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Optimize p_box3x3_f32 function #149

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Optimize p_box3x3_f32 function #149

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b727499
Optimize p_box3x3_f32 function
Jun 16, 2015
d6caaa3
image: p_box3x3_f32: Rewitten for less verbosity
Jun 18, 2015
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62 changes: 39 additions & 23 deletions src/image/p_box3x3.c
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Original file line number Diff line number Diff line change
Expand Up @@ -21,35 +21,51 @@
void p_box3x3_f32(const float *x, float *r, int rows, int cols)
{

int ia, ja;
float E;
int i, j;
float sum;
const float *px;
float *pr;

px = x;
pr = r;
// Initialize the output pointer to the (-1, 0) coordinate
pr = r - cols + 2;

for (ia = 1; ia <= (rows - 2); ia++) {
for (ja = 1; ja <= (cols - 2); ja++) {
E = 0;
E += (*px++);
E += (*px++);
E += (*px++);
px += cols - 3;
E += (*px++);
E += (*px++);
E += (*px++);
px += cols - 3;
E += (*px++);
E += (*px++);
E += (*px++);
px += cols - 3;
*pr = E * M_DIV9;
px += 1 - 3 * cols; // advance mask matrix in one column.
for (i = 0; i < rows; i++) {
// The first sum is calculated directly.
sum = (*px) + (*(px+1)) + (*(px+2));
if (i >= 2) {
// The first two input rows do not correspond to the bottom of any
// pixel filter, so skip this logic for those rows.
*(pr-cols+2) = (*(pr-cols+2) + sum) * M_DIV9;
}
if (i != 0 && i != rows-1) {
// The first and last input rows do not correspond to the middle
// of any pixel filter, so skip this logic for those rows.
*pr += sum;
}
if (i < rows - 2) {
// The last two input rows do not correspond to the top of any
// pixel filter, so skip this logic for those rows.
*(pr+cols-2) = sum;
}
pr++;
for (j = 3; j < cols; j++) {
// All subsequent sums (in the same row) are calculated by
// removing the leftmost value, and adding the value to the
// immediate right of the currently included values.
sum += (*(px+3)) - (*px);
if (i >= 2) {
*(pr-cols+2) = (*(pr-cols+2) + sum) * M_DIV9;
}
if (i != 0 && i != rows-1) {
*pr += sum;
}
if (i < rows - 2) {
*(pr+cols-2) = sum;
}
px++;
pr++;
}
px = px + 2; // advance pointer to the beginning of next row.
px += 3; // Advance input pointer to beginning of next row.
}

return;
}