convert 24bit RGB to ARGB16

Question

I have to read a 24bpp Bitmap and convert each pixel from RGB24 to ARGB16.

I used the following code,

#define ARGB16(a, r, g, b) ( ((a) << 15) | (r)|((g)<<5)|((b)<<10))

But I am not getting the required Output.

Any help would be highly appreciated.

Answer 1

Break it up. Let's continue to use macros:

#define TRUNCATE(x)  ((x) >> 3)

#define ARGB16(a,r,g,b) ((a << 15) | (TRUNCATE(r) << 10) | (TRUNCATE(g) << 5) | TRUNCATE(b)))

This assumes the alpha is just a single bit.