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