Question

I’ve the following code for implementing zoom image in Android:

public class MyActivity extends Activity{
Matrix matrix = new Matrix();
    Matrix savedMatrix = new Matrix();
    float scaleWidth, scaleHeight,screenWidth,screenHeight;
    ImageView imageView;
@Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Display display = ((WindowManager) getApplicationContext()
                .getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
        screenWidth=display.getWidth();
        screenHeight=display.getHeight();
        imageView = (ImageView) findViewById(R.id.imageview);
        imageView.setScaleType(ScaleType.MATRIX);
        Bitmap cur_bm = BitmapFactory.decodeResource(getResources(),
                R.drawable.myimage);
        float imageWidth = (float) cur_bm.getWidth();
        float imageHeight = (float) cur_bm.getHeight();
        float newHeight = screenHeight;
        float newWidth = screenWidth;
        scaleWidth = screenWidth / imageWidth;
        scaleHeight = newHeight / imageHeight;
        imageView.setImageBitmap(cur_bm);
        SetImageMatrix();
    }

    void SetImageMatrix() {
        Matrix mtrx = new Matrix();
        scaleWidth+=0.6;
        scaleHeight+=0.6;
        mtrx.postScale(scaleWidth, scaleHeight,screenWidth/2, screenHeight/2);
        imageView.setImageMatrix(mtrx);
        imageView.invalidate();
    }
}

If I comment the line imageView.setScaleType(ScaleType.MATRIX); and comment out the function SetImageMatrix(), then the image appears as follows in the emulator:

But if I uncomment the line imageView.setScaleType(ScaleType.MATRIX); and keep the function commented, then the image appears as follows in the emulator:

Just setting the scaleType to MATRIX causes the image to scale down. Could someone please tell why this happens and how to overcome this issue?

Answer 1

Finally, I found the answer to this on one of the posts’…

Matrix m = imageView.getImageMatrix();

//Get the image's rect
RectF drawableRect = new RectF(0, 0, DrawView.imageWidth.floatValue(),
        DrawView.imageHeight.floatValue());
//Get the image view's rect
RectF viewRect = new RectF(0, 0, imageView.getWidth(),
        imageView.getHeight());
//draw the image in the view
m.setRectToRect(drawableRect, viewRect, Matrix.ScaleToFit.CENTER);
//set scale
m.postScale(scaleWidth.floatValue(), scaleHeight.floatValue(), x, y);
imageView.setImageMatrix(m);
imageView.invalidate();