Resize a large bitmap file to scaled output file on Android

Question

I have a large bitmap (say 3888x2592) in a file. Now, I want to resize that bitmap to 800x533 and save it to another file. I normally would scale the bitmap by calling

Answer 1

To scale the image the "correct" way, without skipping any pixels, you'd have to hook into the image decoder to perform the down-sampling row by row. Android (and the Skia library that underlies it) provides no such hooks, so you'd have to roll your own. Assuming you're talking jpeg images, your best bet would be to use libjpeg directly, in C.

Given the complexities involved, using the two-step subsample-then-rescale is probably best for image-preview type apps.