Android: BitmapFactory.decodeByteArray gives pixelated bitmap

Question

I am working on an Android app that displays photos which are downloaded from Flickr. I obtain a bitmap object from a byte array, which in turn is read from the relevant Fli

Answer 1

Write the raw bytes fetched from the URL to /sdcard/tmp.jpg, and view on your PC.

JPEG images are compressed in 8x8 (or 16x16) tiles. The 'pixelation' as you describe it is actually in these tiles, suggesting that the 'bad' image is a JPEG that is more aggressively compressed than the other.

So I'd anticipate that the actual issue is that the image being downloaded is a very low-quality version, e.g. one intended for thumbnailing/preview use-cases.

Answer 2

Some version of Android have a bug in Bitmap class and convert the Bitmap to RGB_565 upon some operations. This would manifest itself in artifacts similar to those on your picture. This would also explain the banding of the blue sky. Also, have in mind that android attempts to "optimize" image by converting them to rgb_565 upon loading and even compiling in resource files. Take a look at: http://android.nakatome.net/2010/04/bitmap-basics.html

Answer 3

Ok, so I finally get it: it appears that my mobile network does image compression to save bandwidth.

Hence a picture downloaded from my phone is of lower quality than the same picture downloaded from my computer.

That's a bummer for my app, but I don't suppose there is anything I can do about it. Sigh.

Thanks again for your input though!

Best, Michael.