How to get the size (Kb or Mb ) of Bitmap in android java

Question

I have a Bitmap and I want to get the size of the bitmap in KB, MB or etc

TRID NUMBER 1 - so I tried this but it is returning the wrong output because I have an image whose size is 42.57 KB but in the result, it is returning 128 B

    // originalBitmap is global var

    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    originalBitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
    byte[] imageInByte = stream.toByteArray();
    long bitmap_size = imageInByte.length / 1024;
    Log.d(TAG, "size of bitmap - "+Formatter.formatShortFileSize(this,bitmap_size));

TRID NUMBER 2 - so In this tried is simply done this thing but it is also showing wrong output it showing 1.2 MB of that same image whose size is 42.57 KB

Log.d(TAG, "Image size : "+Formatter.formatShortFileSize(this, originalBitmap.getByteCount()));

NOTE: I have no real device so tested this in the emulator. may this cause or what do you think

any help will be appreciated. thank you.

Answer 1

Don't divide by 1024

long bitmap_size = imageInByte.length / 1024;

If you are using Formatter.formatShortFileSize then just use the original length of the byte array.

This code is compressing the image with this:

originalBitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);

How do you know the size of the image after this compression? You might write the compressed image out to a file, however the imageInByte.length has to be the number of bytes in the byte array. Are you sure it is NOT this size?

Answer 2

You said " I have an image whose size is 42.57 KB " and I suppose it isn't a real Bitmap but some JPEG, PNG, WEBP or other image format. If you import this image in Java using BitmapFactory the decoder "expands" compressed image bytes in a real Bitmap made by Width x Height x 3 (or "4" if apha is supported from original image format). So a simple 1Kb image of 100x100 PNG file could became 100x100*3 = 30000 = 30Kb in Java when " Bitmap.getByteCount() " is executed. Compressing (again) this 30Kb Bitmap in a different or similar format could generate a different output so a different final length.

Maybe you need some explanation:

1. a Bitmap, in Java, is just an array of bytes. A Bitmap, as a file, is made by an Header and same array of bytes.
2. if you Compress a Java Bitmap into a JPEG Stream you will get the final JPEG with exactly same content you need to write in a file (aka: this output could not be directly displayed in Java)

So you're Compressing a Bitmap to get a compressed JPEG and then you're getting JPEG length (header included). Obliviously a compressed file is normally smaller than original one.

• If you don't want JPEG length but Bitmap length you were near right by doing "Formatter.formatShortFileSize(this, BITMAP .getByteCount())".
• If you want JPEG length (the one after Compression) then don't divide by 1024 because Formatter needs Bytes and not Kilobytes.

Comparing a Compressed or not-Compressed Java output with original Image File is 99% of times "wrong" because re-compressing a decompressed image file usually results in a different result.