Skipping the bitmap pool if the image to be decoded is a GIF

[savvasdalkitsis]

Exposed a method to return the type of the image to be decoded. For now supports GIF, PNG_A, PNG, JPEG and UNKNOWN

We skip the bitmap pool if the image is a GIF because of :

https://groups.google.com/forum/#!msg/android-developers/Mp0MFVFi1Fo/e8ZQ9FGdWdEJ

[sjudd]

This looks good to me, one question: Have you tested with tiffs? I realized my original code doesn't consider them in hasAlpha. From the link you posted I'd expect them to cause the same exception.

Thanks again for submitting these, I'll merge tonight if I don't get time before then.

[savvasdalkitsis]

I am not entirely sure how to check for TIFFs in the general case to be honest. What I have done now is, instead of looking for GIFs in order to skip the pool, I skip it if the type is not JPG, PNG or PNG_A (which I changed from the previous APNG which means something else btw).

This way when new types of images are added, the pool skipping will happen automatically unless we add that type to the set of recognized types. Also, I am hoping since I haven't tested, a TIFF will not return JPG or PNG with the current code, so the skipping will happen.

Let me know if this is sufficient.

[sjudd]

LGTM.

Tiffs have a different four byte header so right now they will just be classified as unknown which is fine.