Question

public static int NUM_FRAMES = 8;
public static int FRAME_REPEAT_NO = 2;
int height = 24;
//bitmap.getWidth() is 168 and bitmap.getHeight() is 91

double w = bitmap.getWidth();
w = w/NUM_FRAMES;
w = w*FRAME_REPEAT_NO;
w = w*height;
w = w/bitmap.getHeight();

I do this and i get the value of w as 11.07 which is correct.

But when i do this:

double w  = FRAME_REPEAT_NO*(bitmap.getWidth()/NUM_FRAMES)*(height/bitmap.getHeight());

value of w is always 0;

Can someone explain to me why this is happening?

P.S. I’m doing it in an android app…

Answer 1

Others have already addressed your question, so I won’t repeat their answers, but one suggestion I’ll make. Consider computing your result using

w = (double)(FRAME_REPEAT_NO * bitmap.getWidth() * height) / (double)(NUM_FRAMES * bitmap.getHeight())

This allows you to live in the predictable land of integers until the very end where you do the division. So any error in the result comes from a single operation instead of aggregating multiple errors. And if for whatever reason you decided you wanted to get an integer result, you can drop the doubles and still get 11 as the answer.

Not a big deal but just thought I’d put it out there.

EDIT: I saw from your comment on another post that you actually want the 11. Good. So just drop the doubles altogether:

w = (FRAME_REPEAT_NO * bitmap.getWidth() * height) / (NUM_FRAMES * bitmap.getHeight())

Answer is exactly 11 (integer), which is different by the way than the floating point approximation of 11.0.