34 lines
1.1 KiB
C
34 lines
1.1 KiB
C
#include <display.h>
|
|
|
|
/*
|
|
getMasks()
|
|
Computes the rectangle masks needed to affect pixels located between x1
|
|
and x2 (both included). The four masks are stored in the third argument
|
|
(seen as an array).
|
|
*/
|
|
void getMasks(int x1, int x2, uint32_t *masks)
|
|
{
|
|
// Indexes of the first and last longs that are non-blank.
|
|
int l1 = x1 >> 5;
|
|
int l2 = x2 >> 5;
|
|
int i = 0;
|
|
|
|
// Setting the base masks. Those are the final values, except for the
|
|
// longs with indexes l1 and l2, that still need to be adjusted.
|
|
while(i < l1) masks[i++] = 0x00000000;
|
|
while(i <= l2) masks[i++] = 0xffffffff;
|
|
while(i < 4) masks[i++] = 0x00000000;
|
|
|
|
// Removing the long number information in x1 and x2 (that is, the
|
|
// multiples of 32) to keep only the interesting information -- the
|
|
// number of null bits to add in l1 and l2.
|
|
x1 &= 31;
|
|
// Inverting x2 is here the same as computing 32 - x, since 32 is a
|
|
// power of 2 (positive bits at the left are removed by the mask).
|
|
x2 = ~x2 & 31;
|
|
|
|
// Setting the first and last masks.
|
|
masks[l1] &= (0xffffffff >> x1);
|
|
masks[l2] &= (0xffffffff << x2);
|
|
}
|