Load large picture from file and add watermark

Question

I am trying to find an efficient way to load a Bitmap from a file containing an arbitrarily large image, place a watermark (a logo) over it, and save it back to fil

Answer 1

Using BitmapFactory.decodeFile(File) leads to OutOfMemory issues when decoding large pictures

OutOfMemoryError occurs because there is no single block of heap space big enough for your request. The Dalvik garbage collector is a non-compacting collector, and so the heap will get fragmented into lots of smaller blocks of memory.

If all of the pictures will be the same resolution, and your minSdkVersion is 11 or higher, then allocate the Bitmap for it when your process starts up (e.g., in onCreate() of a custom Application class), and use that with inBitmap on your BitmapFactory.Options. Your attempt to allocate the Bitmap should succeed early on, before your heap gets fragmented, if the image can fit in the heap in the first place.

If they will not all be the same resolution, but you know the maximum resolution, and your minSdkVersion is 19 or higher, then do the same thing as I describe above. Android 4.4 extended inBitmap to support a Bitmap that is the same size or bigger than the image you are loading, whereas before it had to match the size exactly.

If none of that is possible:

• Use android:largeHeap="true" to get a larger heap on API Level 11+ devices, or

• Move your image-processing logic to the NDK, as native memory allocations do not count against the Dalvik heap limit, or

• Move your image-processing logic to a dedicated short-lived process, so you get a clean separate heap at the point in time when you need to process a particular image

Those latter three options have costs to the user in terms of the system RAM consumption of your app and other effects.