Android. Obtaining image size from it's resource id

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Solution 1

Use BitmapFactory.decodeResource to obtain a Bitmap object of the resource, and then from the bitmap you can easily retrieve the image width/height with getHeight and getWidth

Also do not forget to recycle your bitmap

EDIT:

This way you will get a null bitmap as output, but the BitmapFactory.Options will be set with the with and height for the bitmap. So, in this case,, you do not need to recycle the bitmap

BitmapFactory.Options dimensions = new BitmapFactory.Options(); 
dimensions.inJustDecodeBounds = true;
Bitmap mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.bitmap, dimensions);
int height = dimensions.outHeight;
int width =  dimensions.outWidth;

Solution 2

For anyone that didn't read dmon's comment. The code to do this looks like this:

final Options opt = new BitmapFactory.Options();
opt.inJustDecodeBounds = true;
BitmapFactory.decodeResource(getResources(), R.drawable.your_photo, opt);

opt.outHeight; // height of resource
opt.outWidth; // width of resource
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alex
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alex

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Updated on June 04, 2022

Comments

  • alex
    alex over 1 year

    This is a part of my Activity:

    private ImageView mImageView;
    private int resource;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      resource = getIntent().getIntExtra("res", -1);
    
      Matrix initMatrix = new Matrix();
    
      mImageView = new ImageView(getApplicationContext());
      mImageView.setScaleType( ImageView.ScaleType.MATRIX );
      mImageView.setImageMatrix( initMatrix );
      mImageView.setBackgroundColor(0);
      mImageView.setImageResource(resource);
    }
    

    I try to display an image within an ImageView using a matrix as scale type (I want to add multitouch later). But before user starts interaction i want the image to be centered and fit inside the ImageView. I already found answers concerning how to solve it but there is one problem for me: to make image centered using matrix I need to know its width and height. Is there any way of getting image size when all you have is int resource ?

  • dmon
    dmon over 11 years
    You should also use BitmapFactory.Options dimensions = new BitmapFactory.Options(); dimensions.inJustDecodeBounds = true; to just decode the image dimensions without actually loading the bitmap into memory.
  • Warpspace
    Warpspace almost 11 years
    Do you mean BitmapFactory.decodeResource(getResources(), R.drawable.your_photo, opt);?
  • Ankit
    Ankit over 10 years
    For me why mBitmap is coming as null if I set inJustDecodeBounds = true? If I set it to false it is returning me a bitmap.
  • Blackbelt
    Blackbelt over 10 years
    @Ankit it is the normali behaviour and it is described in the documentation
  • Ankit
    Ankit over 10 years
    @blackbelt I just want to know the dimensions of image I don't want to load it in memory but with above code I am getting nullPointerException when calling getHeight() and getWidth().
  • Blackbelt
    Blackbelt over 10 years
    @Ankit thanks to point out, it was a mistake. I have update my answer
  • Raanan
    Raanan about 10 years
    @blackbelt, great answer, should mention that after your EDIT you don't need to recycle the bitmap either (since you don't get one).
  • Blackbelt
    Blackbelt about 10 years
    @Raanan I am going to put it right now. Thanks for pointing it out
  • SBotirov
    SBotirov over 8 years
    Thanks @xbakesx best solution!
  • user1122069
    user1122069 over 7 years
    @Blackbelt As far as I can tell, there is no need to recycle the bitmap. Maybe something has changed, but the docs state "This is an advanced call, and normally need not be called, since the normal GC process will free up this memory when there are no more references to this bitmap." and "This will not free the pixel data synchronously; it simply allows it to be garbage collected" --- No memory is freed by calling recycle until the next GC process, at which point the Bitmap is long out of scope.
  • Blackbelt
    Blackbelt over 7 years
    @user1122069, there is no need anymore you are right. The real need was for really old platforms, up to gingerbread