Generate a md5 sum from an Android Bitmap object

Question

I've spent several hours trying to figure out how to do this. I've read post after post here on stackoverflow and the documentation.

I have a android.graphics.Bitmap object and I need to get it's md5 sum. At the point that I want to verify the sum it has not been saved to the file system. I've seen several ways of doing this for java.io.File objects. I just need a function that receives a Bitmap object and returns the hex md5 sum as a String.

This might have been addressed somewhere but if it has been I have been unable to understand it or deduce how to do it from it.

The less resource heavy the method is the better it is of course.

Answer 1

Get bitmap's bytes to calculate md5.

Bitmap bm = ... // your bitmap
ByteArrayOutputStream baos = new ByteArrayOutputStream();  
bm.compress(Bitmap.CompressFormat.PNG, 100, baos); //bm is the bitmap object   
byte[] bitmapBytes = baos.toByteArray();

So you have byte array now. You can find how to get md5 hash of byte array in android here.

Answer 2

I'm not Android developer, but I see in the API reference (http://developer.android.com/reference/android/graphics/Bitmap.html) that there are methods for:

• getting size of the bitmap: getWidth, getHeight
• getting the pixels as an array of integers: getPixels

So you could just create an array of needed size, then read all the pixels, and convert the array to byte[].

Then it should be not a problem to calculate md5 sum from it.