openmv/src/omv/imlib/integral.c
2021-02-14 16:47:45 +02:00

119 lines
3.2 KiB
C

/*
* This file is part of the OpenMV project.
*
* Copyright (c) 2013-2021 Ibrahim Abdelkader <iabdalkader@openmv.io>
* Copyright (c) 2013-2021 Kwabena W. Agyeman <kwagyeman@openmv.io>
*
* This work is licensed under the MIT license, see the file LICENSE for details.
*
* Integral image.
*/
#include <stdlib.h>
#include <string.h>
#include <arm_math.h>
#include "imlib.h"
#include "fb_alloc.h"
void imlib_integral_image_alloc(i_image_t *sum, int w, int h)
{
sum->w = w;
sum->h = h;
sum->data = fb_alloc(w * h * sizeof(*sum->data), FB_ALLOC_NO_HINT);
}
void imlib_integral_image_free(i_image_t *sum)
{
// 1 allocation
fb_free();
}
void imlib_integral_image(image_t *src, i_image_t *sum)
{
typeof(*src->data) *img_data = src->data;
typeof(*sum->data) *sum_data = sum->data;
// Compute first column to avoid branching
for (int s=0, x=0; x<src->w; x++) {
/* sum of the current row (integer) */
s += img_data[x];
sum_data[x] = s;
}
for (int y=1; y<src->h; y++) {
/* loop over the number of columns */
for (int s=0, x=0; x<src->w; x++) {
/* sum of the current row (integer) */
s += img_data[y*src->w+x];
sum_data[y*src->w+x] = s+sum_data[(y-1)*src->w+x];
}
}
}
void imlib_integral_image_scaled(image_t *src, i_image_t *sum)
{
typeof(*src->data) *img_data = src->data;
typeof(*sum->data) *sum_data = sum->data;
int x_ratio = (int)((src->w<<16)/sum->w) +1;
int y_ratio = (int)((src->h<<16)/sum->h) +1;
// Compute first column to avoid branching
for (int s=0, x=0; x<sum->w; x++) {
int sx = (x*x_ratio)>>16;
/* sum of the current row (integer) */
s += img_data[sx];
sum_data[x] = s;
}
for (int y=1; y<sum->h; y++) {
int sy = (y*y_ratio)>>16;
/* loop over the number of columns */
for (int s=0, x=0; x<sum->w; x++) {
int sx = (x*x_ratio)>>16;
/* sum of the current row (integer) */
s += img_data[sy*src->w+sx];
sum_data[y*sum->w+x] = s+sum_data[(y-1)*sum->w+x];
}
}
}
void imlib_integral_image_sq(image_t *src, i_image_t *sum)
{
typeof(*src->data) *img_data = src->data;
typeof(*sum->data) *sum_data = sum->data;
// Compute first column to avoid branching
for (uint32_t s=0, x=0; x<src->w; x++) {
/* sum of the current row (integer) */
s += img_data[x] * img_data[x];
sum_data[x] = s;
}
for (uint32_t y=1; y<src->h; y++) {
/* loop over the number of columns */
for (uint32_t s=0, x=0; x<src->w; x++) {
/* sum of the current row (integer) */
s += img_data[y*src->w+x] * img_data[y*src->w+x];
sum_data[y*src->w+x] = s+sum_data[(y-1)*src->w+x];
}
}
}
uint32_t imlib_integral_lookup(i_image_t *sum, int x, int y, int w, int h)
{
#define PIXEL_AT(x,y)\
(sum->data[((y)-1)*sum->w+((x)-1)])
if (x==0 && y==0) {
return PIXEL_AT(w,h);
} else if (y==0) {
return PIXEL_AT(w+x, h) - PIXEL_AT(x, h);
} else if (x==0) {
return PIXEL_AT(w, h+y) - PIXEL_AT(w, y);
} else {
return PIXEL_AT(w+x, h+y) + PIXEL_AT(x, y) - PIXEL_AT(w+x, y) - PIXEL_AT(x, h+y);
}
#undef PIXEL_AT
}