CODEWITHSUNDEEP
android
Martin
Martin

Reputation: 4836

rotate bitmap and maintain size

I am creating a tile board game. I want to rotate a bitmap tile piece by a few pre-determined degrees.
When I rotate my bitmap, the size changes.
For example, if I want a 75x75 triangle tile piece, on rotation I get a 68x68 back from this code. How can I keep things the same size so everything remains the size for the board?

Here's what I'm using to rotate:

public class RotatebitmapActivity extends Activity {
@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    LinearLayout linLayout = new LinearLayout(this);

    // load the origial BitMap (500 x 500 px)
    Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(), 
           R.drawable.t123);

    int width = bitmapOrg.getWidth();
    int height = bitmapOrg.getHeight();
    int newWidth = 75;
    int newHeight = 75;

    // calculate the scale - in this case = 0.4f
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;

    // createa matrix for the manipulation
    Matrix matrix = new Matrix();
    // resize the bit map
    matrix.postScale(scaleWidth, scaleHeight);
    // rotate the Bitmap
    matrix.postRotate(120);

    // recreate the new Bitmap
    Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, 
                      width, height, matrix, true); 


    // make a Drawable from Bitmap to allow to set the BitMap 
    // to the ImageView, ImageButton or what ever
    BitmapDrawable bmd = new BitmapDrawable(resizedBitmap);

    ImageView imageView = new ImageView(this);

    // set the Drawable on the ImageView
    imageView.setImageDrawable(bmd);

    // center the Image
    imageView.setScaleType(ScaleType.CENTER);

    // add ImageView to the Layout
    linLayout.addView(imageView, 
        new LinearLayout.LayoutParams(
                  LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT
            )
    );

    // set LinearLayout as ContentView
    setContentView(linLayout);
}

Upvotes: 1

Views: 2933

Answers (1)

DavidDraughn
DavidDraughn

Reputation: 1131

What is happening in your code, is that the bitmap that is created is the correct size. However, all Bitmaps are automatically scaled to fit the density of the screen that is currently in use.

There are two ways (that I know of) to get the result you desire.

  1. You can set the density of a bitmap after creating it and before wrapping it in a drawable. To do this, add code similar to:

    resizedBitmap.setDensity(DisplayMetric.DENSITY_HIGH);

    This code sets the density that the bitmap is designed for, and can prevent Android from auto-scaling the image.

  2. The second solution is more of a methodology than a specific solution to this particular problem. I won't go into detail, for that see Supporting Multiple Screens | Android Developers

Hopefully someone will happen along that can answer your question better than I can.

Upvotes: 1

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