How to draw and scale a bitmap on a canvas using bicubic interpolation in Android?

Question

I want to draw a bitmap on a canvas with bigger size than it is. I can use canvas.drawBitmap(bitmap, null, destRect, null); but that gives a poor quality, as the result is pixel

Answer 1

FILTER_BITMAP_FLAG doesn't work for downscaling in most of the cases.

Good downscaling algorithm (not nearest neighbor like) consists of just 2 steps (plus calculation of the exact Rect for input/output images crop):

1. downscale using BitmapFactory.Options::inSampleSize->BitmapFactory.decodeResource() as close as possible to the resolution that you need but not less than it
2. get to the exact resolution by downscaling a little bit using Canvas::drawBitmap()

Here is detailed explanation how SonyMobile resolved this task: https://web.archive.org/web/20140228024414/http://developer.sonymobile.com/2011/06/27/how-to-scale-images-for-your-android-application/

Here is the source code of SonyMobile scale utils: https://web.archive.org/web/20140227233706/http://developer.sonymobile.com/downloads/code-example-module/image-scaling-code-example-for-android/