utils.py

import time
import paddle
import math
import numpy as np
import cv2


def transform(point, center, scale, resolution, invert=False):
    """Generate and affine transformation matrix.

    Given a set of points, a center, a scale and a targer resolution, the
    function generates and affine transformation matrix. If invert is ``True``
    it will produce the inverse transformation.

    Args:
        point {paddle.tensor} -- the input 2D point
        center {paddle.tensor or numpy.array} -- the center around which to perform the transformations
        scale {float} -- the scale of the face/object
        resolution {float} -- the output resolution
        invert {bool} -- define wherever the function should produce the direct or the
        inverse transformation matrix (default: {False})
    """
    _pt = paddle.ones([3])
    _pt[0] = point[0]
    _pt[1] = point[1]

    h = 200.0 * scale
    t = paddle.eye(3)
    t[0, 0] = resolution / h
    t[1, 1] = resolution / h
    t[0, 2] = resolution * (-center[0] / h + 0.5)
    t[1, 2] = resolution * (-center[1] / h + 0.5)

    if invert:
        t = paddle.inverse(t)

    new_point = (paddle.matmul(t, _pt))[0:2]

    return new_point.astype('int32')


def crop(image, center, scale, resolution=256.0):
    """Center crops an image or set of heatmaps

    Args:
        image {numpy.array} -- an rgb image
        center {numpy.array} -- the center of the object, usually the same as of the bounding box
        scale {float} -- scale of the face
        resolution {float} -- the size of the output cropped image (default: {256.0})

    """
    """ Crops the image around the center. Input is expected to be an np.ndarray """
    ul = transform([1, 1], center, scale, resolution, True)
    ul = ul.numpy()
    br = transform([resolution, resolution], center, scale, resolution, True)
    br = br.numpy()
    if image.ndim > 2:
        newDim = np.array([br[1] - ul[1], br[0] - ul[0], image.shape[2]],
                          dtype=np.int32)
        newImg = np.zeros(newDim, dtype=np.uint8)
    else:
        newDim = np.array([br[1] - ul[1], br[0] - ul[0]], dtype=np.int)
        newImg = np.zeros(newDim, dtype=np.uint8)
    ht = image.shape[0]
    wd = image.shape[1]
    newX = np.array(
        [max(1, -ul[0] + 1), min(br[0], wd) - ul[0]], dtype=np.int32)
    newY = np.array(
        [max(1, -ul[1] + 1), min(br[1], ht) - ul[1]], dtype=np.int32)
    oldX = np.array([max(1, ul[0] + 1), min(br[0], wd)], dtype=np.int32)
    oldY = np.array([max(1, ul[1] + 1), min(br[1], ht)], dtype=np.int32)
    newImg[newY[0] - 1:newY[1],
           newX[0] - 1:newX[1]] = image[oldY[0] - 1:oldY[1],
                                        oldX[0] - 1:oldX[1], :]
    newImg = cv2.resize(newImg,
                        dsize=(int(resolution), int(resolution)),
                        interpolation=cv2.INTER_LINEAR)
    return newImg