读取sd卡下图片，由图片路径转换为bitmap

public Bitmap convertToBitmap(String path, int w, int h) {

BitmapFactory.Options pts = new BitmapFactory.Options();

// 设置为ture只获取图片大小

opts.inJustDecodeBounds = true;

opts.inPreferredConfig = Bitmap.Config.ARGB_8888;

// 返回为空

BitmapFactory.decodeFile(path, opts);

int width = opts.outWidth;

int height = opts.outHeight;

float scaleWidth = 0.f, scaleHeight = 0.f;

if (width > w || height > h) {

// 缩放

scaleWidth = ((float) width) / w;

scaleHeight = ((float) height) / h;

}

opts.inJustDecodeBounds = false;

float scale = Math.max(scaleWidth, scaleHeight);

opts.inSampleSize = (int)scale;

WeakReference weak = new WeakReference(BitmapFactory.decodeFile(path, opts));

return Bitmap.createScaledBitmap(weak.get(), w, h, true);

}

其中w和h你需要转换的大小

path转换为bitmap:上面方法即可；

imageview获取drawable并转换为 bitmap ：Bitmap bt= ((BitmapDrawable) mImageview.getDrawable()).getBitmap();

resourceid转换为bitmap：Bitmap bt = BitmapFactory.decodeResource(getResources(), R.drawable.resourceid);

Drawable转换为bitmap：Bitmap bt= ((BitmapDrawable) Drawable).getBitmap();

因为BitmapDrawable是继承Drawable，所以可以灵活的转换