CODEWITHSUNDEEP
c++indexing
Léon Pelletier
Léon Pelletier

Reputation: 2741

Changing all number in an array to their indexed value

I'm doing image processing with filters since it's cool currently, and one quick method I use to create filters is to calculate rgb curve profiles, so that I have 3 arrays, redProfile, greenProfile, blueProfile.

I'm usually doing this when I'm applying an effect on pixels in a loop:

*dest++ = bLomoRGB[top(r)];
*dest++ = gLomoRGB[top(g)];
*dest++ = rLomoRGB[top(b)];
*dest++ = 0xff;         
x++;        
if (x > 639) { x = 0; y++; }        
continue;

So, for each color, I pick the color in the profile.

Is this possible to work with matrix, or to execute it more efficiently?

i.e. Coding something like: Array a = all my pixels Array b = my index Apply b on a

I know this is simpler than pseudo-code and doesn't even deserve to be grayed as code, but I still wonder if it is relevant to always maintain a loop to do a single thing like changing all number for their indexed value.

Upvotes: 0

Views: 105

Answers (1)

nullptr
nullptr

Reputation: 11058

I doubt that there are some magic operations that perform this for the whole matrix.

However, this can be done more efficiently if you write your data by 32-bit blocks at once:

uint32_t *dest;

*dest++ = (bLomoRGB[top(r)] & 0xff) | ((gLomoRGB[top(g)] & 0xff) << 8) | 
          ((rLomoRGB[top(b)] & 0xff) << 16) | 0xff000000;

Also, the code can be quite well parallelized. If you're looking for some standard way of parallelizing such loops, take a look at OpenMP.

Upvotes: 2

Related Questions