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314 lines
9.2 KiB
C
314 lines
9.2 KiB
C
/*
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* This file is part of the OpenMV project.
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*
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* Copyright (c) 2013-2021 Ibrahim Abdelkader <iabdalkader@openmv.io>
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* Copyright (c) 2013-2021 Kwabena W. Agyeman <kwagyeman@openmv.io>
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*
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* This work is licensed under the MIT license, see the file LICENSE for details.
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*
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* An integral image using a moving window.
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*
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* The high level steps are:
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* 1) Start with an array of pointers[n] where n = feature height.
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* 2) Compute the first n lines of the integral image.
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* 3) Do some processing with the integral image.
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* 4) Call integral_mw_image_shift(n)
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*
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* This will shift the pointers by n and calculate n new lines, example:
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* Assuming feature height is 4:
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* mw_i_image[0] -> mem[0]
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* mw_i_image[1] -> mem[1]
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* mw_i_image[2] -> mem[2]
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* mw_i_image[3] -> mem[3]
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*
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* After shifting by 1 line, it looks like this:
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* mw_i_image[0] -> mem[1]
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* mw_i_image[1] -> mem[2]
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* mw_i_image[2] -> mem[3]
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* mw_i_image[3] -> mem[0]
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* Line 3 will be computed as normal using line 2 which now
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* points to the last integral image line computed initially.
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*
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* After shifting by second line, it looks like this:
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* mw_i_image[0] -> mem[2]
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* mw_i_image[1] -> mem[3]
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* mw_i_image[2] -> mem[0]
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* mw_i_image[3] -> mem[1]
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* Line 3 will be computed as usual using line 2 which now
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* points to the last integral image line computed in the previous shift.
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*
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* Notes:
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* The mw integral must Not be shifted more than image_height - feature_height, s_lines
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* must be < feature_height-1 to keep at least one row for integral image calculations.
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*
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* This only requires (image_width * (feature_height+1) * 4) bytes. Assuming a 24x24
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* feature, the required memory is 320*25*4 (i.e. ~32KBs) instead of 320*240*4 (300KBs).
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*
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* Functions without a suffix compute/shift summed images, _sq suffix compute/shift
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* summed squared images, and _ss compute/shift both summed and squared in a single pass.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include "imlib.h"
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#include "fb_alloc.h"
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// This macro swaps two pointers.
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#define SWAP_PTRS(a, b) \
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({ __typeof__ (a) _t;\
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(_t) = ( a); \
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( a) = ( b); \
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( b) = (_t); })
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void imlib_integral_mw_alloc(mw_image_t *sum, int w, int h)
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{
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sum->w = w;
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sum->h = h;
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sum->y_offs = 0;
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sum->x_ratio = (1<<16)+1;
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sum->y_ratio = (1<<16)+1;
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sum->data = fb_alloc(h * sizeof(*sum->data), FB_ALLOC_NO_HINT);
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// swap is used when shifting the image pointers
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// to avoid overwriting the image rows in sum->data
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sum->swap = fb_alloc(h * sizeof(*sum->data), FB_ALLOC_NO_HINT);
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for (int i=0; i<h; i++) {
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sum->data[i] = fb_alloc(w * sizeof(**sum->data), FB_ALLOC_NO_HINT);
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}
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}
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void imlib_integral_mw_free(mw_image_t *sum)
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{
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for (int i=0; i<sum->h; i++) {
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fb_free(); // Free h lines
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}
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fb_free(); // Free data
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fb_free(); // Free swap
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}
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void imlib_integral_mw_scale(rectangle_t *roi, mw_image_t *sum, int w, int h)
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{
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// Set new width
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// Note: height doesn't change
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sum->w = w;
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// Reset y offset
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sum->y_offs = 0;
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// Set scaling ratios
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sum->x_ratio = (int)((roi->w<<16)/w)+1;
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sum->y_ratio = (int)((roi->h<<16)/h)+1;
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}
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void imlib_integral_mw(image_t *src, mw_image_t *sum)
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{
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// Image pointers
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typeof(*sum->data) *sum_data = sum->data;
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// Compute the first row to avoid branching
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for (int sx, s=0, x=0; x<sum->w; x++) {
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// X offset
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sx = (x*sum->x_ratio)>>16;
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, 0);
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sum_data[0][x] = s;
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}
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// Compute the remaining rows
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for (int sy, y=1; y<sum->h; y++) {
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// Y offset
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sy = (y*sum->y_ratio)>>16;
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// Sum the current row
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for (int sx, s=0, x=0; x<sum->w; x++) {
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// X offset
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sx = (x*sum->x_ratio)>>16;
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, sy);
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sum_data[y][x] = s + sum_data[y-1][x];
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}
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}
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sum->y_offs = sum->h;
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}
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void imlib_integral_mw_sq(image_t *src, mw_image_t *sum)
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{
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// Image pointers
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typeof(*sum->data) *sum_data = sum->data;
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// Compute the first row to avoid branching
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for (int sx, s=0, x=0; x<sum->w; x++) {
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// X offset
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sx = (x*sum->x_ratio)>>16;
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, 0) * IM_TO_GS_PIXEL(src, sx, 0);
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sum_data[0][x] = s;
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}
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// Compute the remaining rows
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for (int sy, y=1; y<sum->h; y++) {
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// Y offset
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sy = (y*sum->y_ratio)>>16;
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// Sum the current row
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for (int sx, s=0, x=0; x<sum->w; x++) {
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// X offset
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sx = (x*sum->x_ratio)>>16;
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, sy) * IM_TO_GS_PIXEL(src, sx, sy);
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sum_data[y][x] = s + sum_data[y-1][x];
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}
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}
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sum->y_offs = sum->h;
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}
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void imlib_integral_mw_shift(image_t *src, mw_image_t *sum, int n)
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{
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// Shift integral image rows by n lines
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for (int y=0; y<sum->h; y++) {
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sum->swap[y] = sum->data[(y+n) % sum->h];
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}
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// Swap the data and swap pointers
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SWAP_PTRS(sum->data, sum->swap);
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// Pointer to the current sum data
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typeof(*sum->data) *sum_data = sum->data;
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// Compute the last n lines
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for (int sy, y=(sum->h - n); y<sum->h; y++, sum->y_offs++) {
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// Y offset
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sy = (sum->y_offs*sum->y_ratio)>>16;
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// Sum the current row
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for (int sx, s=0, x=0; x<sum->w; x++) {
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// X offset
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sx = (x*sum->x_ratio)>>16;
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, sy);
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sum_data[y][x] = s + sum_data[y-1][x];
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}
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}
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}
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void imlib_integral_mw_shift_sq(image_t *src, mw_image_t *sum, int n)
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{
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// Shift integral image rows by n lines
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for (int y=0; y<sum->h; y++) {
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sum->swap[y] = sum->data[(y+n) % sum->h];
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}
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// Swap data and swap pointers
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SWAP_PTRS(sum->data, sum->swap);
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// Pointer to the current sum data
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typeof(*sum->data) *sum_data = sum->data;
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// Compute the last n lines
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for (int sy, y=(sum->h - n); y<sum->h; y++, sum->y_offs++) {
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// The y offset is set to the last line + 1
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sy = (sum->y_offs*sum->y_ratio)>>16;
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// Sum the current row
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for (int sx, s=0, x=0; x<sum->w; x++) {
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// X offset
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sx = (x*sum->x_ratio)>>16;
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, sy) * IM_TO_GS_PIXEL(src, sx, sy);
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sum_data[y][x] = (s + sum_data[y-1][x]);
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}
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}
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}
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void imlib_integral_mw_ss(image_t *src, mw_image_t *sum, mw_image_t *ssq, rectangle_t *roi)
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{
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// Image data pointers
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typeof(*sum->data) *sum_data = sum->data;
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typeof(*sum->data) *ssq_data = ssq->data;
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// Compute the first row to avoid branching
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for (int sx, s=0, sq=0, x=0; x<sum->w; x++) {
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// X offset
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sx = roi->x+((x*sum->x_ratio)>>16);
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, roi->y);
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sq += IM_TO_GS_PIXEL(src, sx, roi->y) * IM_TO_GS_PIXEL(src, sx, roi->y);
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sum_data[0][x] = s;
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ssq_data[0][x] = sq;
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}
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// Compute the last n lines
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for (int sy, y=1; y<sum->h; y++) {
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// Y offset
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sy = roi->y+((y*sum->y_ratio)>>16);
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// Sum the current row
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for (int sx, s=0, sq=0, x=0; x<sum->w; x++) {
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// X offset
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sx = roi->x+((x*sum->x_ratio)>>16);
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, sy);
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sq += IM_TO_GS_PIXEL(src, sx, sy) * IM_TO_GS_PIXEL(src, sx, sy);
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sum_data[y][x] = s + sum_data[y-1][x];
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ssq_data[y][x] = sq + ssq_data[y-1][x];
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}
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}
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sum->y_offs = sum->h;
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ssq->y_offs = sum->h;
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}
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void imlib_integral_mw_shift_ss(image_t *src, mw_image_t *sum, mw_image_t *ssq, rectangle_t *roi, int n)
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{
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// Shift integral image rows by n lines
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for (int y=0; y<sum->h; y++) {
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sum->swap[y] = sum->data[(y+n) % sum->h];
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ssq->swap[y] = ssq->data[(y+n) % ssq->h];
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}
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// Swap the data and swap pointers
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SWAP_PTRS(sum->data, sum->swap);
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SWAP_PTRS(ssq->data, ssq->swap);
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// Pointer to the current sum and ssq data
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typeof(*sum->data) *sum_data = sum->data;
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typeof(*ssq->data) *ssq_data = ssq->data;
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// Compute the last n lines
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for (int sy, y=(sum->h - n); y<sum->h; y++, sum->y_offs++, ssq->y_offs++) {
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// The y offset is set to the last line + 1
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sy = roi->y+((sum->y_offs*sum->y_ratio)>>16);
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// Sum of the current row
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for (int sx, s=0, sq=0, x=0; x<sum->w; x++) {
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// X offset
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sx = roi->x+((x*sum->x_ratio)>>16);
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// Accumulate row data
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s += IM_TO_GS_PIXEL(src, sx, sy);
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sq += IM_TO_GS_PIXEL(src, sx, sy) * IM_TO_GS_PIXEL(src, sx, sy);
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sum_data[y][x] = s + sum_data[y-1][x];
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ssq_data[y][x] = sq + ssq_data[y-1][x];
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}
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}
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}
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long imlib_integral_mw_lookup(mw_image_t *sum, int x, int y, int w, int h)
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{
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#define PIXEL_AT(x,y)\
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(sum->data[(y)][x])
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return PIXEL_AT(w+x, h+y) + PIXEL_AT(x, y) - PIXEL_AT(w+x, y) - PIXEL_AT(x, h+y);
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#undef PIXEL_AT
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}
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