draw circle on bitmap

问题

i've written an app that captures a picture and saves it on the sdcard. i then can load that image into an imageview to display it. i'd like to draw a circle on the bitmap before i display it. the code below displays the bitmap but no circle, any ideas why the circle is not there?

thanks.

BitmapFactory.Options bfo = new BitmapFactory.Options();
        bfo.inSampleSize = 5;
        Bitmap bm = BitmapFactory.decodeByteArray(imageArray, 0, imageArray.length, bfo);
        Log.e(TAG, bm.toString());
        //imageview.setImageBitmap(bm);


        Bitmap bmOverlay = Bitmap.createBitmap(bm.getWidth(), bm.getHeight(), bm.getConfig());
        canvas = new Canvas(bmOverlay);
        Paint paint = new Paint();
        paint.setColor(Color.RED);
        canvas.drawBitmap(bm, new Matrix(), null);
        canvas.drawCircle(750, 14, 11, paint);
        imageview.setImageBitmap(bmOverlay);

回答1:

You might check bm.getWidth. If you are using a sample size of 5 then your image will be 5 times smaller than the original, causing your circle to disappear off the right side of the image.

You could try:

paint.setStrokeWidth(10);
canvas.drawCircle(50, 50, 25);

just as a sanity check.

来源：https://stackoverflow.com/questions/5531062/draw-circle-on-bitmap