;
    }

    private int[] getBitmapPositionInsideImageView(ImageView imageView) {
        int[] ret = new int[4];

        if (imageView == null || imageView.getDrawable() == null)
            return ret;

        // Get image dimensions
        // Get image matrix values and place them in an array
        float[] f = new float[9];
        imageView.getImageMatrix().getValues(f);

        // Extract the scale values using the constants (if aspect ratio maintained, scaleX == scaleY)
        final float scaleX = f[Matrix.MSCALE_X];
        final float scaleY = f[Matrix.MSCALE_Y];

        // Get the drawable (could also get the bitmap behind the drawable and getWidth/getHeight)
        final Drawable d = imageView.getDrawable();
        final int origW = d.getIntrinsicWidth();
        final int origH = d.getIntrinsicHeight();

        // Calculate the actual dimensions
        final int actW = Math.round(origW * scaleX);
        final int actH = Math.round(origH * scaleY);

        ret[2] = actW;
        ret[3] = actH;

        // Get image position
        // We assume that the image is centered into ImageView
        int imgViewW = imageView.getWidth();
        int imgViewH = imageView.getHeight();

        int top = (int) (imgViewH - actH)/2;
        int left = (int) (imgViewW - actW)/2;

        ret[0] = left;
        ret[1] = top;

        return ret;
    }
}

app/src/main/res/layout/activity_main.xml

@@ -4,15 +4,23 @@
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="dragosholban.com.androidpuzzlegame.MainActivity">
    tools:context="dragosholban.com.androidpuzzlegame.MainActivity"
    android:id="@+id/layout">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:scaleType="centerCrop"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/photo" />
</android.support.constraint.ConstraintLayout>