App randomly crashes when phone comes back from IDLE

Hello, My app is working fine on my phone (HTC 510 desire android 4.4.2) as long as the phone is UP, but when the phone goes to IDLE and next to ACTIVE, the app crash randomly.

The crash comes from an out of memory.

Here after the error message:

FATAL EXCEPTION: Thread-88714 Process: processing.test.sketch_171102a, PID: 24348 java.lang.OutOfMemoryError: (Heap Size=65536KB, Allocated=61546KB) at android.graphics.BitmapFactory.nativeDecodeStream(Native Method) at android.graphics.BitmapFactory.decodeStreamInternal(BitmapFactory.java:739)

Questions: 1>How can I log the amount of memory allocated? 2>What can be the problem?

Thanks in advance /Pascal