What is "Bitmap source" in createBitmap() parameters?

Question

I'm following this S.O. post about how to crop an image using a Bitmap.

As confirmed in Android documentation, there is a method createBitmap() that has the following parameters:

createBitmap(Bitmap source, int x, int y, int width, int height)

But I don't understand what this Bitmap source needs to be. I believe it must refer to the image I wish to use for my Bitmap object. The image I wish to use is stored as a drawable named rainbow, so I tried the following:

    Bitmap cropedBitmap = Bitmap.createBitmap(R.id.rainbow, 0, 0, 300, 300);

In which case Android Studio reports "Cannot resolve symbol 'rainbow'

I also tried:

      Bitmap cropedBitmap = Bitmap.createBitmap(R.drawable.rainbow, 0, 0, 300, 300);

and Android Studio reports "Cannot resolve method createBitmap(int, int, int, int, int)

I see from the documentation that the first parameter is a Bitmap. Wouldn't that be using a Bitmap to create a Bitmap? Also I don't see any constructors for the Bitmap class on its documentation page.

Any suggestions on what I'm missing or what to try next?

score 0 · Answer 1 · edited May 23 '17 at 11:52

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R.drawable.rainbow is integer value not a Bitmap as it is just a generated identifier number of your resources.

You need to use a method to make drawable resource id into Bitmap object as this post did.

Edit: add options and drawable call method

BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 4;
Drawable drawable = getResources().getDrawable(R.drawable.rainbow);
Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
Bitmap cropedBitmap = Bitmap.createBitmap(bitmap, options), 0, 0, 300, 300);

edited May 23 '17 at 11:52

Community

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answered May 31 '15 at 07:14

Youngjae

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Please don't do this. This creates two bitmaps (one while decoding and then the scaled version), with the former up for garbage collection immediately. Given scarcity of bitmap memory, not creating the temporary bitmap is quite important, however. – dhke May 31 '15 at 07:20
@dhke // hi. thanks for pointint out. then how about `((BitmapDrawable)drawable).getBitmap();`? will it be same? – Youngjae May 31 '15 at 07:22
@dhke Is there a good alternative? If so would like to post an answer? – Timothy Steele May 31 '15 at 07:23
Right too much overhead loading with options resolve such problems – Ilja KO May 31 '15 at 07:23
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@TimothySteele I'd suggest to always use an image loader library. The code to do it properly becomes rather long and messy once you start considering [`imSampleSize`](https://developer.android.com/reference/android/graphics/BitmapFactory.Options.html#inSampleSize) and the like. – dhke May 31 '15 at 07:26
@Youngjae When you've got the drawable, the bitmap is already loaded, so no (additional) memory problems from accessible the internal bitmap, no. – dhke May 31 '15 at 07:30
@dhke Would you post your comment as an answer? While you didn't actually answer my question, you answered the question I should have asked. Using an Image Loader Library was the best option to solve my problem. I used the Picasso library. – Timothy Steele Sep 03 '15 at 19:59

score 0 · Answer 2 · answered May 31 '15 at 07:22

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If you want to crop out a piece of the Bitmap you can load the piece directly from resource into ram with BitmapFactory.Options Quite common when you animate things in games and the images are out of a bigger sprite

answered May 31 '15 at 07:22

Ilja KO

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What is "Bitmap source" in createBitmap() parameters?

2 Answers2