android: quality of the images resized in runtime

shinydev picture shinydev · Jan 11, 2010 · Viewed 17.5k times · Source

I want to show images using drawBitmap() method. But before I want to resize it according screen dimensions. I have a problem with quality of result image. You can see screenshots and test code below. How can I resize images in runtime with a good quality?

Thank you for solutions.

Original image: alt text http://dl.dropbox.com/u/709109/gradient.png

Result screenshot on device: alt text http://dl.dropbox.com/u/709109/device.png

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.os.Bundle;
import android.view.View;
import android.widget.LinearLayout;

import java.io.IOException;
import java.io.InputStream;

public class MyActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        LinearLayout container = (LinearLayout) findViewById(R.id.container);
        container.addView(new View(this) {
            @Override
            protected void onDraw(Canvas canvas) {
                Bitmap unscaledBitmap;
                try {
                    InputStream in = getAssets().open("images/gradient.png");
                    unscaledBitmap = BitmapFactory.decodeStream(in);
                    in.close();
                    canvas.drawBitmap(unscaledBitmap, null, new Rect(0, 0, 320, 480), null);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

Answer

Romain Guy picture Romain Guy · Jan 11, 2010

Instead of resizing at drawing time (which is going to be very costly), try to resize in an offscreen bitmap and make sure that Bitmap is 32 bits (ARGB888).