Android-Bitmap 圖片編輯

Resources 轉 Drawable

Drawable d = getResources().getDrawable(R.drawable.icon);

Resources 轉 Bitmap

Bitmap mBitmap = BitmapFactory.decodeResource(this.getResources(), 
                R.drawable.test_image);

Drawable 轉 Bitmap

public static Bitmap drawableToBitmap (Drawable drawable) {
    Bitmap bitmap = null;

    if (drawable instanceof BitmapDrawable) {
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
        if(bitmapDrawable.getBitmap() != null) {
            return bitmapDrawable.getBitmap();
        }
    }

    if(drawable.getIntrinsicWidth() <= 0 || drawable.getIntrinsicHeight() <= 0) {
        bitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888); 
    } else {
        bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), 
            drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
    }

    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
    drawable.draw(canvas);
    return bitmap;
}

Bitmap 轉 Drawable

Drawable d = new BitmapDrawable(getResources(), bitmap);

使用 Bitmap 更改長寬

public Bitmap getResizedBitmap(Bitmap bm, int newHeight, int newWidth) {
    int width = bm.getWidth();
    int height = bm.getHeight();
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;
    Matrix matrix = new Matrix();
    matrix.postScale(scaleWidth, scaleHeight);
    Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, false);
    return resizedBitmap;
}

使用 Bitmap 使兩張圖片置中

private Bitmap mergeBitmap(Bitmap firstBitmap, Bitmap secondBitmap) {
    Bitmap bitmap = Bitmap.createBitmap(firstBitmap.getWidth(), firstBitmap.getHeight(),
               firstBitmap.getConfig());
    Canvas canvas = new Canvas(bitmap);
    int firstWidth = firstBitmap.getWidth();
    int firstHeight = firstBitmap.getHeight();
    int secondWidth = secondBitmap.getWidth();
    int secondHeight = secondBitmap.getHeight();
    canvas.drawBitmap(firstBitmap, new Matrix(), null);
    canvas.drawBitmap(secondBitmap, firstWidth/2-secondWidth/2, 
        firstHeight/2-secondHeight/2, null);
    return bitmap;
}

使用 Bitmap 旋轉圖片

private Bitmap rotateImage(Bitmap bitmap, float rotate){
    Matrix matrix = new Matrix();
    matrix.setRotate(rotate);
    return Bitmap.createBitmap(bitmap, 0, 0, 
        bitmap.getWidth(), bitmap.getHeight(), matrix, true);
}

參考資料 : How to convert a Drawable to a Bitmap?