前言

　　Bitmap開發涉及到方方面面，比如裁剪圖片，壓縮圖片，映象圖片，旋轉圖片等等，是必需掌握Android開發技巧，Android開發提供了2個類來實現這些需求，Bitmap類與BitmapFactory類。此部落格會持續更新各種實際需求。

將Res點陣圖資源轉成Bitmap

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);

將Drawable向量圖資源轉成Bitmap

    public static Bitmap getBitmapFromDrawable(Context context, @DrawableRes int
 
 drawableId) {
        Drawable drawable = ContextCompat.getDrawable(context, drawableId);
        if (drawable instanceof BitmapDrawable) {
            return ((BitmapDrawable) drawable).getBitmap();
        } else if (drawable instanceof VectorDrawable || drawable instanceof VectorDrawableCompat) {
            Bitmap 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;
        } 
 
else {
            throw new IllegalArgumentException("unsupported drawable type");
        }
    }

映象垂直翻轉

        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
        Matrix matrix = new Matrix();
        matrix.postScale(1, -1);   //映象垂直翻轉
        Bitmap changBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);

映象水平翻轉

        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
        Matrix matrix = new Matrix();
        matrix.postScale(-1, 1);   //映象水平翻轉
        Bitmap changBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
        mBinding.weatherIcon.setImageBitmap(changBitmap);

旋轉圖片

        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
        Matrix matrix = new Matrix();
        matrix.postRotate(-90);  //旋轉-90度
        Bitmap changBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
        mBinding.weatherIcon.setImageBitmap(changBitmap);

End