import cv2
import numpy as np


def sliding_window(image, start, stepSize, windowSize):
    width = max(1, start[2] - windowSize[0])
    height = max(1, start[3] - windowSize[1])
    # slide a window across the image
    for y in xrange(start[1], start[1] + height, stepSize):
        for x in xrange(start[0], start[0] + width, stepSize):
            h = min(windowSize[1], start[3])
            w = min(windowSize[0], start[2])
            center = (min(x + w / 2, image.shape[1]), min(y + h / 2, image.shape[0]))
            x = max(0, int(center[0] - windowSize[0] / 2))
            y = max(0, int(center[1] - windowSize[1] / 2))
            # yield the current window
            yield (x, y, image[y:y + windowSize[1], x:x + windowSize[0]])


def pyramid(image, minSize):
    yield image

    if image.shape[0] < minSize[0] and image.shape[1] < minSize[1]:
        # image too small - upscaling until we hit window level
        image = cv2.pyrUp(image)

        while (image.shape[0] <= minSize[0] or image.shape[1] <= minSize[1]):
            yield image
            image = cv2.pyrUp(image)
    else:
        # image too big - downscaling until we hit window level
        image = cv2.pyrDown(image)

        while (image.shape[0] >= minSize[0] or image.shape[1] >= minSize[1]):
            yield image
            image = cv2.pyrDown(image)


# Malisiewicz et al.
def non_max_suppression_fast(boxes, overlapThresh):
    # if there are no boxes, return an empty list
    if len(boxes) == 0:
        return []

    # if the bounding boxes integers, convert them to floats --
    # this is important since we'll be doing a bunch of divisions
    if boxes.dtype.kind == "i":
        boxes = boxes.astype("float")

    # initialize the list of picked indexes
    pick = []

    # grab the coordinates of the bounding boxes
    x1 = boxes[:, 0]
    y1 = boxes[:, 1]
    x2 = boxes[:, 2]
    y2 = boxes[:, 3]

    # compute the area of the bounding boxes and sort the bounding
    # boxes by the bottom-right y-coordinate of the bounding box
    area = (x2 - x1 + 1) * (y2 - y1 + 1)
    idxs = np.argsort(y2)

    # keep looping while some indexes still remain in the indexes
    # list
    while len(idxs) > 0:
        # grab the last index in the indexes list and add the
        # index value to the list of picked indexes
        last = len(idxs) - 1
        i = idxs[last]
        pick.append(i)

        # find the largest (x, y) coordinates for the start of
        # the bounding box and the smallest (x, y) coordinates
        # for the end of the bounding box
        xx1 = np.maximum(x1[i], x1[idxs[:last]])
        yy1 = np.maximum(y1[i], y1[idxs[:last]])
        xx2 = np.minimum(x2[i], x2[idxs[:last]])
        yy2 = np.minimum(y2[i], y2[idxs[:last]])

        # compute the width and height of the bounding box
        w = np.maximum(0, xx2 - xx1 + 1)
        h = np.maximum(0, yy2 - yy1 + 1)

        # compute the ratio of overlap
        overlap = (w * h) / area[idxs[:last]]

        # delete all indexes from the index list that have
        idxs = np.delete(idxs,
                         np.concatenate(([last], np.where(overlap > overlapThresh)[0])))

    # return only the bounding boxes that were picked using the
    # integer data type
    return boxes[pick].astype("int")


#  Felzenszwalb et al.
def non_max_suppression_slow(boxes, overlapThresh):
    # if there are no boxes, return an empty list
    if len(boxes) == 0:
        return []

    # initialize the list of picked indexes
    pick = []

    # grab the coordinates of the bounding boxes
    x1 = boxes[:, 0]
    y1 = boxes[:, 1]
    x2 = boxes[:, 2]
    y2 = boxes[:, 3]

    # compute the area of the bounding boxes and sort the bounding
    # boxes by the bottom-right y-coordinate of the bounding box
    area = (x2 - x1 + 1) * (y2 - y1 + 1)
    idxs = np.argsort(y2)

    # keep looping while some indexes still remain in the indexes
    # list
    while len(idxs) > 0:
        # grab the last index in the indexes list, add the index
        # value to the list of picked indexes, then initialize
        # the suppression list (i.e. indexes that will be deleted)
        # using the last index
        last = len(idxs) - 1
        i = idxs[last]
        pick.append(i)
        suppress = [last]

        # loop over all indexes in the indexes list
        for pos in xrange(0, last):
            # grab the current index
            j = idxs[pos]

            # find the largest (x, y) coordinates for the start of
            # the bounding box and the smallest (x, y) coordinates
            # for the end of the bounding box
            xx1 = max(x1[i], x1[j])
            yy1 = max(y1[i], y1[j])
            xx2 = min(x2[i], x2[j])
            yy2 = min(y2[i], y2[j])

            # compute the width and height of the bounding box
            w = max(0, xx2 - xx1 + 1)
            h = max(0, yy2 - yy1 + 1)

            # compute the ratio of overlap between the computed
            # bounding box and the bounding box in the area list
            overlap = float(w * h) / area[j]

            # if there is sufficient overlap, suppress the
            # current bounding box
            if overlap > overlapThresh:
                suppress.append(pos)

        # delete all indexes from the index list that are in the
        # suppression list
        idxs = np.delete(idxs, suppress)

    # return only the bounding boxes that were picked
    return boxes[pick]
