im2col.c
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#include "im2col.h"
#include <stdio.h>
float im2col_get_pixel(float *im, int height, int width, int channels,
int row, int col, int channel, int pad)
{
row -= pad;
col -= pad;
if (row < 0 || col < 0 ||
row >= height || col >= width) return 0;
return im[col + width*(row + height*channel)];
}
//From Berkeley Vision's Caffe!
//https://github.com/BVLC/caffe/blob/master/LICENSE
void im2col_cpu(float* data_im,
int channels, int height, int width,
int ksize, int stride, int pad, float* data_col)
{
int c,h,w;
int height_col = (height + 2*pad - ksize) / stride + 1;
int width_col = (width + 2*pad - ksize) / stride + 1;
int channels_col = channels * ksize * ksize;
for (c = 0; c < channels_col; ++c) {
int w_offset = c % ksize;
int h_offset = (c / ksize) % ksize;
int c_im = c / ksize / ksize;
for (h = 0; h < height_col; ++h) {
for (w = 0; w < width_col; ++w) {
int im_row = h_offset + h * stride;
int im_col = w_offset + w * stride;
int col_index = (c * height_col + h) * width_col + w;
data_col[col_index] = im2col_get_pixel(data_im, height, width, channels,
im_row, im_col, c_im, pad);
}
}
}
}