CODEWITHSUNDEEP
androidmatrixbitmaprotation
Nick
Nick

Reputation: 6940

Generating rotated bitmaps without resizing

I'm trying to build a ring from twenty copies of a single image, which is a 1/20th slice of the full ring. I generate bitmaps that are this original image rotated to their correct degree amounts. The original image is a 130x130 square

original slice

The code that generates the rotated slices looks like this:

Bitmap bmp = BitmapFactory.decodeResource(context.getResources(), R.drawable.battery_green);
    FileOutputStream fos;
    for(int i = 0; i < 20; i++) {
        String idName = "batt_s_"+i;
        Matrix m = new Matrix();
        m.setRotate((i * 18)-8, bmp.getWidth()/2, bmp.getHeight()/2);

        Bitmap newBmp = Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), m, true);
        try {
            fos = context.openFileOutput(idName+"_"+color+".png", Context.MODE_WORLD_READABLE);
            newBmp.compress(CompressFormat.PNG, 100, fos);
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        m.reset();
        BattConfigureSmall.saveInitPref(context, true);
    }

The ImageViews that these generated bitmaps are eventually being slotted into all have scaleType="center" in their XML. However, the generated output looks like this:

enter image description here

Not exactly a perfect ring. The slices themselves, if rotated correctly, do make a perfect ring, because in API level 11 and up I'm using the android:rotate XML attribute on these ImageViews, but I need to support API levels 7-10 as well, so can anybody give me some advice? Thank you.

Upvotes: 3

Views: 885

Answers (1)

kabuko
kabuko

Reputation: 36302

Don't use the matrix with createBitmap for this scenario, it'll do some odd things with image sizing, I think. Instead, create a new Bitmap and Canvas then draw to it with the matrix:

Bitmap bmp = BitmapFactory.decodeResource(context.getResources(), R.drawable.battery_green);
FileOutputStream fos;
Paint paint = new Paint();
paint.setAntiAlias(true);
Matrix m = new Matrix();

for(int i = 0; i < 20; i++) {
    String idName = "batt_s_"+i;
    m.setRotate((i * 18)-8, bmp.getWidth()/2, bmp.getHeight()/2);

    Bitmap newBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(newBmp);
    canvas.drawBitmap(bmp, m, paint);

    try {
        fos = context.openFileOutput(idName+"_"+color+".png", Context.MODE_WORLD_READABLE);
        newBmp.compress(CompressFormat.PNG, 100, fos);
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    m.reset();
    BattConfigureSmall.saveInitPref(context, true);
}

Upvotes: 1

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