function [batches, batch_padding] = rcnn_extract_regions(im, boxes, rcnn_model)
% [batches, batch_padding] = rcnn_extract_regions(im, boxes, rcnn_model)
%   Extract image regions and preprocess them for use in Caffe.
%   Output is a cell array of batches.
%   Each batch is a 4-D tensor formatted for input into Caffe:
%     - BGR channel order
%     - single precision
%     - mean subtracted
%     - dimensions from fastest to slowest: width, height, channel, batch_index
%
%   im is an image in RGB order as returned by imread
%   boxes are in [x1 y1 x2 y2] format with one box per row

% AUTORIGHTS
% ---------------------------------------------------------
% Copyright (c) 2014, Ross Girshick
% 
% This file is part of the R-CNN code and is available 
% under the terms of the Simplified BSD License provided in 
% LICENSE. Please retain this notice and LICENSE if you use 
% this file (or any portion of it) in your project.
% ---------------------------------------------------------

% convert image to BGR and single
im = single(im(:,:,[3 2 1]));
num_boxes = size(boxes, 1);
batch_size = rcnn_model.cnn.batch_size;
num_batches = ceil(num_boxes / batch_size);
batch_padding = batch_size - mod(num_boxes, batch_size);

crop_mode = rcnn_model.detectors.crop_mode;
image_mean = rcnn_model.cnn.image_mean;
crop_size = size(image_mean,1);
crop_padding = rcnn_model.detectors.crop_padding;

batches = cell(num_batches, 1);
%for batch = 1:num_batches
parfor batch = 1:num_batches
  batch_start = (batch-1)*batch_size+1;
  batch_end = min(num_boxes, batch_start+batch_size-1);

  ims = zeros(crop_size, crop_size, 3, batch_size, 'single');
  for j = batch_start:batch_end
    bbox = boxes(j,:);
    crop = rcnn_im_crop(im, bbox, crop_mode, crop_size, ...
        crop_padding, image_mean);
    % swap dims 1 and 2 to make width the fastest dimension (for caffe)
    ims(:,:,:,j-batch_start+1) = permute(crop, [2 1 3]);
  end

  batches{batch} = ims;
end