Decode byte array to bitmap that has been compressed in Java

Question

I am compressing a bitmap in the following way

Bitmap bmpSig = getMyBitMap();
int size = bmpSig.getWidth() * bmpSig.getHeight();
ByteArrayOutputStream out = new ByteArrayOutputStream(size);
bmpSig.compress(Bitmap.CompressFormat.JPEG, 100, out);   
byte[] bytSig = out.toByteArray();

I am then trying to display the image in an Android ImageView from the byte array. When I do this I get an image that is completely black image.

ImageView myImg = (ImageView) findViewById(R.id.img_view);
myImg.setImageBitmap(BitmapFactory.decodeByteArray(bytSig, 0, bytSig.length));

I'm assuming it's because I am missing a step before BitmapFactory.decodeByteArray() to reverse the jpeg compression. Or have I misunderstood how the compression works?

cutts · Accepted Answer · 2011-03-09 09:38:42Z

6

I didn't realise that the background of my bitmap (from a Canvas object) was transparent. Since this bitmap is just black lines on a white background the black image is due to compressing to JPEG giving the image a black background.

I have changed

bmpSig.compress(Bitmap.CompressFormat.JPEG, 100, out);

to

bmpSig.compress(Bitmap.CompressFormat.PNG, 100, out);

And it is working as expected.

answered Mar 9, 2011 at 9:38

cutts

5831 gold badge5 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Stephen C Over a year ago

Nah ... you just needed to use a darker shade of black.

Collectives™ on Stack Overflow

Decode byte array to bitmap that has been compressed in Java

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related